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• Wetlands topsoil can sequester more C than farmlands and forestlands. • Soil water content was important factor affecting microbial abundance and enzyme activity. • Higher soil water content can increase soil C storage by stimulating C fixing enzyme activity. • Soil C storage were negatively driven by soil bacterial abundance under different land-use. Soil carbon storage plays a crucial role in mitigating the climate warming and is significantly impacted by the land use pattern. To better understand soil carbon stability and the underlying microbial mechanism, based on qPCR, ELISA, and fluorescence techniques, the effects of land use changes on soil microbial abundance, enzyme activity, and soil carbon storage were investigated in the complex ecosystems of cropland, forestland, and wetland along three typical river (Wolvlan river, Bielahong river, Wusuli river) basin in Sanjiang Plain, China. We hypothesised that croplands soil carbon storage is lower than forestlands and wetlands, which is regulated by soil water content, microbe and enzyme activity. Results showed that topsoil TC in wetlands (85.54 mg·g−1) was higher than those in croplands (33.46 mg·g−1) and forestlands (46.13 mg·g−1). Topsoil water content increased 73.90 % and 71.64 % in wetlands than in farmland and forestlands, respectively. Additionally, reclamation diminished topsoil carbon storage. In croplands, soil dissolved organic carbon, microbial biomass carbon, microbial biomass nitrogen, available nitrogen, bacterial abundance, and soil enzymes (i.e., RubisCO, β-glucosidase, cellobiohydrolase, 1,4-N-acetylglucosaminidase and acid phosphatase) activities were substantially lower than those in wetlands. Structural equation modeling showed that soil carbon storage was positively related to soil water content and RubisCO activity but negatively related to soil bacterial abundance. Soil water content had the largest standardised total positive effect coefficient and indirectly influenced soil carbon storage by affecting RubisCO activity. Soil depth had a greater effect on SMC, hydrolase and site had a greater effect on bacteria and fungi abundance. The results highlight that the alteration of carbon fixing enzyme activity by soil water content is a crucial mechanism for soil carbon sequestration in response to land-use change. Management strategies that conserve natural wetlands, increase soil water content and minimize land disturbance would be effective in maintaining soil carbon stocks. [ABSTRACT FROM AUTHOR]

• Hillslope erosion dynamic model integrating vegetation effect was established. • Unified baseline parameters were obtained across different land uses. • Effect of vegetation on soil detachment and sediment transport was revealed. • Contribution rates of vegetation to sediment reduction along slopes were quantified. Developing a process-based soil erosion model that comprehensively considers the effects of vegetation is complex but crucial for evaluating sediment reduction during vegetation restoration. Current understanding of the effect of vegetation on sediment reduction along hillslopes across different land uses is limited. In this paper, we developed a dynamic model of hillslope erosion that integrates the effects of vegetation on soil detachability and hydrodynamics (VED) based on the feedback mechanism between soil detachment and sediment transport. The VED was calibrated and validated with runoff plot data for woodland, grassland, and farmland in the Wuding, Yan, Jing and Wei Rivers of the Loess Plateau in China. Unified baseline parameters and decay coefficients of vegetation were obtained. The model validation results indicated that the coefficient of determination, Nash–Sutcliffe simulation efficiency and relative error ranged from 0.59 to 0.99, 0.56 to 0.90, and −45.99 % to 46.36 %, respectively. The decay coefficients for soil detachment capacity (Φ), sediment transport capacity (T c), and the sediment reduction effect of vegetation exhibited the following order: woodland > grassland > farmland. Compared with VED, existing process-based soil erosion models failed to effectively characterize the influence of vegetation on Φ and T c on the Loess Plateau, with differences of several orders of magnitude. The individual contributions of runoff, soil detachability, and hydrodynamics with vegetation impact on sediment yield were quantified by VED. The contribution rates of vegetation to sediment reduction decreased gradually with increasing slope length because the soil detachment capacity of bare slopes exceeded that of vegetated slopes, resulting in a faster increase in sediment yield. The contribution rates of vegetation to sediment reduction for woodland, grassland, and farmland with 20 %–60 % vegetation covers were 66.75 %–99.95 %, 57.43 %–99.63 %, and 27.91 %–88.63 % in the boundary conditions of this study, respectively. The results reveal the potential for integrating VED into other distributed watershed hydrological and sediment models to assess the effects of vegetation restoration on sediment reduction at a watershed scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rainfall and temperature both had a significant effect on forest land. • Annual rainfall and grassland area contributed the most to soil conservation. • Land use had a greater direct impact on soil conservation than climate factors. • Land use, rainfall, and temperature had threshold effects on soil conservation. In the Loess Plateau, enhancing the function of soil conservation (SC) is essential for maintaining ecological sustainability. Land use (LU), rainfall, and temperature might all have a big influence on SC. In this study, we applied the InVEST model to assess the SC of a typical city, Yan'an, in 1990, 2000, 2010, and 2020. Effects of LU, rainfall, and temperature changes on SC were examined using correlation analysis, redundancy analysis (RDA), regression analysis, and frequency ratio analysis. The findings indicated that farmland (FC), forest land (FL), and grassland (GL) were Yan'an City's main LU types. The expansion of FL and GL areas has come at the expense of the FC areas, partly due to the "Grain for Green" Project, and this change has accelerated considerably since 2000. The total amount of SC in 1990, 2000, 2010, and 2020 generally showed a decreasing and then increasing trend, which was 0.96, 0.87, 1.22, and 1.39 billion tons respectively. In the research region, temperature, rainfall, and LU changes occurred all at once. The FL region was quite consistent with the geographical distribution of areas with low temperatures and heavy rainfall. The results of correlation analysis and RDA indicated that GL area and annual rainfall (PY) were the main causes of SC (p < 0.01). A strong connection (r = 0.63, p < 0.01) was also seen between the daily temperature range (ΔT) and SC. Increased LU-type area, rainfall, and temperature improved SC with a threshold range. Calculated by regression analysis, it recommended the FL ≤ 11040 km2, GL ≥ 14720 km2, and FC ≤ 7360 km2 in Yan'an City. Rainfall and temperature showed no significant pattern and were difficult to regulate by human intervention. The improvement of SC should focus on adjusting the LU structure under the existing ecological planning. Accepting some degrees of uncertainty, our findings provide insights into how possible LU, rainfall, and temperature will affect SC. It's crucial both for future regional management and ecological sustainability development. [ABSTRACT FROM AUTHOR]

• Land use types determined deep soil water redistribution. • Soil moisture in abandoned land was strongly affected by rainfall. • Decreased rainfall and soil drying reduced the growth of forage and shrubs. • Farmland in terraces and abandoned land on slopes were the ideal use types. The land-use change affects soil hydrological processes in semi-arid areas. Investigating the impact of precipitation change on soil moisture in different land use types (LUTs) is conducive to water resource management and ecological restoration. The volumetric water content (VWC) at 0–300 cm soil profile, meteorology data, and vegetation aboveground biomass were continuously observed from 2018 to 2022 in five terraced and three sloped LUTs. The results showed that soil moisture was affected by precipitation, vegetation, antecedent soil water, soil properties, and artificial management measures. There were significant differences in soil moisture among these land use types (P < 0.05), with the priority order of multi-year profile average VWC at 0–300 cm depth was farmland in the slope (FAS) (0.22 ± 0.01 cm3 cm−3) > bare land in the terrace (BAT) and farmland in the terrace (FAT) (0.19 ± 0.01 cm3 cm−3) > abandoned land in the slope (ABS) (0.18 ± 0.02 cm3 cm−3) > abandoned land in the terrace (ABT) (0.13 ± 0.02 cm3 cm−3) > forage land in the slope (FOS) (0.12 ± 0.02 cm3 cm−3) > forage land in the terrace (FOT) and shrubland in the terrace (SHT) (0.10 ± 0.01 cm3 cm−3). Except for BAT, soil water storage (SWS) in other LUTs decreased in 0–300 cm soil profile from 2018 to 2022. There were no or slight soil desiccations in FAS, BAT, ABS, and FAT, moderate soil desiccation in ABT, and serious soil desiccation in FOS, FOT, and SHT. The VWC, SWS, and soil desiccation index (SDI) of all LUTs were positively correlated with precipitation, especially at 0–100 cm depth. Precipitation threshold response to soil desiccation alleviation was determined to be 98–116 mm month−1. Moreover, aboveground biomass of FOT, ABT, and SHT exhibited a significant correlation with both soil moisture and precipitation (P < 0.05). Therefore, forage lands and shrublands have adverse effects on the mitigation of deep soil desiccation with decreasing rainfall. This study recommended farmland in the terrace and abandoned land in the slope for soil and water conservation and sustainable ecological restoration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amino sugars are chosen as biomarkers of microbial necromass in aggregate soils. • NW conversion to FL or CL increases the contribution of aggregate MNC to SOC. • FNC are the main contributor to microbial necromass in estuarine soils. • Enhanced perturbation induces the enrichment of BNC to smaller-size aggregates. • pH and SMC affect the aggregate-associated MNC accumulation by mediating the MBC. Microbial necromass carbon (MNC), as an important component of the soil organic carbon (SOC) pool in natural environments, has increasingly gained significant attention in recent years. However, the redistribution pattern of microbial necromass in aggregate fractions of estuarine soils induced by human activity still remain unclear. In this study, we assessed the effect of land use conversion on the redistribution and accumulation patterns of aggregate-associated MNC in estuarine wetland soils on the Pearl River estuary of China. Typical soil samples in 0–30 cm profiles under different land uses [Natural Wetland (NW), Farmland (FL), and Construction Land (CL)] were analyzed. The results showed that the NW conversion to FL and then CL contributed to the continuous losses of SOC, however, the aggregate-associated MNC content was higher in FL and lower in CL compared to NW. The MNC contribution to total SOC in aggregate fractions gradually increased from NW (16.41 % − 23.62 %) to CL (23.87 % − 30.98 %) and then FL (34.62 % − 38.83 %) in profiles. Fungal necromass C was the primary contributor to the total MNC in each aggregate fraction. In NW, the MNC was mainly present in large aggregate size, however, the MNC was gradually enriched into smaller size aggregates, especially for the bacterial necromass C, after the conversion from NW to FL or CL. Microbial biomass carbon had a direct and positive effect on the MNC in soil aggregates under different land uses, except for in silt + clay fraction from NW. Moreover, pH and soil moisture content were two key variables affecting the MNC content and accumulation by mediating the microbial biomass of different land uses, while the dominate factors controlling the MNC accumulation varied with size fractions in aggregates. Our results emphasize the influence of land use conversion on the soil aggregate-associated MNC accumulation in estuarine wetland. [ABSTRACT FROM AUTHOR]

• Classification of flood events into typhoon and non-typhoon rainstorm floods. • Key parameters in HEC-HMS model were systematically different for the two types of floods. • Impact of land use change on typhoon floods was smaller than that of non-typhoon floods. • Frequency distribution of the mixture flood series with the effect of land use change. There are two major types of rainstorms in the Asia-Pacific region –typhoon induced rainstorm and non-typhoon rainstorm. This study investigated and separated the different flood responses to these two types of rainstorms, based on a scheme that combined the classification of typhoon and non-typhoon rainstorm floods, the simulation from a distributed hydrological model, and a method to forward restore the impact of land use change on flood frequency analysis. For flood events in a typical basin on the southeast coast of China, the flood characteristics in response to typhoon and non-typhoon rainstorms were significantly different in three aspects: (1) The key parameters in the HEC-HMS model were systematically different. The initial loss and wave velocity of the model were apparently larger for the typhoon rainstorm flood than for the non-typhoon rainstorm flood. (2) The impacts of land use change were different, with smaller effect on typhoon induced floods than on non-typhoon floods under the same magnitude of flood peak flow. (3) Classification of two types of floods resulted in more reasonable frequency analysis affected with the land use change because the annual maximum flood series is the mixture of typhoon and non-typhoon rainstorms. Frequency analysis for the forward-restored mixture flood series showed that the land use change with the decrease in the area of forest land and the increase of garden and construction land resulted in the increase of the mean maximum flow from 2266.6 to 2510.19 m3/s, but the values of coefficient of variation were slightly altered, the ratio of skewness coefficient to variation coefficient were unchanged. The results provide new ideas and methods for a deeper understanding of the impact of land use change on flooding in typhoon and non-typhoon co-action regions. [ABSTRACT FROM AUTHOR]

• Spatial variations in soil erodibility was quantified by indicators in karst hillslope. • Identify the predominant factors affecting spatial variations in soil erodibility. • Land use and slope position had great effects on near-surface soil characteristics. • CSEI varied with land use and slope position, and affected by soil characteristics. Land use type and slope position have a considerable impact on soil properties and thus likely influence soil erodibility. Soil erosion on karst hillslopes in South China is still serious due to the high intensity of human activities and fragile ecological environment. Nevertheless, the potential effects of land use type and slope position on soil erodibility indicators in karst areas are still unclear. This study was conducted to investigate the spatial variations in soil erodibility indicators, namely, the saturated hydraulic conductivity (K S), mean weight diameter (MWD), soil structural stability (SSI), soil erodibility K factor, soil organic carbon content (SOC), and a comprehensive soil erodibility index (CSEI) for three typical land uses and three slope positions on a karst hillslope. The results showed that K S , MWD , SSI , K factor, SOC and CSEI varied significantly with land use type and slope position. The measured K S , MWD , SSI , K factor and SOC at the nine tested sites displayed a similar trend with soil depth. SOC , MWD and SSI contributed more to the CSEI , with contributions of 27.9%, 25.9% and 25.9%, respectively. K S and K factor contributed less to the CSEI , with contributions of 17.7% and 2.5%, respectively. Woodland is most susceptible to erosion on upper, cropland on middle and grassland on lower slope positions according to the values of CSEI. There were significant positive correlations among sand content, bulk density and CSEI , and there were significant negative correlations among clay content, silt content, root mass density, SOC and CSEI. The changes in soil properties and soil erodibility indicators with land use type and slope position led to the differences in the CSEI. The results provide valuable information for policymakers to select appropriate land use types to mitigate soil erosion and thus improve the healthy development of the ecological environment on karst slopes. Moreover, the results have crucial implications for understanding the mechanism of the spatial variation in soil erosion of karst hillslopes in Southwest China. [ABSTRACT FROM AUTHOR]

• The mean soil organic carbon (SOC) content in agroecosystem of Eastern China was 18.24 g kg−1. • The SOC content of planted forest > cropland > grassland in the total study area. • The SOC value of grassland was higher than cropland in North China due to excessive mechanized operation. • The random forest hybrid model exhibited higher comprehensive performance in SOC prediction. • Our predictions were much more detailed and accurate than the existing SOC content maps. Soil organic carbon (SOC) plays a key role in soil function, ecosystem services, and the global carbon cycle. Large SOC stocks accumulate in agroecosystems, but the estimates of SOC distribution and magnitude in agroecosystems still have large uncertainties in global products. Based on multiple high-resolution environmental variables (terrain derived from digital elevation model, climate and organism from Landsat 8 OLI) and 369 observed soil samples from 2019 to 2021, two machine learning methods, random forest (RF) and support vector machine (SVM) models, were used to estimate the content and spatial distribution of SOC in agroecosystems of Eastern China. We proposed a hybrid model in which the optimal predictors of SOC were selected for different land use types (cropland, planted forest and grassland), and it aimed to improve the performance of machine learning. Our results showed that (1) the hybrid models performed better than the global models, and the Random forest-Hybrid (RF-Hybrid) model led to the highest prediction accuracy, with a validation R2 of 0.65 and RMSE of 5.76 g kg−1. (2) The SOC content in the agroecosystems of Eastern China among different land use types ranked in the following order: planted forest (19.92 g kg−1) > cropland (17.51 g kg−1) > grassland (17.30 g kg−1). However, in North China, the SOC content in cropland (14.04 g kg−1) was much lower than that in planted forest (17.21 g kg−1) and grassland (17.07 g kg−1), which was caused by excessive mechanized operation. (3) The agroecosystem in Northeast China presented the highest mean SOC content (26.55 g kg−1) due to low temperature. (4) Our estimations (R2 = 0.53, RMSE = 6.74 g kg−1, 30-m resolution) were more detailed and precise than the existing global SOC maps (Soil Grids: R2 = 0.26, RMSE = 12.44 g kg−1, 250-m resolution; HWSD: R2 = 0.06, RMSE = 41.07 g kg−1, 1000-m resolution). The results may improve the accuracy of agroecosystem carbon mapping and contribute to SOC assessments in agricultural ecosystems. [ABSTRACT FROM AUTHOR]

• Facility lands were considered to be greater carbon sinks compared to other land uses. • The most stable type of organic carbon is in facility land, and the most unstable is in grasslands. • Changes in land use have a significant impact on organic carbon fractions and carbon mineralization. Soil carbon is an essential component that influences soil health and agronomic productivity, and land-use practices significantly impact soil carbon stocks. In this study, the researchers investigated the impact of various land-use types (farmland, orchards, grasslands, and facility lands) on soil organic carbon (SOC) fractions in the Qaidam Basin of China's Qinghai-Tibet Plateau. The soil samples were taken from the 0–10 and 10–20 cm depths. The particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) fractions of various land uses have been measured. The results revealed that grasslands had the greatest POC/SOC ratio (0.59), with POC accounting for the majority of the SOC fraction. In contrast, all other land-use types (facility land, orchards, and farmland) had greater MAOC/SOC ratios than POC/SOC. The facility land had the highest SOC content (17.75 g kg−1), and orchard had the lowest (8.51 g kg−1). The grassland had the highest POC content (9.82 g kg−1) at a depth of 0–10 cm. The trend for MAOC content among the various land-use types was facility lands > farmlands > grasslands > orchards. The soil pH was also observed to be moderately alkaline, with an average of 8. The orchard has the highest bulk density (BD), measuring 1.38 g cm−3. The grasslands contained the highest amount of total nitrogen (TN) (2.2 g kg−1) while the agricultural fields contained the highest amount of total phosphorus (TP) (1.16 g kg−1). In addition, facility lands showed the highest level of microbial activity compared to other land-use types. According to the findings, SOC, POC, and MAOC fractions had considerably positive associations with TN and microbial biomass carbon (MBC), but were significantly negatively associated with metabolic CO 2. The findings imply that different land-use types can have a considerable impact on the quality and amount of soil organic carbon, which has consequences for soil health and ecosystem processes. The findings also highlight the significance of long-term land management practices that promote the preservation and enhancement of soil organic carbon in various land-use systems. [ABSTRACT FROM AUTHOR]

Forest secondary succession and conversion to an agricultural use are rapidly altering tropical forests, and this alteration has consequences on soil microbial communities. Using high-throughput sequencing of 16S rRNA genes and internal transcribed spacer regions, we compared bacteria and fungi community composition and diversity in soils between the three stages of forest succession (primary forest, PF; secondary forest, SF; pioneer plant community dominated by Macaranga denticulate trees, PP) and two agricultural drylands (rubber plantation, RP; Plukenetia volubilis plantation, PV) in Xishuangbanna, a tropical region of China, and identified the factors associated with the shift in community composition across the five land-use types. The results indicated that the most abundant bacterial genera ( Bacillus , Kitasatospora , Nitrospira and Streptacidiphilus ) were found at differentially relative abundances among the five land-use types. Through the analysis of indicator species, several bacterial species were significantly associated with the PP site; one to four species were significantly associated to the other sites. Strikingly, almost all fungal genera had site-specific characteristic. Soil properties, especially pH and available P and K, were associated with microbial community composition. Across the three stages of forest succession, bacterial and fungal richness and bacterial alpha diversity had the lowest levels in the earliest stage (PP), but there were no significant differences in microbial richness or diversity between the late stages (PF vs. SF). Compared to PF and SF with their similar bacterial and fungal diversity, the agricultural drylands (RP and PV) had higher bacterial richness but lower fungal richness, indicating that both PF and SF can act as reservoirs for the recolonisation of forest-associated microbes. Overall, these results showed a distinct difference in soil microbe taxonomic composition, especially in fungi, among the various land-use types, even at a very small geographical scale (<4 km), but no great difference of microbial diversity was found between the late stages of forest succession and agricultural drylands. Tropical forest succession and forest conversion to agricultural drylands strongly affect the distribution of microbial species, whereas microbial diversity may not always tightly follow the same successional trajectories. [ABSTRACT FROM AUTHOR]

Landslides are a manifestation of slope instability causing different kinds of damage affecting life and property. Therefore, high-performance-based landslide prediction models are useful to government institutions for developing strategies for landslide hazard prevention and mitigation. Development of data mining based algorithms shows that high-performance models can be obtained using ensemble frameworks. The primary objective of this study is to investigate and compare the use of current state-of-the-art ensemble techniques, such as AdaBoost, Bagging, and Rotation Forest, for landslide susceptibility assessment with the base classifier of J48 Decision Tree (JDT). The Guangchang district (Jiangxi province, China) was selected as the case study. Firstly, a landslide inventory map with 237 landslide locations was constructed; the landslide locations were then randomly divided into a ratio of 70/30 for the training and validating models. Secondly, fifteen landslide conditioning factors were prepared, such as slope, aspect, altitude, topographic wetness index (TWI), stream power index (SPI), sediment transport index (STI), plan curvature, profile curvature, lithology, distance to faults, distance to rivers, distance to roads, land use, normalized difference vegetation index (NDVI), and rainfall. Relief-F with the 10-fold cross-validation method was applied to quantify the predictive ability of the conditioning factors and for feature selection. Using the JDT and its three ensemble techniques, a total of four landslide susceptibility models were constructed. Finally, the overall performance of the resulting models was assessed and compared using area under the receiver operating characteristic (ROC) curve (AUC) and statistical indexes. The result showed that all landslide models have high performance (AUC > 0.8). However, the JDT with the Rotation Forest model presents the highest prediction capability (AUC = 0.855), followed by the JDT with the AdaBoost (0.850), the Bagging (0.839), and the JDT (0.814), respectively. Therefore, the result demonstrates that the JDT with Rotation Forest is the best optimized model in this study and it can be considered as a promising method for landslide susceptibility mapping in similar cases for better accuracy. [ABSTRACT FROM AUTHOR]

Composition and stability of soil organic matter (SOM) affect the sustenance and productivity of soil over the long-term. This issue is particularly important for karst regions in China where the water supply and fertilizer use are limiting factors. Here, we used four indicators to evaluate changes in the composition and stability of SOM quantitatively in five main land-use types in karst area, including primary forest [PF], 15-year secondary forest [SF], grazing secondary forest [GF], abandoned farmland [AF] and farmland [FL]. We collected soil samples at a depth of 0–20 cm to conduct the analyses. Four indicators were used: soil physical and chemical properties, active organic carbon (C), humus C composition, and SOM functional groups. Our results showed that the content of SOM, total nitrogen, and easily oxidized organic C at 0–20 cm soil depth differed among the five land-use types ( P < 0.05). For humic acid C concentration, the land-use types were ordered as: SF > PF > GF > FL > AF. Solid-state 13 C NMR spectra showed that the highest ratio of Alkyl C/O-alkyl C was in AF, while the lowest was in SF. Overall, the comprehensive quality of SOM in different land-use types was PF (setting 100%) > SF (83.1%) > GF (58%) > AF (30.9%) > FL (29.9%). For karst areas, we suggest that farmlands in sloping area should be converted back to forests, with only moderate grazing being permitted, whereas farmlands in the plains should implement grain-forage rotation and grain-soybean rotation to meet the needs of the growing population and economic development. In conclusion, our findings provide a scientific basis from which to delineate rational land-use types for different land (geographical and geological) formations. [ABSTRACT FROM AUTHOR]

Fixed dunes are indicators of successful recovery of desertified land after several years of vegetation restoration. Land use profoundly influences soil properties; however, the effects of changes in land use, after the dunes are fixed, on soil physical, chemical and microbial biomass properties are still unclear. This study investigates the soil physical and chemical properties and soil microbial biomass in a desertified land located in the Xiaojihan desertification control station in northern Shaanxi province, where land use changed from shrub land to arboreal land, arable land and nursery garden. No significant changes in soil properties were found when shrubland was changed to arboreal land. However, changing the fixed desertified land from shrub land to arable land and nursery garden decreased soil porosity, but significantly increased soil bulk density (BD), soil organic matter (SOM), cation exchange capacity (CEC), total nitrogen (TN) and available nutrients (N, P, K). Soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP), as well as microbial quotient (MBC/SOC, MBN/TN, MBP/TP), decreased significantly. No significant changes were detected in soil texture, total phosphorus (TP) and total potassium (TK). Results of this study indicated that agricultural land use can improve the fertility of fixed desertified land; however, soil microbial biomass could decrease. Therefore, conversion of fixed dunes to agricultural usage is full of risks. [ABSTRACT FROM AUTHOR]

Land use change is affected by many driving factors such as the economy, population, and government policy. This study investigated the relationship between government policy and land use change to develop an understanding applicable to the formulation of strategies for sustainable land use. The Lijiang River Basin in the Guangxi Zhuang Autonomous Region in southern China was selected for this study. The predicted characteristics of land use change were explored using the CLUE-S numerical model and logistic regression. Using Landsat remote sensing imagery as source data, we simulated the tendency of land use change from 1993 to 2020 under two scenarios: a Natural Growth Scenario (NS) and a Government Intervention Scenario (GS), and we analyzed the possible social driving factors. The results revealed that from 1993 to 2015, both construction and cultivated land have shown a tendency of areal increase. Water and woodland areas both decreased from 1993 to 2006 but then they increased dramatically from 2006 to 2015. Shrubland areas increased from 1993 to 2006 but decreased slightly from 2006 to 2015. The CLUE-S model was used to predict the spatial patterns of land use for 2020. It showed that under the NS, the areas of construction and cultivated land increased, while the areas of other land uses decreased. Under the GS, the areas of construction land, woodland, cultivated land, and water all increased, while the areas of the others declined. Furthermore, the area of woodland decreased for every county under the NS, but areas of woodland expansion were located in Lingchuan and Lingui counties under the GS. Hotspots of cultivated land occurred in Lingchuan County under the NS and in Xingan County under the GS. Water area decreased in every county under the NS, whereas increases in water areas occurred in Lingchuan and Guilin counties under the GS. Construction land expanded in Lingchuan County under the NS and in Guilin County under the GS. The Returning Farmland to Forest Program could be considered a successful addition to the eco-environmental policies implemented in the Lijiang River Basin. [ABSTRACT FROM AUTHOR]

In recent decades, temperate steppe have become seriously degraded, and rest grazing or moderate grazing approaches have been widely adopted since 1998 to restore degraded grasslands in northern China. The importance of choosing an appropriate grazing management regime for optimizing carbon sequestration in light of climate change or promoting other multiple ecological benefits of grassland ecosystems to humankind have long been recognized. In particular, the various uncertainties in plant and soil properties affected by grazing management require clarification. In this study, we selected fifteen blocks within three kinds of grazing management practices, including free grazing, warm-season grazing, and rest grazing, to test the responses of plant and soil properties to grazing management. The results showed that the species richness, the Shannon-Wiener index, and the proportion of forb functional group were higher for the warm-season grazing sites than for the free grazing sites. Soil bulk density, pH, the Pielou evenness index and the proportion of legume functional groups showed no difference among the three kinds of grazing managements. However, aboveground biomass, root biomass, canopy cover, and height of the vegetation community were larger in the rest grazing sites than in the free grazing sites. Soil organic carbon and total nitrogen contents decreased as management intensity increased, with the lowest and highest values occurring in the free grazing and rest grazing sites, respectively. Furthermore, soil organic carbon and total nitrogen contents were correlated positively with root biomass. Rest grazing was a suitable management strategy for carbon and nitrogen sequestrations, while moderate grazing was a suitable management strategy for diversity conservation in the temperate steppe, in northern China. [ABSTRACT FROM AUTHOR]

[Display omitted] • Land use/cover change characterized by cropland loss and expansion of other lands. • Urbanization grew exponentially, while other land changes peaked in 1995–2005. • Land use/cover had two conversion patterns before and after 175 m impounding. • Cropland will drop by 1094 km2 by 2030, which is mainly converted to built-up land. • Most land use/cover changes are altitude-sensitive and supplemented by other factors. Coordination of economic development and ecological conservation in land use/cover (LULC) remains a great challenge, particularly in eco-fragile areas. A holistic understanding of LULC change is a premise for coordinating the conflict. In this study, we elucidated the spatiotemporal evolution of LULC in China′s typical eco-fragile area-the Three Gorges Reservoir area during different periods of Gezhou Dam-Three Gorges Dam (GZD-TGD) construction and impoundment (1982–2020), and predicted LULC in 2030 with the patch-generating land-use simulation (PLUS) model. In 1982–2020, the LULC changes mainly included cropland loss, forestland restoration, urban development and water expansion, among which cropland decreased by 4688 km2, while forestland, built-up land and water increased by 3273, 1002 and 272 km2, respectively. For most LULC types, the most significant change occurred in 1995–2005, whereas the built-up land increased exponentially from 0.41% to 5.06% during the entire study period, which was mainly derived from cropland. Under a natural development scenario, cropland would drop continuously by 1094 km2 till 2030. In addition, there were significant interconversions between various land types before GZD-TGD impoundment of 175 m, particularly vegetation, while only built-up land increased dramatically by occupying 2.66% of cropland thereafter. Contributions of various driving factors to LULC changes varied across different periods due to the direct/indirect effects of GZD-TGD construction and impoundment. Most changes in LULC were elevation-sensitive, and supplemented by other factors. Furthermore, the expansion of various LULC types tended to occur more often in areas with low elevations and gentle slopes. The results may assist decision-makers in formulating more reasonable policies to alleviate the conflicts between land utilization and ecological protection, and facilitate the realization of China′s ecological civilization construction goals. [ABSTRACT FROM AUTHOR]

• Soil nitrogen content and isotope values changed after cropland abandonment. • Mineralization is more active in karstic topsoil than in the deep soil layer. • The loss NO 3 – mainly originated from the cropland topsoil in present karst areas. • Land use change from cropland to forest can reduce soil N loss to aquatic system. A large amount of cropland in the Southwestern (SW) China karst area has been abandoned since the implementation of the Grain for Green project at the end of the last century, which significantly impacted the biogeochemistry cycle in soil. However, the effect of cropland abandonment on the soil nitrogen (N) cycle and the N loss process is still little understood. N content and isotope analysis were used to assess karst soil's N fate and explore the N loss process in SW China. Soil samples were collected from four land uses, cropland (CR), abandoned CR (AC), shrubland and grassland (SG), and secondary forest (SF), by seasonal in a typically mixed land-use karst catchment at six soil depths. The results showed that the average soil particulate organic N (PON) content increased from 1.58 ± 0.49 g kg−1 to 2.70 ± 1.82 g kg−1, whereas average dissolved nitrate (NO 3 –-N) content decreased from 10.77 ± 8.87 mg kg−1 to 1.72 ± 1.84 mg kg−1 during revegetation. There was a decreasing amount of PON and dissolved N (NH 4 +-N、NO 3 –-N、TDN) content from surface to the bottom of the soil profile and large variation mainly occurred in 0 – 30 cm in the soil profiles of four different land uses, which suggests N transformation mainly occurred in topsoil (<30 cm). Mineralization was the major nitrogen transformation process that affected PON content and δ15N-PON values. The highest δ15N-PON fractionation (-5.0‰) in the soil profiles of the four types of land use caused by mineralization was detected in SF. Variation of N content and isotope values in soil profiles after cropland abandonment suggested that the loss of NO 3 –-N in karst catchment mainly came from the topsoil of cropland. Overall, N loss from the topsoil of cropland should pay more attention, while cropland abandonment can effectively reduce the loss of dissolved N from the thin karst soil layer. [ABSTRACT FROM AUTHOR]

Soil moisture variations in space and time are critical in ecological, hydrological, pedological and environmental studies. This study used fractal analysis to detect the spatio-temporal variability of soil moisture on two contrasting land use hillslopes in the hilly area of Taihu Lake Basin of China. Surface (0–20 cm) soil moisture data from January 2013 to September 2015 (a total of 37 sampling days) were analyzed at 39 and 38 sites on the tea garden and forest hillslopes, respectively, with a spatial resolution of about 8 m. Results showed that the forest hillslope was significantly ( P < 0.05) wetter than the tea garden hillslope. The spatial mean soil moisture on both hillslopes had a significant negative linear correlation (R 2 = 0.753 for tea garden ( P < 0.05) and R 2 = 0.459 for forest ( P < 0.05)) with corresponding CV for 37 sampling dates. The fractal dimension (D) was found to be better than the nugget/sill ratio in describing the spatial dependence of soil moisture. The advantage of the D is that it does not require the modelling of the semivariogram since it can be calculated on the basis of the experimental semivariogram. Soil moisture on the forest hillslope showed stronger spatial dependence than that on the tea garden hillslope according to D. However, the soil moisture on both hillslopes showed similar temporal dependence and a low-to-moderate autocorrelation structure. In addition, the temporal variability of soil moisture content was spatially correlated on tea garden hillslope. If a location is temporally autocorrelated, the locations nearby tend also to be temporally autocorrelated. It would be possible to make more accurate moisture trend predictions for temporal autocorrelated locations with small D. These findings had important applications related to sampling design, simulation of soil water flow and agricultural water resources management. [ABSTRACT FROM AUTHOR]

Reduced streamflow is a major concern in the Haihe river basin, which supplies water for agriculture, industry and the growing population along the river. The upper Sang-kan (USK) river basin is the headwater of the Haihe river. To understand the drivers of streamflow change in this basin, effects of land use change and climate variability on temporal flow variability were studied using the Soil and Water Assessment Tool (SWAT). The calibration and validation results of the Scenario 0 ( S 0) model (with land use of 1986 and climate derived from 1979 to 1990) indicated that SWAT simulated monthly streamflow well. This was indicated by the Nash–Sutcliffe model efficiency ( NS ) and the Coefficient of Correlation ( r 2 ) for monthly flow, which were 0.89 and 0.91 for the calibration period (1981–1985) and 0.79 and 0.82 for the validation period (1986–1990), respectively. After calibration and validation of the SWAT model ( S 0), three different scenarios were simulated and compared in order to study the effects: Scenario 1 (land use of 2000 and climate during the 1979–1990 period, abbreviated as S 1), Scenario 2 (land use of 2012 and climate during the 1979–1990 period, abbreviated as S 2), and Scenario 3 (land use of 2012 and climate during the 2001–2012 period, abbreviated as S 3). By comparing the simulated hydrological results of S 0 vs. S 1 and S 2, and S 2 vs. S 3, and the annual changes in water use, it can be concluded that the recent perennial drought in the USK river has mainly been caused by human activities; warmer temperatures and less rainfall resulted in streamflow declining by 39.1%, while land use changes and the accompanied water use change for irrigation resulted in surface runoff increasing by 37.6% and streamflow increase between 2.2% and 3.9%, during the period of 1986–2012; increasing ground water and surface water usage for urbanization, industrialization, and reservoir constructions can be attributed from 63.1% to 64.8% of the perennial drought in USK river in recent years. The hydrological simulations provided a better understanding of streamflow changes in the USK basin. The study results can be helpful to maintain ecosystem services and sustainable water use in this region and in the Haihe River basin. [ABSTRACT FROM AUTHOR]

Riparian woodlands have recently been recognized as important carbon (C) storage regions with a considerable potential of sequestering C to mitigate global warming. Understanding soil organic carbon (SOC) storage in riparian woodland and the differences in SOC storage between riparian woodlands and other adjacent land types is important to effectively assess SOC storage in riparian woodlands and the influences of riparian land-use changes on SOC pool. Therefore, we thoroughly investigated C storage in the riparian woodlands along the Lijiang River watershed, located in a karst area in southwestern China. The goals of the study were to quantify the SOC density (SOCD) in the riparian woodland (0–20 cm depth of upper soil) [ N = 54, the plot area was 1130.88 ± 136.13 m 2 (mean value with standard deviation)]; to compare the differences in SOCD in the riparian woodland [bamboo-dominated ( N = 9) and non-bamboo-dominated woodlands ( N = 45)], the adjacent grasslands ( N = 13) and the farmlands [croplands ( N = 17) and orchards ( N = 17)]; and to assess the influence of soil texture, plant litter and soil root biomass on the SOCD of the riparian woodlands. The results showed that the average SOCD in the riparian woodlands of the Lijiang River watershed was 35.79 ± 9.51 t/ha. The SOCD in the non-bamboo-dominated woodland was 36.91 ± 9.63 t/ha, which was higher than that in the bamboo-dominated woodlands (29.86 ± 4.90 t/ha) by 7.05 t/ha (about 23.59%) ( p < 0.05) and was higher than that in the adjacent grasslands (27.77 ± 7.35 t/ha), croplands (28.93 ± 7.30 t/ha) and orchards (21.26 ± 8.20 t/ha) by 32.91%, 27.58% and 73.61%, respectively ( p < 0.01). However, the SOCD in the bamboo-dominated woodlands was only higher than that in the orchard by 8.60 t/ha (about 40.45%) ( p = 0.012). In the non-bamboo-dominated woodlands in the Lijiang riparian watershed, the SOCD showed a significant negative correlation with soil sand content ( r = − 0.69) and a significant positive correlation with the silt ( r = 0.59) and clay content ( r = 0.61) ( p < 0.01). The SOCD showed a significant positive correlation with plant litter ( r = 0.44) and soil root biomass ( r = 0.38) ( p < 0.05). Finally, the results indicate that the non-bamboo-dominated riparian woodland in the karst area stores more SOC compared with the adjacent grassland and farmland. However, converting riparian vegetation into bamboo woodland did not increase the accumulation of SOC and even caused some SOC loss in the Lijiang riparian area. [ABSTRACT FROM AUTHOR]

The impact of land use on the content of labile soil organic carbon (SOC) has been studied well. However, limited information is known about its effect on the recalcitrant SOC pool, which is a key proxy for long-term carbon sequestration. We investigated the impact of land use change on the distribution of labile and recalcitrant SOC fractions in soil profiles (0–30 cm) in the Jinchuan peatland, Northeast China, where native peatland (with peat soil) and forest (with mineral soil) are converted to paddy and cropland, respectively. Peat and mineral soil profile samples were collected from 10 sites in native and cultivated land. Total organic carbon (TOC) and KMnO 4 -oxidizable carbon (KOC) defined as the labile SOC fraction were measured in both peat and mineral soils. Fibre and lignin were also determined in peat samples. The mineral-associated organic carbon (MOC) and black carbon were examined as two recalcitrant SOC fractions. In peat soil profiles, the TOC and KOC contents increased with the increasing depth across all land uses. The conversion of peatland to paddy field can affect TOC content at each peat soil depth. The KOC content was lower in cultivated soils, indicating that cultivation decreased KOC. The KOC decrease was smaller than the TOC decrease, indicating that some recalcitrant SOC fractions were decomposed because of land use change. Unlike peat soil profiles, the TOC and KOC contents decreased with depth in mineral soil profiles across all land uses. The TOC and KOC contents in surface soil decreased remarkably after cultivation to cropland but were not affected in deep soil. Interestingly, recalcitrant SOC fractions, such as MOC, increased in mineral soil profile after cultivation but showed no change in peat soil profile. This study suggests that conversion of peatland to paddy can release the recalcitrant SOC fraction. In addition, conversion of cultivated forest to cropland decreased the TOC content but prolonged the long-term storage of some recalcitrant SOC fractions, such as MOC. [ABSTRACT FROM AUTHOR]

• The shear strength of soil-root system was measured by in-situ shear tests. • Shear strength of soil-root system changed significantly with land use type. • Shear strength was significantly affected by soil properties and root traits. • RSAD was the best parameter quantifying the effect of root trait on shear strength. Shear strength of soil-root system (SRSS) is one of the most useful dynamic properties for evaluating soil erodibility and structural stability. The adjustment of land use may strongly affect SRSS by altering soil properties and plant root system. Few studies have been conducted to investigate the effect of land use on SRSS in semi-arid region. This study was performed to quantify the variation in SRSS with five typical land use types (cropland, orchard, grassland, shrub land and woodland) and identify the related dominant contributing factors on the Loess Plateau where land use has changed greatly in the past several decades. In-situ shear tests with large shear box (25 × 25 × 10 cm) were conducted to measure shear stress-displacement curves. The strain energy calibrated to 15 % soil water content (SE c), peak shear stress (PSS) and the displacement of peak shear stress (DPS) calculated from the curves were used to reflect SRSS. The results showed that woodland had the maximum SE c (124.4 J m−2) and PSS (1048.6 kPa), whereas cropland had the minimum SE c (65.6 J m−2) and DPS (7.2 mm). Woodland, especially coniferous species and its mixed forest, might be the most suitable land use type for vegetation restoration on the Loess Plateau to enhance soil erodibility or structural stability. The variation in SRSS with land use was closely related to the changes in soil properties and root traits. PSS increased with penetration resistance, while it decreased with soil water content. DPS was positive correlated to root biomass and morphological traits. SE c was mainly affected by the direct and indirect effects of root surface area density, penetration resistance, soil organic matter content and aggregate stability. The results are helpful for understanding the mechanical mechanism of vegetation restored soils to mitigate erosion and optimizing land use type in semi-arid region. [ABSTRACT FROM AUTHOR]

[Display omitted] • The denitrification rate was higher in the abandoned land than shrubland. • Denitrification were lower in summer compared to winter in all land use types. • Soil environmental factors controlled over denitrification under different land use types. • The denitrifying genes was correlated with denitrification in each season separately. Despite the importance of nitrogen (N) cycling in terrestrial ecosystems, the underlying mechanisms of changes in the soil denitrification rate and microbial function under land use change remain unclear. Here we conducted a field experiment to explore soil denitrification rate, abundance and diversity of denitrifying genes (nirS , nirK , and nosZ) across summer and winter for three land use types (abandoned land, shrubland, and woodland) in subtropical China. The highest denitrification rate was observed in abandoned land (0.31 ± 0.03 mg m-2h−1) while the lowest was in woodland (0.24 ± 0.01 mg m-2h−1); however, denitrification enzyme activity was higher in both abandoned land (6.68 ± 0.18 ng g-1h−1) and woodland (6.35 ± 0.46 ng g-1h−1) than in shrubland (5.45 ± 0.24 ng g-1h−1). Both the denitrification rate and denitrification enzyme activity in all land use types were lower in summer than in winter. Notably, the alpha diversities of the denitrifying genes did not change significantly among the land use types. But the beta diversity of nirS significantly differed among the land use types, that of nirK did not significantly vary with seasons, and that of nosZ changed significantly with both different land use types and seasons. Overall, our findings reveal that soil moisture, soil organic carbon, and NO 3 –-N concentration predominantly regulate denitrification under different land use types, whereas soil moisture and denitrifying genes primarily control variations in denitrification between seasons, thereby providing novel insights into predicting the effects of land use change on N cycling and belowground microbial function. [ABSTRACT FROM AUTHOR]

[Display omitted] • With biological and non-biological elements through the maximum generalized entropy principle, a model was constructed to evaluate the stability of river ecosystem. • Comparison was made on stability and driving factors of sediment-starved clear and sediment-laden turbid river ecosystem. • Sediment-starved clear river ecosystem is affected under more factors than sediment-laden turbid river ecosystem. • Among the internal elements, turbidity has the greatest impact on the ecosystem stability of the two types of river ecosystems. • External background factors determine the direction of river ecosystem evolution. The stability of the river ecosystem can determine the health status of the river. And evolutionary driving forces of river ecosystem can reflect the useful information that the river basin disturbance response to the river, which can provide a theoretical basis for the protection and management of the river. The main goal of this study is to establish a river ecosystem stability evaluation model based on biological and non-biological parameters, and to quantify the effects of driving force, such as: human activities, hydrological situation, climatic factors and land utilization on river ecosystem evolution. In the southeastern part of China's Loess Plateau, we selected the mainstream of the Weihe River (hyper-concentration) and the tributaries (low-sediment-concentration) of the Weihe River at the northern foot of the Qinling Mountains. Results show that the evaluation model based on maximum generalized entropy principle (MGEP) is suitable for stability evaluation of different river ecosystems. The stability of hyper-concentration river ecosystem (3.371) is lower than that of low-sediment-concentration ecosystem (5.343). There are 5 key parameters affecting the ecosystem stability of hyper-concentration river while 8 of low-sediment-concentration river. Among the key parameters, turbidity has the greatest impact on the ecosystem stability of both types of rivers. Interestingly, the turbidity of hyper-concentration river is mainly affected by sediment content, while the turbidity of low-sediment-concentration river has a positive correlation with chlorophyll concentration. It's principally because the two river ecosystems are affected by different external driving forces. Hyper-concentration river ecosystem is mainly driven by land utilization, while low-sediment-concentration is primarily influenced by hydrological situation and climate factors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The point-to-line BLI-NDVI feature space model has high applicability with R2 = 92.0 %. • The rocky desertification city showed an overall weakening trend during 1985–2020. • The degree of rocky desertification in western Bijie city was higher than that in eastern parts. • The POP density and land use became the dominant factors in recent years. Significant differences exist in the dominant driving factors of rocky desertification evolution in varying temporal periods of mountainous karst areas in southwest China. However, previous studies were primarily conducted in specific periods. In this study, taking Bijie city (one of the areas most seriously affected by rocky desertification in southwest China) as an example, we analyzed the spatio-temporal evolution pattern of rocky desertification in Bijie city in recent 35 years by introducing the feature space model and the gravity centre model, and then clarified the dominant driving factors of rocky desertification in the study area in varying temporal periods based on GeoDetector. The findings were as follows: (1) the proposed point-line BLI-NDVI feature space model has higher applicability for rocky desertification monitoring with the overall inversion accuracy of 92.0 %; (2) during 1985–2020, there was an overall decreasing trend (weakening-aggravating-weakening) of the rocky desertification; (3) the spatial distributions and migration trajectory of gravity centre of rocky desertification indicated that the rocky desertification degree in the western parts was more severely than that in the eastern regions; (4) during 1985–2020, the land use and POP density have become the dominant factors of rocky desertification instead of vegetation coverage and temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Widespread soil erosion occurred in the hilly-gully region of the Loess Plateau. • Reclamation and deforestation in 1950–1970s caused severe soil erosion. • The increased vegetation coverage since the 1990s efficiently reduced soil erosion. • Restoring forest is more appropriated measure for soil erosion mitigation. • Convex micro-topography mitigate soil loss in sloping fields. Soil erosion strongly threatens the sustainability of natural ecosystems over the world, especially in the Loess Plateau in China, where has suffered severe soil erosion along with extensive land reclamation and deforestation from the 1950s to the 1970s. The large-scale vegetation restoration practices are supposed to be effective for reducing soil erosion, but the quantitative evaluation of soil erosion, particularly the response of land utilization types and vegetation coverage changes on the mitigation of soil degradation is still not well understood. Plutonium isotopes in soil cores collected from the forest, grassland slope, apple orchard, and cornfield in a typical watershed in the hilly-gully region of the Loess Plateau were analyzed to estimate the soil erosion rates in different land-use types. Widespread soil erosion at rates of 5.1–40.5 t/ha/yr. in this region in the past six decades was estimated. The influences of human activities in the past decades, type of land utilization, level of vegetation coverage, and terrain on the soil erosion in this region were discussed, and the accumulation of the eroded soil in the study sites was explored. Different types of land utilization showed diverse soil erosion rates (forest (slight) < grassland (light) < apple orchard ≈ cornfield (moderate)), indicating that natural vegetation rehabilitation, particularly restoring forest with high vegetation coverage is a practically effective conservation measure for soil erosion control; convex micro-topography on sloping fields is critical in alleviating soil loss by depositing eroded soil. [ABSTRACT FROM AUTHOR]

• Long-term environmental changes of Lake Baiyangdian are spatially heterogeneous. • Hydrological process and land use together lead to the spatial heterogeneities. • Major environmental transitions of the wetland occurred in the 1960 s and 1990 s. • Humulus pollen is a key indicator of anthropogenic impacts in populated wetland. Understanding long-term environmental changes and man-land interactions within wetlands is important for their ecological maintenance and restoration. However, there has been little focus on the spatial heterogeneity of environmental variations of wetlands, especially large agricultural wetlands, which hinders the development of targeted management programs for specific areas. We conducted a multi-proxy study of the sediments of a typical agricultural wetland, Lake Baiyangdian in North China, to assess the spatial heterogeneity of environmental changes over the past 70 years. The results reveal that the environmental changes in Lake Baiyangdian were spatially heterogeneous, mainly reflected by the response to hydrological variations before the 1970 s, and by changes in trophic level and land cover transitions since the 1990 s, which are strongly linked to changes in agricultural land use. Pollen and grain-size analyses revealed the large-scale spatial heterogeneity of changes in the sedimentary environment. Areas with greater openness, shallower water depths, and proximity to inflowing rivers were generally more sensitive to hydrological processes and provided regional records of environmental change. In contrast, populated areas far from inflows tended to capture more local changes related to anthropogenic impacts. Intensive agricultural activity has led to a continuous increase in nutrient enrichment and significant land cover transitions in Lake Baiyangdian, mainly the loss of natural wetland. Variations in Humulus pollen were a key indicator of these anthropogenic impacts. Hydrological processes and land use changes were together responsible for the spatial heterogeneity of the environmental variations in Lake Baiyangdian over the last 70 years, indicating the dominant role of human impacts on the spatio-temporal pattern of the evolution of this wetland ecosystem, and the complexity of its environmental management. [ABSTRACT FROM AUTHOR]

P is an essential and commonly limiting element for plants. P losses from agricultural production systems are known to contribute to accelerated eutrophication of natural waters. In this study, soil total phosphorus (STP) concentration and STP mass were estimated from a soil survey of a small watershed of the Dan River, China, after which the spatial heterogeneity of STP distribution and impacts of land-use types, elevation, slope and aspect on STP were assessed. A total of 190 sites were sampled, and 539 soil samples from a soil profile of 40 cm were collected by field sampling in a 100 m × 100 m grid. The results indicated that classical kriging could successfully interpolate STP concentration in the watershed. The STP concentration showed a downward trend with increasing soil depth. The STP variability in the three soil layers was moderate, and there were significant differences among soil layers (p < 0.01). Statistical analysis by ANOVA indicated that land use had a great impact on STP concentration, and the spatial variation of STP concentrations among the land use types was significant (p < 0.05). The STP mass of different land-use types followed the order of forestland > cropland > grassland. On average, the mean STP masses of forestland, cropland and grassland at a depth of 0–40 cm were 0.39, 0.35 and 0.28 kg/m 2 , respectively. The topographic factors of altitude and aspect exerted the greatest influence on STP concentration, and the STP concentration increased with decreasing altitude; however, STP concentration and slope showed no significant correlation. The soil bulk density also played a very important role in the assessment of STP mass. In conclusion, the soils in the source area of the middle Dan River would increase STP with conversions from cropland to forest. [ABSTRACT FROM AUTHOR]

• Lulao catchment (LLC) is a small, homogeneous watershed on Guizhou Plateau, SW China. • Farmland soil (FS) has higher IRM 300mT /SIRM due to stronger pedogenesis in LLC. • Grassland soil (GS) has low IRM 300mT /SIRM & higher HIRM in LLC where a reservoir lies. • Contribution of FS vs GS to reservoir sediment is inferred with sediment's magnetism. • Changes in erosion is inferred as FS is distant from the reservoir than GS. This paper demonstrates that land use could enhance spatial discrimination of soil magnetism in a homogeneous watershed, and such differences help infer alterations in sediment sources and erosion. One sediment core was sampled from a reservoir built in 1958 and fifteen soil profiles from its catchment on the southern Guizhou Plateau, SW China. The whole watershed was covered by yellow earth developed on limestone. Magnetic measurements and granulometric analysis were performed on the soils and sediments while TOC and TN analysis on two soil profiles and 137Cs analysis on the sediment core. Information of seven years' land-use was derived from remote sensing images. The farmland and grassland soils had different magnetic characteristics while the downwards distributions of TOC and C/N were similar in the two profiles. The grassland soils had higher HIRM, lower χ fd % and IRM 300mT /SIRM. The higher χ fd % and IRM 300mT /SIRM of the farmland soils suggested stronger pedogenesis under cultivation. The average HIRM, χ fd % and IRM 300mT /SIRM were 38 and 334 10-6 A m2 kg−1, 5.7 and 3.6%, and 0.91 and 0.66 for the farmland and grassland soils. The farmland soils were finer probably due to tillage. The reservoir has been closely surrounded mainly by the grassland whereas the farmland, embedded with patches of the grassland, has occurred in the terrains relatively distant from the reservoir. The sediments of 1958–1985 had lower HIRM (156 10-6 A m2 kg−1) and higher IRM 300mT /SIRM (0.79), indicating greater contributions of the remote farmland soils mixed with grassland soils and stronger erosion. HIRM increased (229 10-6 A m2 kg−1) and IRM 300mT /SIRM decreased (0.67) in the sediments of 1985–2019, implying decreased distant-soil contributions and relatively increased input of the grassland soil closely around the reservoir. Erosion thus weakened, as proven by the finer sediments. The declining erosion was mainly due to farmland shrinkage and grassland expansion. [ABSTRACT FROM AUTHOR]

• A field investigation of gully erosion was conducted in a 393 km2 area. • Larger ridge orientation angle and sunny slope were conducive to gully development. • Gully volume can be well predicted by a power function of gully area. • Soil loss caused by gully erosion occupied by 65% in northeast China. Gully erosion, one of the most damaging forms of land degradation, destroys farmlands and threatens grain and ecological stability. Approximately 295,000 gullies have formed in the Mollisols region of northeast China (NEC), while the actual severity of gully erosion remains unclear. This study aims to clarify gully morphology, factors influencing gully morphology, and contribution of gully erosion to soil loss through a 393 km2 field investigation in a typical and representative Mollisols region of NEC. There were 1048 gullies observed, with an average length, top width, depth and width-depth ratio of 522.32 m, 15.05 m, 2.77 m and 7.16, respectively. Over 70% of gullies had a length, top width and depth of 100–500 m, 3–20 m and 0.5–3 m, respectively. The three types of gullies, classified based on where the gully head developed (GF, farmland; GR, unpaved road; GW, woodland), had significantly distinct morphologies, with GW being broader and deeper and GF being longer. Notably, 56.2% of gullies are GF, accounted for 74.84% of the total gully area and 67.04% of the total gully volume (V). V of GF, GR and GW could be well explained by a power function of gully area (A). Gully density (gully length per unit area, GD, km km−2) and ground lacerative degree (gully area per unit area, GLD, km km−2) increased with slope gradient, and first increased and then decreased with slope length. Gully development was more favorable of sunny slope and a larger angle between gully and ridge orientation. The annual eroded soil from the gully was 1.86 times of that from the hillslope across the region during 2013–2018, contributing 65% of region eroded soil. This clearly identifies the severity of gully erosion and substantiates gully erosion risks to valuable mollisols and therefore food security. An urgent need exists to implement gully erosion control practices in this area. [ABSTRACT FROM AUTHOR]

We examined the impact of human changes in land use on the concentrations and stoichiometric relationships among soil carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in a Phragmites australis riparian wetland (Minjiang River estuary, China). We compared a natural (unaltered) wetland with five altered land uses: intertidal mudflat culture and vegetable, flower, fruit and rice cultivations. All these land uses decreased C, N and K soil concentrations relative to those in the P. australis wetland. The close relationship between total soil C and N concentrations, under all land uses, suggested that N was the most limiting nutrient in these wetlands. The lower N concentrations, despite the use of N fertilizers, indicated the difficulty of avoiding N limitation in the agricultural land. Croplands, except rice cultivation, had lower soil N:P ratios than the original P. australis wetland, consistent with the tendency of favoring species adapted to high rates of growth (low N:P ratio). The release of soil C was less and the soil C:N and C:P ratios higher in the natural P. australis riparian wetland than in the croplands, whereas C storage was more similar. The levels of soil C storage were generally opposite to those of C release, indicating that C release by respiration was the most important factor controlling C storage. Cropland soil management promotes faster nutrient and C cycles and changes in soil nutrient stoichiometry. These impacts can further hinder the regeneration of natural vegetation by nutrient imbalances and increase C-cycling and C emissions. [ABSTRACT FROM AUTHOR]

Rainfall and land use conversion are important factors influencing soil erosion. Differing from the stationary land use type, land use conversion is a process of dynamic change usually spanning several decades. Soil erosion modeling using historic land use data offers an opportunity to study the impacts of actual land use conversion on soil erosion. However, rainfall has been taken into account only in a few studies because its spatio-temporal distribution often varies greatly over a long period of time. In this article, the erosivity index was used to quantify the erosive force of rainfall. Based on entropy theory, erosivity distribution of study area during the 1988 to 2013 period was analyzed. Two extreme zones, Zone I and Zone II, with highest and lowest annual erosivity, respectively, were identified. The intensity of soil erosion among land use types are: farmland > orchard > grass/open forest > shrub > forest. Zone I has severer soil erosion than Zone II. The effectiveness of land use conversion for reducing soil erosion varies between different erosivity zones. Farmland–forest conversion is considered as the first choice to reduce soil erosion when land use conversion is implemented. The conversions of farmland–grassland and farmland–open forest can be used as important supplements to conversion of farmland–forest in low erosivity zone of the study area, although they do not perform well under higher erosivity situation. [ABSTRACT FROM AUTHOR]

Soil erosion has been a major environmental issue in China. However, the overall rate and the variability in runoff and soil loss of different regions and land uses in China have not been reported in the literature. In this study, an extensive database of runoff plots in China was compiled. Runoff and soil loss rates of sheet and rill erosion under natural conditions based on plot studies, are reviewed. The history of plot studies in China is briefly introduced, and basic information, such as the geographic distribution of soil erosion monitoring sites, the distribution of slope length and the slope gradient of runoff plots, is described. The runoff and soil loss rates of five water erosion regions in China were analyzed in terms of the main land use types. The soil loss rate was 30.87–107.44 t ha − 1 a − 1 on fallow land and 7.65–49.38 t ha − 1 a − 1 on farmland under conventional tillage. The land use types with permanent cover experienced the lowest soil loss rates, which were 0–1.89, 0.28–8.06 and 3.98–1.57 t ha − 1 a − 1 for forest, shrub and grassland, respectively. In China, the regional differences in the soil loss rate were mainly observed on fallow land and farmland, whereas almost no differences were observed on forest, shrub and grasslands. The soil loss rates of forest, shrub and grasslands showed no significant differences worldwide. However, the soil loss rates of farmland with conventional tillage in northwest and southwest China were much higher than in most other countries. This indicated that farmlands in China are still suffering from a very serious erosion problem that requires additional future attention. This study provided a broad assessment of sheet and rill erosion for prioritizing problems and selecting the appropriate erosion control practices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wet-dry cycles reduced SAS at high flooding intensity sites in the riparian zone. • Wet-dry cycles enhanced soil respiration in the riparian zone. • Wet-dry cycles weakened the carbon sequestration of soil aggregates in the riparian zone. Increasing the frequency and magnitude of wet-dry cycles can fundamentally affect soil carbon (C) turnover. However, the response of soil respiration to intense wet-dry cycles in the riparian zone is unclear. Hence, this study aimed to identify whether soil respiration and soil aggregates in different land use types were affected by different flooding intensities in the riparian zone of the Three Gorges Reservoir, China, and determine the responses of soil organic carbon (SOC) sequestration by soil aggregates to wet-dry cycles in the riparian zone. At the Wuyangwan of the Pengxi River, a tributary of the Yangtze River in the Three Gorges Reservoir, soil respiration and soil aggregates were investigated at different elevations of the riparian zone with representative land use types, namely a cornfield (173C) and a paddy field (173P), both at an elevation of 173 m above sea level, and two paddy fields, 168 m and 163 m above sea level (168P and 163P). The results showed that soil aggregate stability increased (e.g., the mean weight diameter increased by 38% and 18% for 173C and 173P, respectively) in the low flooding intensity sites and decreased (e.g., the mean weight diameter decreased by 44% and 33% for 168P and 163P, respectively) in strong flooding intensity sites after four wet-dry cycles in the riparian zone of the Three Gorges Reservoir. Moreover, the wet-dry cycles increased soil respiration (i.e., the soil respiration increased by 36%, 218%, 129%, and 31% for 173C, 173P, 168P, and 163P, respectively). In addition, soil aggregate stability had a direct negative effect on soil respiration (namely, the mitigation of CO 2 emissions), and the negative effect weakened after four intense wet-dry cycles (pathway coefficient was −0.76 in 2014 and −0.28 in 2018). Thus, the carbon sequestration of soil aggregates was weakened in the riparian zone. The size of the soil aggregate fractions and their organic carbon contents directly or indirectly affected soil respiration. Most notably, the proportion of microaggregates and their associated nitrogen and organic carbon contents strongly influenced soil respiration. Finally, from the perspective of maintaining soil aggregate stability and SOC sequestration, we suggest that agricultural activities should be prohibited in areas with high flooding intensity in the riparian zones. [ABSTRACT FROM AUTHOR]

• 91.72% of the soil in Xunwu County exhibited an acidification trend over 35 years. • Main conversion modes were cropland and forest changed to garden and other land. • Soil pH variability and land use type correlated in 1984 and 2018 (P < 0.01). • Land use change altered the influence of factors on soil pH variability. Abnormal changes in soil acidity and alkalinity impact regional food security and sustainable development of terrestrial ecosystems, especially under land use change. The regulation of soil acidity and alkalinity requires a clear understanding of soil pH variability and its influencing factors under regional land use change. This study explored the patterns of soil pH variability under land use change between 1984 and 2018 in a red soil hilly region (Xunwu County, Jiangxi Province) in southern China. We identified the key factors influencing regional spatiotemporal variability in soil pH and analyzed the response of soil pH variability to land use change. The results showed that the mean pH values of surface soil samples in 1984 (n = 595) and 2018 (n = 580) were 5.35 and 5.05, respectively. The soil pH change between the two periods ranged from −0.91 to 0.32, with a mean value of −0.30. In total, 91.72% of the study area showed an acidification trend from 1984 to 2018. The spatiotemporal variability in soil pH was influenced by elevation, slope, distance to rivers, changes in distance to roads, and changes in the nitrogen fertilizer application rate. The main land use conversion modes were cropland and forest transferred to garden and other land. The soil pH decreased in 15 of 16 conversion modes of cropland land, garden, forest, and other land, whereas a pH increase of 0.32 occurred under conversion from cropland to garden. Changes in distance to roads, changes in the nitrogen fertilizer application rate, and slope played a dominant role in soil pH variability under land use change. This study provides fundamental data for the formulation of soil acidity and alkalinity control measures, which in turn contributes to regional improvement of agricultural production stability and sustainable development. [ABSTRACT FROM AUTHOR]

• Driving factors of SOC and total N were explored in 28 lucerne fields. • The SOC and total N were mainly explained by soil resources. • Soil P, moisture, and altitude were the key factors affecting SOC and total N. • Plant species diversity positively affected SOC and total N contents. • A strong interaction effect was observed among topography, vegetation and soil on SOC. Lucerne (Medicago sativa L.) is one of the most successfully introduced species for revegetation on the Loess Plateau of China and provides important ecosystem services. However, the driving mechanism of soil organic carbon (SOC) and total nitrogen (TN) in lucerne grasslands remains unclear. This study explored the controlling factors of SOC and TN in lucerne grasslands in the semiarid Loess Plateau. A total of 112 quadrats were employed in 28 lucerne fields. Vegetation characteristics, topographic factors, and soil properties at a 0–20 cm depth were measured in each quadrat. The SOC and TN contents increased with altitude and showed positive correlations with species richness, aboveground biomass of native plants, soil moisture, soil inorganic nitrogen, total soil phosphorus (P), and C:P and N:P ratios. Variations in SOC and TN contents were mainly attributed to soil resources, followed by the interaction of topography, vegetation and soil. Soil P, soil moisture, altitude, and native plant species were the main factors controlling SOC and TN contents in these lucerne grasslands. Results suggest that specific abiotic (soil P and moisture) and biotic (plant species diversity) factors controlled SOC and TN in semiarid lucerne grasslands. These factors should be included in SOC and TN evaluation models to predict the future terrestrial ecosystem carbon and nitrogen dynamics. [ABSTRACT FROM AUTHOR]

• Pollen records reconstruct the late Holocene land use and vegetation dynamics. • Human land use has impact on the regional vegetation and landscape since 50 CE. • A large-scale transformation of the landscape occurred since 750 CE. • Late Holocene vegetation changes were mainly controlled by temperature. Knowledge of the past interactions between climate and human land use is essential for understanding the possible future relationships between global change and human societies. In this study, we used pollen and other multi-proxy analyses of the sediments from Xingyun Lake in central Yunnan Plateau to reconstruct the history of land use and ecosystem dynamics during the last 3,200 years. The pollen results indicate that the vegetation became more open gradually and many secondary forests began to grow during the last 100 years. During the Medieval Climatic Anomaly (MCA), the vegetation is dominated by broad-leaved trees, while during the Little Ice Age (LIA) the broad-leaved trees declined but Picea/Abies expanded. Human land use has impacted on the regional vegetation and landscape since 50 CE; large-scale human land use occurred after 750 CE. The sediment accumulation rate (SAR), pollen record, and 14C age offsets reveal that soil erosion is well correlated with human activity and changes in vegetation cover. Before 750 CE, soil erosion was probably limited, but after 750 CE it increased drastically as a result of human activity, and then decreased during the last 100 years. According to the results of the redundancy analysis (RDA), we conclude that climate had an important impact on the regional vegetation, and the late Holocene vegetation changes of Xingyun Lake catchment were mainly influenced by temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil C, N and P stoichiometric ratios were influenced by land use types under different erosion conditions. • Soil C, N and P stoichiometry changed more significant under SE condition. • Higher P stocks and lower C:N:P stoichiometric ratios were detected in PD and UL than in WL. • Land-use type affected C, N and P stoichiometry mainly by changing soil porosity and texture. Irrational land-use can accelerate soil erosion by deteriorating soil structure and depleting soil nutrients, especially profoundly alter soil organic carbon (C), total nitrogen (N), total phosphorus (P) contents and stocks. However, it remains unknown how soil C, N, P stoichiometry patterns are affected by land-use type and soil erosion. This study was carried out to examine the soil C:N:P stoichiometry patterns in woodland (WL), upland (UL), and paddy (PD) at soil depths of 0–10, 10–20, and 20–30 cm under collapsed gully erosion (CGE) and sheet erosion (SE) conditions in lateritic red soil region. Compared to WL, C content and stock decreased by 19.1–31.9 g kg−1 and 12.8–31.7 Mg ha−1, but P content and stock increased by 4.9–7.4 g kg−1 and 6.7–9.9 Mg ha−1 in UL soil at 0–30 cm, resulting in a decrease in C:N, C:P and N:P ratios by 8.6–14.8, 23.0–28.6 and 0.7–1.0, respectively. In addition, N, P contents and stocks increased by −0.04–1.8 g kg−1, 4.1–10.5 g kg−1 and 1.8–1.1 Mg ha−1, 7.0–8.2 Mg ha−1 in PD soil at 0–30 cm, resulting in a decrease in the ratio of C:N, C:P and N:P by 8.1–10.6, 20.7–26.0 and 0.6–0.8, respectively. Furthermore, C, N, P contents, stocks and C:N ratio in UL and PD soils were more significant under SE than CGE condition with, while it was opposite trend in WL at 0–30 cm depth. Soil C, N, P contents and stocks significantly decreased with soil depth, while no significant changes were detected on their stoichiometric ratio. Soil porosity and texture had significant contribution to C, N and P stoichiometry by PCA and RDA analysis. Our results demonstrate that the intensive agricultural practices changing soil porosity and texture under SE condition led to more pronounced differences of soil C, N, P and their stoichiometric ratios in lateritic red soil region. [ABSTRACT FROM AUTHOR]

• NPS TP township loads for different cultivated land use-patterns were simulated. • The average GGE TP load was the highest, and the GES and GOCS loads were similar. • The NPS TP load with different cultivated land-use patterns was heterogeneous. • The correlations varied between the cultivated land uses and NPS TP loads. • Cultivated land-use classification can clarify the NPS pollution driving mechanism. Non-point source (NPS) pollution caused by unsustainable cultivated land use is becoming more severe. It is therefore critical to understand the complex relationships between cultivated land use forms and NPS pollutant loads from the perspective of integrated cultivated land use. This study used the cultivated land use pattern to integration represent the various forms of cultivated land use, and constructed a model to estimate NPS pollutant outputs at an administrative-region scale. This model was used to quantitatively simulate the NPS total phosphorus (TP) loads of townships with different cultivated land-use patterns in Chaohu Lake Basin, China, since 2000. The relationships between the TP loads and the different cultivated land use patterns were then assessed to clarify the corresponding function mechanisms and provide scientific support for effective NPS pollution controls. The cultivated land-use patterns of the townships in Chaohu Lake Basin were classified as suburban compound operations (SC); grain and economical crop scale operations (GES); grain and economical crop extensive operations (GEE); and grain, oil, and cotton scale operations (GOCS). The TP loads of townships with various cultivated land-use patterns were significantly different. The average TP load of GEE pattern townships was the highest (5.39 kg ha−1a−1), which was 1.85 times the lowest value of the SC pattern townships. The TP loads of GES and GOCS pattern were similar (3.52 kg ha−1a−1 and 3.19 kg ha−1a−1, respectively). The heterogeneous NPS TP loads are due to the face that cultivated land-use forms exhibit different marginal inhibition/promotion effects on NPS pollutant outputs with different patterns. Different correlations and significances were observed between various cultivated land-use form factors and NPS TP loads with different patterns. Therefore, accurate classifications and recognition of cultivated land-use patterns can be utilized to clarify the function mechanism between cultivated land use and NPS pollutant loads. [ABSTRACT FROM AUTHOR]

• Vegetation was the main landuse change type, with an increase of 46.65% in 1964–2018. • Connectivity index (IC) was spatially variable and lower in the main gully. • IC was impacted by re-vegetation, terrace, and dam land in descending order. • Connectivity variations were quantitatively related to sediment yield reduction. The spatial distribution of landscape pattern in catchments has a great impact on the potential sediment detachment and transport capacity. In this study, a sediment connectivity model was applied to evaluate the effect of the spatial distribution of landscape pattern on the sediment transfer in a typical catchment on the Loess Plateau in China based on land use and topography data in 1964, 2004, and 2018. Thereupon, the impacts of changes in different land use types on sediment connectivity and those of sediment connectivity changes on sediment yield reduction in the catchment were quantified. The results showed that (i) grassland and slope farmland were the main land use types in the catchment, and a decrease of the slope farmland area and an increase of the vegetation coverage occurred from 1964 to 2018; (ii) compared with 1964, most parts of the catchment in 2004 and 2018 had an overall lower connectivity index (IC); (iii) the distribution of sediment connectivity presented obvious spatial variability. The hill slopes and tributary gullies tended to be relatively well connected, and the main gully was highly disconnected. Scenario simulations showed that the potential sediment reduction effect was 20%−45% for vegetation, and <10% for terraces or dam lands in 1964, 2004, and 2018. The effect of impounding sediment by check dams was not included in IC calculation in this study, and it was found that the sediment impounded by these dams accounted for about 16% of sediment discharge reduction during 1995–2004 and 1% during 2005–2018. The IC reduction was responsible for 84% of the decrease of sediment discharge during 1995–2004 and 99% during 2005–2018, reflecting that vegetation restoration and terrace construction on slopes has become the main drivers for reducing IC value and sediment yield. [ABSTRACT FROM AUTHOR]

• Dynamics of vegetation coverage and its response to LUCC were explored. • The influence of LUCC on NPP in Yangtze River basin was assessed. • The relative contribution of LUCC and climate change was distinguished. • The combination effect of LUCC and climate change resulted in total NPP increase. Land use and land cover change (LUCC) will directly affect the types, structures and functions of ecosystems, and then have important impact on vegetation net primary productivity (NPP). The evaluation of the spatio-temporal dynamic changes of LUCC and regional NPP, and assessing the impact of LUCC on NPP can facilitate the corresponding management of different environmental types of regions and provide scientific guidance for scientific development of ecological resources, and better restore and control the ecological environment, thus promoting rapid economic development. Using MODIS normalized difference vegetation index (NDVI) data and meteorological data from 2001 to 2018, combined with Carnegie-Ames-Stanford model (CASA), the regional NPP was estimated, and the influence of LUCC on NPP in Yangtze River basin from 2001 to 2018 and its causes were analyzed. The results showed that the area with a land cover and land use change account for 10.98% of the total study area in the past 18 years, and the most important change is the transformation from grassland to forest and grassland to crop/natural vegetation mosaic (NVM). Forests, wetlands, crop/natural vegetation mosaic, low vegetation cover (LVC) land, urban, and water bodies are growing. The forest land area increased the most and that of grassland decreased the most. Total NPP has increased by 53887.51GgC in the past 18 years, which was due to the combination effect of LUCC change and climate change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grass land was the dominant land use type and its area increased during 1980–2015. • Decrease of bare land provides the basis for the expansion of other land use types. • High conversion rate and intensity of LUCC were found in TSMs from 2000 to 2015. • The aggregation and fragmentation of overall landscape pattern increased in TSMs. • Accelerated glacier melting promotes the progress of LUCC in TSMs. During the past decades, land use/land cover change (LUCC) has occurred in the glacial affected areas at unpredictable rates driven by natural and human factors. Monitoring and identifying the spatial and temporal land cover changes and driving forces in this unique type of region provides a scientific basis for understanding the changing process of the Earth's surface, helping to reveal the impact of climate change and human activities on LUCC. In this study, the Tianshan Mountains (TSMs), which are located in the hinterland of Eurasia, were selected to investigate the LUCC of its typical glacial affected areas that have significant regional particularities. LUCC processes in the TSMs in China over the past 35 years were analyzed using a dynamic change model, a landscape pattern index, a centroid transfer model, and geoinformation Tupu based on the land use data of 1980, 1990, 2000, and 2015. The results show that the areas of cultivated and built-up lands immensely increased by 45.87% and 187.10%, respectively. Correspondingly, the areas of bare land and ice and snow cover decreased by 26.76% and 37.93%, respectively. The land use change in the TSMs was characterized by different stages, and high conversion rates and intensities were obtained from 2000 to 2015. The landscape change was mainly reflected in the significant increase in the number of patches and the simplification and regularization of patch shapes. The spatial connectivity of different land use types also increased. The temperature and precipitation in the region showed increasing trends, and the melting rate of ice and snow cover significantly accelerated. This study can help achieve a dynamic LUCC model to investigate the interacting influences of climate change and human activities in glacial affected areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Olsen-P in 6-m deep profiles was determined in Loess Plateau farmland and orchards. • Farmland-to-orchard conversion affected Olsen-P at 0–40 cm but not at 40–600 cm. • Soil Olsen-P at 71.2 kg P kg−1 was the change point against leaching of P. • Olsen-P was regulated by P fertilization at 1 m and by roots at 1–6 m. Data on the dynamics of Olsen-P in deep soil profiles are crucial for improving P use efficiency but remain scarce worldwide. Hence, we sampled sixty 6-m-deep soil profiles from farmland and in 8-yr, 17-yr, and 25-yr-old apple orchards on China's Loess Plateau, and aimed to investigate the vertical distribution of soil Olsen-P following the farmland-to apple orchard conversion. Land-use change from farmland to apple orchard significantly affected Olsen-P at 0–40 cm soil, with the concentration generally increasing with age of apple orchard. By contrast, Olsen-P at 40–600 cm was not significantly different among the cropping systems. In both farmland and apple orchards, the concentration of Olsen-P decreased at 40–100 cm, compared with that in the 0–40 cm layer, increased with depth from 100 to 400 cm and then stabilized from 400 to 600 cm. The highest accumulation of residual soil Olsen-P in the 6-m profile (RSP 0−600) was in the 25-yr orchard, followed by the 17-yr and 8-yr orchards, with the lowest accumulation in farmland. The differences in RSP 0−600 cm were primarily associated with RSP 0−100 cm , which was significantly positively related to the accumulative application of P fertilizer. The change point in soil Olsen-P against P leaching was 71.2 mg kg−1, but in farmland and 8-yr, 17-yr, and 25-yr apple orchards, the averaged-depth contents of Olsen-P were all below the critical value, indicating no P leaching risk. Regression analysis revealed that the vertical distribution of soil Olsen-P was regulated by P fertilization at 0–100 cm and by crop roots at 100–600 cm, irrespective of cropping system. The insights gained on Olsen-P accumulation and migration within deep soil profiles after the farmland-to-apple orchard conversion can help to optimize land use and P fertilization management in major apple-producing countries with burgeoning growth in apple production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temporal patterns of sediment OC burial over the past ~100 years were studied. • Increasing OCAR during 1880–1980 was favored by land use promoting P input. • Decreasing OCAR since 1980 was associated with enhanced OM decomposition and OC mineralization. • OC pool may be mediated under projected climate warming scenarios for deep lakes. Inland waterbodies play an important role in the global carbon cycle, acting both as carbon sources with organic carbon (OC) mineralization and as sinks with OC burial in sediments. Under recent impacts of global warming, anthropogenic land-use change and nutrient supply, however, there is a limited knowledge regarding OC dynamics in sediments of large, deep lakes especially in subtropical alpine regions. Here, we studied the patterns of OC burial and the potential regulating factors using multiple sedimentary proxies and observational records in Lugu Lake (southwest China) over the past ~100 years. Comparisons of 15 sediment cores in different areas of the lake reveal similar temporal trends in OC content and other sediment parameters, indicating coherent patterns of whole-lake sedimentary environmental change dominated by watershed human perturbation. Based on C/N ratios and δ13C org analyses, the sediment OC has primarily been autochthonous in source. OC accumulation rates (OCAR) increased during 1880–1980, from ~14 to 43 g C m−2 yr−1 in a central core (LGS), mainly resulting from elevated primary production under increased phosphorus input and soil erosion. Subsequently, OCAR decreased considerably to ~15 g C m−2 yr−1, although the phosphorus supply and lake primary productivity remained high. We infer the OCAR decline likely resulted from increased organic matter decomposition and OC mineralization in the water column because of climate warming and lake-water thermal stratification. This phenomenon might mask the positive contribution of primary production to OC burial. Our findings suggest that the commonly observed synergistically positive effects of warming and eutrophication on sediment OC burial may be impaired in deep lakes, which needs further investigations across ecological, climatic and land-use gradients. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interactive effects of soil erosion and land use on SOC were studied. • Soil erosion rates were higher in orchard land relative to farmland. • The direct impact of soil erosion accounts for 1.5% of SOC variability in soil surface. • The direct or indirect effects of land use accounts for 89.0% for SOC variability in deeper soil. Changes in land use can result in soil erosion and the loss of soil organic carbon (SOC). However, the individual contribution of different land use types on SOC variability as well as the combined impacts of land use and soil erosion are still unclear. The aims of the present study were to: (1) evaluate soil erosion and SOC contents under different land use types, (2) identify the influences of soil depth and land use on SOC content, and (3) determine the contribution of land use and soil erosion on SOC variability. We assessed the SOC and total soil nitrogen (TSN) contents under three types of land use in the dry-hot valley in southern China. Caesium-137 (137Cs) and excess lead-210 (210Pb ex) contents were also measured to determine soil-erosion rates. Land use was found to significantly affect soil erosion, and erosion rates were higher in orchard land (OL) relative to farmland (FL), which is in contrast with previous study results. SOC and TSN contents varied significantly between the three land use types, with highest values in forest land (FRL) and lowest values in OL. SOC was found to decrease with decreasing soil depth; the highest rate of reduction occurred in the reference site (RS), followed by FRL and FL. The interaction between soil erosion and land use significantly impacted SOC in the soil surface layer (0–12 cm); the direct impact of soil erosion accounted for 1.5% of the SOC variability, and the direct or indirect effects of land use accounted for the remainder of the variability. SOC content in deep soil was mainly affected by factors related to land uses (89.0%). This quantitative study furthers our understanding on the interactive mechanisms of land use and soil erosion on changes in soil organic carbon. [ABSTRACT FROM AUTHOR]

• Soil particles had the similar parabolic relationships with soil aggregate stability. • Nitrate nitrogen plays an important role in surface soil aggregate stability. • Abandoned apple orchards can improve soil aggregate stability through a short time. Soil aggregate stability is a feasible and effective factor to understand the complex interactions between physicochemical properties and soil structure. To reveal the distributions of soil aggregate stability and its influential factors following land use change from apple orchards abandonment and development in the Nangou watershed of the Loess Plateau, China, this study selected five ages of apple orchards and their planting years were 1 year, 3 years, 6 years, 8 years and 10 years, one 15-year grassland developed from an apple orchard, one 15- year grassland developed from farmland, one natural grassland and one 15-year locust. Results showed that restored vegetation had better soil aggregate stability, soil organic carbon (SOC), and nitrogen (N) than apple orchards, and the composition of soil particles with the best aggregate stability was clay 6%, silt 8%, and sand 86%. At a 0–10 cm soil depth, soil aggregate stability had a significant positive correlation with SOC and soil total nitrogen (STN), and a negative correlation with NO 3 − and NH 4 +. In addition, vegetation diversity and coverage only affected the soil aggregate stability of the 0–10 cm soil depth; however, soil pH, bulk density, and soil aggregate-associated inorganic nitrogen were the main influential factors that drove the soil aggregate stability of the 0–30 cm soil depth. Further research discovered that macro-aggregate associated NO 3 − and micro-aggregate associated NH 4 + may be the key factors affecting the soil aggregate stability. Therefore, it is essential to further explore the effect of soil aggregate-associated inorganic nitrogen on soil aggregate stability. [ABSTRACT FROM AUTHOR]

• The number of organic phosphate-solubilizing bacteria (PSB) increased with soil TP. • The number of phosphate-solubilizing fungi (PSF) increased with soil carbon content. • The ability to solubilize phosphate was organic PSB > PSF > inorganic PSB. • The organic PSB was the best bacterial group to solubilize phosphate. Some soil bacteria and fungi are known to solubilize phosphates and play an important role in supplying phosphorus (P) to plants. In this study, we characterized the phosphate-solubilizing bacteria and fungi as well as P availability in latosols from southern China under different land use practices. Three different latosols (i.e., red soil, lateritic red soil and laterite red soil), each with four different land uses (i.e., agricultural land, grass land, forest land and orchard land), from Guangdong Province, China, were chosen to determine the amounts of phosphate-solubilizing bacteria (PSB) and phosphate-solubilizing fungi (PSF) and their phosphate solubilizing abilities. Our results show that the amount of available P (AP) increased with the amount of PSB favored in solubilizing organic P (or PSBop), while the amount of PSF increased with the content of soil organic carbon (SOC). The average rates of phosphate solubilization were 28.23% for PSBop, 6.97% for PSF, and 0.16% for PSBip (PSB favored in solubilizing inorganic P). An increase in soil pH decreased the ability of PSB to solubilize phosphate in latosols. This ability occurred in the following order: PSBop > PSF > PSBip. No significant difference in the amount of PSF was observed among the four different land uses for the lateritic red soil and laterite red soil, whereas a profound significant difference was found for the red soil, with the highest number of PSF in the grass land. Reasonable linear correlations between the PSB and the AP and between the PSF and the SOC were obtained and could provide a good reference to characterize soil PSB and PSF. Additionally, PSBop was the best bacterial species to solubilize phosphate in the latosols. [ABSTRACT FROM AUTHOR]

• The increase rate of active C was higher than those of intermediate and passive C. • Increased proportion of active C with the forest age led SOC to become more labile. • The increase of C:N ratio verified that SOC becomes more labile after reforestation. Land use changes have a great impact on carbon (C) cycling of terrestrial ecosystems by changing both the C inputs and mineralization rates. It not only results in variations of SOC stocks, but that the SOC properties could also change after vegetation conversions. In this study, we collected soil samples in a series of forests converted from croplands at different times in Southeast China. The effects of the reforestation on SOC pools and stabilities were investigated based on information of SOC contents, SOC fractions (active, intermediate and passive C) and C:N ratios. The organic carbon (OC) contents of the bulk soil and soil fractions increased with the forest ages in both topsoils (0–10 cm) and subsoils (40–50 cm). The increase rates of the active C were higher than those of the intermediate and passive C. As a result, the proportion of the active C increased with the forest ages, which would result in an increase of SOC instabilities. This was confirmed by the observation that the C:N ratio of the bulk soil increased with the forest ages. Our results implied that the C sink potential of the forest soil is to a large extent determined by the forest age. [ABSTRACT FROM AUTHOR]

• Multiple tracers were employed to identify the sources of eroded OM in sediments. • Gully banks were the main contributing sources to eroded bulk OM at multiple scales. • Sediment bulk OM mainly sourced from the region with light erosion intensity. • Biological production of OM impacted on the dynamics of water-extractable OM. Erosion is a fundamental phenomenon that governs the biogeochemical cycle of carbon (C) in the Earth system. Understanding the fate of eroded C at the watershed scale thus provides essential guidance for balancing the C budget and evaluating soil management strategies. In this study, we collected a total of 229 topsoils of source materials [land use types (forests, grassland, cropland, orchard, and fallow) and gully bank] and a total of 56 surface sediment samples [main river channel (18) and three tributaries (38) with different erosion intensity]. Multiple tracers (C and nitrogen (N) isotopes, molecular n-alkane biomarker, and spectroscopic indices) applied widely were then analyzed to determine relative source contributions to eroded organic matter (OM) (including bulk OM and water-extractable OM) in sediments at a broader watershed on the Loess Plateau of China. The results from an isotopic mixing model analysis showed that gully bank was the primary contributor of bulk OM in sediments, accounting for mean probability estimate (MPE) 55.3%, followed by "grassland" (MPE 21.0%), "cropland" (MPE 14.4%), and "forests" (MPE 9.3%). The contributions of grassland and cropland showed an increasing trend from upstream to downstream sections of the studied watershed. The contribution of forests was found higher in upstream than those of midstream and downstream. Along with previous evidences, our results show that erosion intensity mainly affects the proportion of C source, where gully bank was found as the highest contributor in three associated catchments, especially in region with light erosion intensity. We further demonstrated that the sediment bulk OM deposited was mainly derived from the region with light erosion intensity at the broader watershed scale. Moreover, results of n-alkane ratios and spectroscopic indices also implied that biological production of OM other than terrestrial sources (i.e., soil OM) might play a critical role in source contribution of water-extractable OM in sediments of main river channel. [ABSTRACT FROM AUTHOR]

• Soil surface roughness differed greatly between different land uses and plant species. • RR was affected by near soil surface characteristics after vegetation restoration. • RR was dominated by tillage operations for land uses with tillage operations. Soil surface roughness (SSR) significantly influences hydrological and erosion processes under different conditions. Land use and its adjustment may greatly influence SSR via altering near soil surface characteristics and tillage operations, but few studies have been performed to quantify their effects on soil surface roughness. This study was conducted to investigate the variation in soil surface roughness under different land use types, and identify the main influencing factors contributing to these changes in a small watershed on the Loess Plateau, China. Eighteen sites were selected from five typical land use types (cropland, grassland, shrub land, orchard, and woodland) to measure random roughness (RR) by a photogrammetric method. The results showed that random roughness was greatly affected by land use types, plant species, and tillage operations. The mean RR under different land use types ranged from 9.47 to 10.06 mm. Woodland had the maximum RR , followed by cropland, shrub land, orchard, and grassland. For a given land use type, RR differed significantly between different plant species. The variation in random roughness was greatly influenced by the changes in near soil surface characteristics and tillage operations induced by land use adjustment. For the testing sites without tillage operations, RR increased linearly with soil median grain size, sand content, organic matter content, plant litter coverage, litter thickness, and litter density, while it decreased linearly with soil cohesion, silt content, and clay content. For the testing sites with tillage operations, RR was dominated by tillage operations. These results are helpful to understand the potential effects of vegetation restoration on hydrological and erosion processes on hillslopes in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]