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• Soil erosion is estimated at 2.32 Mg/ha/yr across all LULC classes in the US. • Croplands are responsible for 44% of soil erosion on 17% of US land. • Cultivated and other vegetated lands contribute to 90% of soil erosion. • The highest soil erosion rates are seen in corn, soybean, and wheat lands. • Future urban and cropland expansion will increase soil erosion rates in the US. Brought on by anthropogenic actions, accelerated soil erosion inflicts extreme changes in terrestrial and aquatic ecosystems. These field-scale (30 m) changes have neither been fully surveyed in the present, nor predicted for a probable future. Water-driven soil erosion (i.e., sheet and rill erosion) rates across the contiguous United States were estimated for the present, and then predicted for the future using three alternative Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios (2.6, 4.5, and 8.5) of the Coupled Model Intercomparison Project Phase 6 (CMIP6). The G2 erosion model which is integrated with Machine Learning (ML) and Remote Sensing (RS) techniques were used to estimate soil erosion based on gauge observations of long-term precipitation, and climate and land use land cover (LULC) scenarios. The baseline model (2020) estimated soil erosion rates of 2.32 Mg ha−1 yr−1 under current conservation agriculture practices (CPs). Maintaining current CPs, future scenarios predict an 8 % to 21 % increase in soil erosion under different combinations of SSP-RCP climate and LULC change scenarios. The findings of this study can help policy makers for future conservation planning on maintaining soil fertility, mitigating environmental impacts, and promoting food security. [ABSTRACT FROM AUTHOR]

• Long-term expansion rates of 46 Urban Gullies in Kinshasa and Bukavu are quantified. • Gully widening is responsible for most of the gully expansion. • Expansion rates in sandy soils are mainly controlled by land cover and road density. • Expansion rates in clayey soils appear influenced by landslide dynamics. Urban gullies (UGs) are a growing concern in many tropical cities of the Global South. Addressing this new geo-hydrological hazard requires good insights into the rates and controlling factors of this process. Therefore, we investigate the expansion rates of a representative sample of UGs in Kinshasa (n = 17) and Bukavu (n = 29), two contrasting cities in D.R. Congo. We reconstruct long-term (10–17 years) expansion rates, making a distinction between headcut retreat and sidewall widening, and analyse the environmental factors potentially explaining these rates. Total expansion rates varying between 12.6 and 863 m2y-1. Most of this expansion happens through sidewall widening. In Kinshasa, which is mainly characterized by sandy soils, contrasts in expansion rates are mainly correlated to the characteristics of the upslope drainage area of the gullies. Especially the road density and a hypothetical runoff index (combining drainage area, land use and soil characteristics) explain a significant part of the observed variation. In Bukavu, such trends are less apparent. This is likely because the clayey nature of the soils provides more resistance against gullying, resulting in overall smaller and less actives UGs. Furthermore, the already low infiltration rates of these soils probably make the relative impact of urbanization on runoff production smaller. Our results also indicate that UGs located in recent landslides have higher gully expansion rates. The mechanisms behind remain poorly understood. Overall, our work opens promising perspectives to model and predict gully expansion rates in urban settings but may also guide efforts aiming to stabilize UGs. [ABSTRACT FROM AUTHOR]

• Soil water content (SWC) is determined as the outcomes of land use changes. • A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. • The shifts in organic matter sources over time and distinct mechanisms of degradation and preservation of SOM were underscore in wetlands following land use changes. Land use change in wetlands leads to significant losses of soil organic matter (SOM). Stable carbon (C) and nitrogen (N) isotopes offer insights into changes in C3/C4 vegetation, SOM sources, and decomposition processes. Yet, predicting the spatial–temporal dynamics of SOM contents and isotopes under land use changes remains challenging. This study delves into the effects of land use changes on soil organic carbon (SOC), total nitrogen (TN), δ13C and δ15N values, and soil physico-chemical properties and lignin phenols. Our results highlight the significance of soil water content (SWC) in determining the outcomes of land use changes. The conversion of wetland to cropland, forestland and construction land, led to notable reductions in SOC contents (8.71–56.33 %), and TN contents (7.87–37.12 %). Wetland conversion resulted in an enrichment of 13C and 15N abundance, with wetlands exhibiting the lowest δ13C (−25.57 to –22.89 ‰) and δ15N (2.66 to 6.67 ‰) values. A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. Key parameters, including bulk density (BD), C:N, the acid-to-aldehyde of vanillyl ((Ad/Al)v), lignin content (Λ 8), and total phosphorus (TP), were identified as influencing factors for both SOC and TN contents. When evaluating δ13C values, the most influential factors included silt, C:N, SOC, sand, and BD. These indicate the importance of soil chemical group (from 41 % to 21 %) in elucidating δ13C values declined, while lignin group's (from 9 % to 28 %) importance increased from topsoil to subsoil. The acid-to-aldehyde of syringyl ((Ad/Al)s), Λ 8 , C:N, BD and the cinnamyl-to-vanillyl ratio (C/V) were identified as the primary factors influencing δ15N values, with chemical group accounting for 36 % and lignin group for 48 % in topsoil, while physical group dominated 42 % in subsoil. Our findings underscore the shifts in SOM sources and distinct mechanisms of degradation/preservation of SOM following land use changes. [ABSTRACT FROM AUTHOR]

[Display omitted] Soils at 57 ancient Hindu temples in India are documented from field profiles as a basis for understanding livelihoods of the five cults of Puranic (Smarta) Hinduism during the first millennium CE. Similar soils were found at different temples of the same deity, but different kinds of soils at temples of different deities. Temples of Ganesha and Hanuman, for example, are alluvial Entisols and Vertisols, the principal cultivable soils of India. Temples of Vishnu and Lakshmi are well drained Alfisols and Aridisols suitable for grazing, housing and markets. Different soils supported different livelihoods, social classes and cults, such as servant (shudra) class for farmers Ganesha and Hanuman, and herder-merchant (vaishya) class for Vishnu and Lakshmi. This result matches accounts in the Matsya Purana (250–500 CE) specifying dark organic soils for shudras and red soil for vaishyas. Puranic Smarta polytheism may reflect amalgamation of different tribal traditions during expansion of Gupta and other Hindu empires. [ABSTRACT FROM AUTHOR]

• The agri-horticulture (AH) system exhibited the highest Carbon management index (CMI). • CMI increased at higher altitude in dry temperate Himalayas. • Passive carbon pool was higher under AH system than agriculture (A) by 16.2 %. • The highest Lability index was reported in A indicating lower stability than AH. Globally, land use management consistently changes the dynamics of labile and recalcitrant (non-labile) soil organic carbon (SOC) fractions. However, the effects vary depending on altitude, soils and management practices. The dry temperate north-western Himalayan region is characterized by the presence of diverse land use systems, however the comparison of these SOC fractions across various land use regimes is not well-documented in the area. This study reported the differences in labile and non-labile SOC fractions under the major land-use systems viz., Agriculture (A), Horticulture (H), Agri-horticulture (AH) and Grass fallow (OF) land in various soil-depth classes (0–20, 20–40 and 40–60 cm) along three altitudinal ranges i.e., 2200–2500, 2500–2800 and 2800–3100 m above mean sea level (m. a.m.s.l.) across the dry temperate region of north-western Himalayas. The lability index and carbon management index of the soils were determined using these fractions. The analysis affirmed the highest accumulation of active fractions viz., very-labile (2.66 mg g−1), and labile C fraction (2.55 mg g−1) under AH, while the highest recalcitrant fractions i.e., less-labile (3.34 mg g−1) and non-labile C fraction (7.46 mg g−1) was documented under H. Moreover, the Carbon Management Index (CMI) followed the order of AH > A > H > OF. All the SOC fractions, pools and CMI significantly increased with increase in altitude but declined at lower soil depths. The Pearson correlation analysis revealed that the CMI was positively correlated with the active C fractions i.e. C frac 1 (r = 0.96; p < 0.05) and C frac 2 (r = 0.9; p < 0.05). The higher active carbon pool and CMI (6.9–16 % and 4.1–15.7 % higher, respectively) under the AH may be due to the greater organic matter inputs to the soil under the agri-horticulture land use system. The findings of this study suggest that the soil can be managed sustainably by the adoption of stable land use systems such as agri-horticulture (owing to their higher CMI values) in the highly fragile dry temperate ecosystem of the north-western Himalayas. [ABSTRACT FROM AUTHOR]

• Determine soil zinc cycle using isotopic tracing from karst area. • Zinc behaviors strongly controlled by rock weathering and leaching processes. • Cultivation limits δ66Zn fractionation, grazing induces heavier δ66Zn compositions. Stable isotopes are increasingly employed to identify anthropogenic disturbances and geogenic processes of zinc (Zn) in terrestrial ecosystems. To reveal how land use affects the transformation of soil Zn, profile samples were collected from abandoned cropland (AC), grazing shrubland (GS), and natural land (secondary forest land, SF) in a typical karst area, and analyzed the Zn content and isotopic composition. Results exhibited that soil Zn contents in forest (SF: 72.50 ∼ 131.20 mg/kg) were more variable than those in agricultural lands (AC: 74.53 ∼ 112.20 mg/kg; GS: 48.26 ∼ 82.57 mg/kg). Rock weathering was the main contributor to soil Zn in each profile. Differences among profiles arose from partially assimilative Zn returning to the forest through plant debris, whereas leaching processes coupled with the consumption of crop production and livestock led to Zn loss. The δ66Zn varied in the largest range in SF (−0.26 ‰ to 0.04 ‰), and the extremums were both in the upper soil (0 to 80 cm). After the decomposition of plant debris, vegetation preferentially assimilated lighter δ66Zn, while retaining heavier δ66Zn in the surface soil. Moreover, the soil solution also had a lighter δ66Zn composition that leached downward. The narrowest range of δ66Zn composition was in AC (−0.14 ‰ to −0.02 ‰). The assimilation of crops exhausted the lighter δ66Zn fraction during cultivation, and the heavier δ66Zn fraction continued to be lost by leaching after stopping tillage. The δ66Zn composition ranged from −0.18 ‰ to 0.00 ‰ and decreased with depth in the GS. Animal excrement supplied unintentionally heavier δ66Zn compositions during grazing and obviously disturbed soil Zn behavior under the effects of vertical leaching. Both the content and isotopic composition showed that soil Zn dynamics were highly sensitive to agricultural activities. This study reveals a potential feedback mechanism for soil Zn behavior during agricultural disturbances, which is beneficial for optimizing land management in karst areas. [ABSTRACT FROM AUTHOR]

• Spatiotemporal DSL variation and associated forcings were explored at a semi-humid catchment. • Land use type was the dominant control on DSL variation at a catchment scale. • DSL response to meteorological factors differed between the semiarid and semi-humid catchments. • The mixed "forest/shrubland + grass" plantation type is recommended for the semi-humid catchment. The formation of dried soil layers (DSLs) is a broad consequence of climate change (i.e., through temperature increases and/or precipitation decreases) and poor land management practices, where these layers exist has severe negative effects (i.e., retardation of vegetation, negative water cycle balance) on the sustainability of restored ecosystems and health of agriculture. Because of the effort and time required, only sporadic in situ measurements on spatial and temporal DSL variation have been reported, particularly at a catchment scale. However, this information is essential for understanding mechanisms associated with evolutionary DSL processes as well as developing effective land management techniques. Accordingly, this study monitored soil water content to a 5 m depth over a 5-year period in a semi-humid catchment on the Loess Plateau while also investigating temporal DSL dynamics and dominant controls. In the semi-humid catchment, DSLs occurred at 90.7 % of all sampling sites. Spatially and temporally averaged DSL formation depth (DSLFD), DSL thickness (DSLT), and DSL soil water content (DSL-SWC) within the 0–5 m profile were 170 cm, 262 cm, and 9.52 %, respectively. Forest and shrubland DSL regimes were drier than those of grassland. These three DSL indices exhibited significant correlation with temperature variables, while only DSLFD variables significantly correlated to precipitation. Land use type was the predominant control of DSL variation at a catchment scale. A spatial DSLT variation comparison under different land use treatment positions determined the feasibility of planting grass at an upslope position and mixed forest/shrubland + grass at mid-slope and downslope positions in the semi-humid catchment, which provides a good case study for afforestation practices at a catchment scale. Findings from this study are intended to aid in catchment soil and water conservation, soil drought mitigation, and sustainable vegetation management practices on the Loess Plateau as well as other water-limited regions worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil properties and enzymatic activities varied across land use types and villages. • Agroforestry establishment accelerated soil enzymatic activities by 39.41–90.17%. • Cultivation caused massive decline in level and variability of enzymatic activities. • Climate, vegetation, and management practices determined the enzymatic activities. Soil microbial enzymatic activities, often used as indicators of soil health and fertility, are vulnerable to changes in climate and anthropogenic activities. This study analyses the responses of specific soil enzymatic activities– dehydrogenase (DHA), acid phosphatase (APH), β-glucosidase (BG) and urease (URE)– in Nitosols/Luvisols of the subtropical zone of the Central Himalaya, India. We investigated how these enzymatic activities vary with different land uses: arable land (AL), kitchen garden (KG) and peach orchard (PO), across four villages– Niglat, Kainchidham, Majhera and Syalikhet. Considering associated management practices, we quantified cumulative average soil enzymatic activities for the rabi season (2017–2018). In general, catalytic activity of the selected enzymes was highest in Syalikhet and lowest in Majhera. However, for land use types, enzymatic activities were lower in AL and KG (75.56–90.17% and 39.41–61.72%, respectively) compared to PO values. MANOVA analysis evaluated significant spatial differences (P < 0.001) in enzymatic activities. Soil enzymatic mean values were highest in the surface layer (0–10 cm) and decreased gradually with increasing depth. Parameters such as soil moisture content (SMC) and pH, along with vegetation, management practices, and nutrients such as SOC, TN, K, AP, and N forms (NH 4 +–N and NO 3 ––N) showed significant and strong correlations with all the soil enzyme activities (r = 0.40–0.97; P < 0.05). TN, SOC, K, SMC, pH, AP, NH 4 +- N, and clay content were key determining factors of soil enzymatic activities, explaining approximately 59% of the variation. These results suggest that using soil microbial enzymatic activities as soil quality indicators is a feasible approach to assess the impacts of vegetation, management practices, and soil profile depths in soils under different land use types/systems in selected impoverished villages of the fragile Central Himalaya, India. [ABSTRACT FROM AUTHOR]

• Channel dynamics of pseudomeandering rivers is poorly known. • The study river reacted very rapidly to sediment supply changes. • Deforestation resulted in an increase of sediment supply and in a braided channel. • Reforestation and gravel mining caused river incision and a low sinuosity channel. • Post mining sediment supply increase was a key factor in shaping channel morphology. Typically, pseudomeandering rivers are gravel-bed streams considered unstable and prone to turning into braided or meandering channels under the effect of external forcings. Channel changes of pseudomeandering rivers have not been investigated in detail so far. This paper analyses the response of a pseudomeandering river (the Cecina River in western central Italy) to variations of sediment supply resulting from streambed material mining and land use change throughout the last two centuries. Old maps and 11 sets of aerial images from 1954 to the present of four representative sites were used to measure the variation through time of bankfull width and channel sinuosity. The changes in the number of bends, chute channels, bank erosion, bend extension, migration and retraction were recorded and the main processes which favoured pseudomeandering river channel changes were investigated. The old maps indicate that in the first half of the XIX century, the study river had probably a braided morphology in response to the increase in sediment supply following the liberalization of deforestation. From the beginning of the XX century to the present, the river had a predominantly single thread, pseudomeandering morphology which did not change during about 20 years of intense gravel mining (the 1960s – mid-1980s) when the main response of the river was channel incision and narrowing. A few years after bed material extraction stopped the river started to widen, to increase channel sinuosity and consolidate its pseudomeandering morphology. The study confirms that marked variations in sediment supply are more effective than floods in triggering river channel changes. The study also shows that the pseudomeandering configuration is less unstable than previously highlighted in other scientific works. [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]

[Display omitted] • The SAS around the Danjiangkou Reservoir shows a clear spatial distribution. • Landscape and environmental factors and soil properties synergistically influence SAS. • Orchards displayed higher SAS compared to paddy fields and uplands. • SAS can be enhanced by reducing LPI and increasing landscape heterogeneity. Soil aggregate stability (SAS) plays a crucial role in determining the soil's resistance to erosion. Conducting a spatial variability analysis of SAS in the reservoir area, which is highly susceptible to soil degradation and erosion, can yield valuable insights for agricultural practices, landscape planning, and environmental management in this region. Nevertheless, existing research remains constrained in its capacity to accurately map and forecast soil aggregates at a spatial level. This study aims to investigate the spatial distribution of SAS in the Danjiangkou reservoir area, as well as to explore the intrinsic linkage mechanisms between changes in soil properties, environmental factors and landscape patterns and SAS. Results revealed significant spatial variations in SAS within the vicinity of the Danjiangkou reservoir area. Notably, soil properties (including clay, available potassium, soil organic matter, and available phosphorus), environmental factors (such as digital elevation model, slope, land surface temperature difference between seasons (ΔLST)), and landscape pattern (largest patch index (LPI), shannon's diversity index (SHDI), edge density (ED)) significantly affected the spatial variability of SAS, explaining 18.91%, 8.22%, and 8.17% of the total variability of soil SAS, respectively. Structural equation modeling results indicated that altering soil properties serves as the primary approach to enhance SAS. Furthermore, interventions targeting landscape factors such as LPI, SHDI, and ED, alongside environmental factors like ΔLST and slope, exert direct influences on SAS, while also indirectly impacting it through their effects on soil properties. These findings contribute to the design of land planning and soil and water conservation measures in the reservoir watershed, promoting its protection of soil structure and its ecological service function. [ABSTRACT FROM AUTHOR]

[Display omitted] • Establishing exclosures aids in vegetation restoration of degraded lands. • Exclosures of studied watersheds were limited in restoring degraded lands. • The efficacy of <11 & >11-year exclosures was different in restoring degraded lands. Land degradation is a severe environmental problem in the northern and northwestern Ethiopian highlands. As a response to increasing land degradation, rehabilitation of degraded grazing lands through exclosures (exclusion of farmers and domestic animals) has been undertaken. This study aimed to evaluate the effectiveness of 11 and 8-year exclosures in improving degraded landscapes in the Karita-Wuha and Dengora watersheds. It was assumed that the conditions on communal grazing lands at the time of the investigation corresponded to those at the establishment of exclosures. Vegetation was inventoried, and soil samples were collected and analyzed in 14 and 21 sampling sites selected from exclosures and communal grazing lands in Dengora and Karita-Wuha watersheds, respectively. Sampling plots (20 × 20 m) were established for soil sampling. In the two land uses, 10x10 m and 5x5 m sub-plots were used to survey trees and bushes/shrubs, respectively. Richness, diversity, evenness, and aboveground biomass (AGB) were evaluated using measurements from the vegetation inventory. Organic carbon (OC), total nitrogen (TN), and available phosphorus (AP) and their stocks were used as soil nutrient indicators. The result showed that exclosures aided in restoring vegetation in both watersheds and soil nutrient parameters in the Dengora watershed compared with communal grazing lands. In the Karita-Wuha watershed, there was significantly higher OC, TN, and their stocks in communal grazing land than exclosures (t -test, p < 0.05). These results are generally attributed to the fact that communal grazing lands were significantly degraded before exclosure and have yet to recover. As a result, exclosures of Dengora and Karita-Wuha watersheds were limited in restoring degraded landscapes. There have been differences in the effectiveness of < 11- and > 11-year exclosures in restoring degraded landscapes in the literature. The effectiveness of various aged exclosures in restoring degraded landscapes is likely variable and dependent on local biophysical parameters and land use systems. [ABSTRACT FROM AUTHOR]

Benthic metabolism is an essential process which plays a critical role in the carbon and nutrient cycles and in the transfer of material and energy in stream ecosystems. Benthic algae are one of principal primary producers in stream food webs that converts dissolved inorganic carbon to organic matter, and algae are more palatable basal resources for aquatic consumers due to its higher unsaturated fatty acid content than terrestrial carbon. Despite the importance of algae, few studies have investigated how the benthic metabolism is influenced by distal factors, such as upland land use and landscape configuration, and proximal factors, such as stream temperature, nutrient availability, and light availability at various spatial scales. Here, we measured the benthic metabolism and proximal factors at the outlet of 14 selected sub-catchments in a subtropical river. Land use and landscape metrics at the catchment, riparian, and reach scales were processed as distal factors. Using stepwise regression models, we found that the proximal factors, such as water temperature (WT) and total phosphorus (TP), significantly increased primary production, and that nitrate-nitrogen ( N O 3 - -N), pH, and electrical conductivity (EC) decreased gross primary production (GPP). Also, TP was positively correlated with respiration (R) while N O 3 - -N negatively impacted R. Structural equation modeling demonstrated that the patch cohesion index negatively affected GPP by restraining WT and TP at the catchment scale while the increased shape index elevated the WT and TP to promote GPP. Our results suggested that stream metabolism is vulnerable to anthropogenic disturbances, such as upland land use and landscape patterns. Thus, land use planning and administration, particularly at catchment scale, should consider how to minimize the influence of human activities on ecosystem function in streams. [ABSTRACT FROM AUTHOR]

The area of Burdur Lake gradually decreased from 211 to 122 km2 between 1975 and 2021. In this study, we explored the effects of time, environmental factors, and land uses on the spatial distribution of soil chemical properties (SOC, CaCO 3 , EC, and pH). In total 240 soil samples were taken (0–20 cm depth) at a 400 × 400 m grid sampling in the former lakebed, pasture, and agricultural fields representing a chronosequence. We found a considerable temporal and topographic trend in SOC, CaCO 3 , EC, pH, and vegetation density. The SOC, EC, and pH were higher in younger soils. Land use significantly affected soil properties. Natural vegetation species mainly grew in the pasture but only sparsely in the former lakebed areas. Salt-affected and alkaline soils and exposure time affected the density and spatial distribution of vegetation in the former lakebed and pasture areas. We tested different models to spatially predict soil properties and found that random forest had higher prediction accuracy for SOC (r2 = 0.50) and CaCO 3 (r2 = 0.36), whereas the cubist model had higher prediction accuracy for EC (r2 = 0.60) and pH (r2 = 0.38). We conclude that the vegetation density and distribution of SOC, CaCO 3 , EC, and pH were controlled by topography, time, and land use. The time and space-for-time substitution approach can be used to study soil chronosequence and biosequence in areas with shrinking lakes. [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]

• 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]

• 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]