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Plastic film mulching has been widely used to increase maize yield in the semiarid area of China. However, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial. A field experiment was initiated in 2013 with five different film mulching methods: (i) control method, flat planting without mulching (CK), (ii) flat planting with half film mulching (P), (iii) film mulching on ridges and planting in narrow furrows (S), (iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R). The effects on soil organic carbon (SOC) content, storage, and fractions, and on the carbon management index (CMI) were evaluated after nine consecutive years of plastic film mulching. The results showed that long-term plastic film mulching generally maintained the initial SOC level. Compared with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of SOC sequestration. Specifically, plastic film mulching significantly improved CMI, and increased the SOC content by 13.59%, SOC storage by 7.47% and easily oxidizable organic carbon (EOC) by 13.78% on average, but it reduced the other labile fractions. SOC sequestration and CMI were improved by refining the plastic film mulching methods. The S treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

Ecological stoichiometry facilitates the understanding of biogeochemical cycles by studying the balance among multiple elements in ecosystems. However, the spatial patterns of soil stoichiometry and their responses to land use in desertified land are unclear. In this study, we selected 525 sample points to collect topsoil (0–20 cm) samples throughout China's Horqin Sandy Land and measured soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP). We then calculated stoichiometric ratios (C:N:P). SOC (8.7 g kg−1), TN (0.9 g kg−1), and TP (0.3 g kg−1) were lower in this region than in Chinese and global terrestrial ecosystems due to aeolian desertification. SOC, TN, C:P, and N:P were significantly (p < 0.05) higher in grassland, followed by woodland, cropland, and sandy land. This sequence may result from the large number of dead roots that participate in the SOC turnover in grassland. TP was significantly higher in cropland due to fertilization. C:N did not differ significantly (p > 0.05) among grassland, woodland, and cropland because of the strong coupling relationship between SOC and TN. The values of SOC, TN, TP, C:P, and N:P in the Horqin Sandy Land were high in the north (dominated by mountain woodland and grassland) and were low in the south (dominated by desertified land). SOC, TN, and TP contents and C:N:P ratios were mainly affected by mean annual temperature (29.6%), land use (11.5%), and bulk density (11.4%) through their influence on soil microbial metabolism, litter and nutrient input, and soil structure, respectively. The results provide information on the overall changes in soil stoichiometry in the Horqin Sandy Land and its responses to land‐use changes, and can therefore guide ecological restoration in semiarid regions affected by desertification in the modern context of climate change. [ABSTRACT FROM AUTHOR]

Introduction: Rainfall events can determine a cascade of plant physiological and ecological processes, and there is considerable interest in the way that rainfall modifies plant water flux dynamics. Methods: The sap flow density (SF) of the planted species of Vitex negundo and Hippophae rhamnoides, on the Loess Plateau of China was monitored using the heat balance method from 2015 to 2017. Results and discussion: The results showed that SF responded differently to rainfall classes because of the changing meteorological and soil water content (SWC) conditions. For class 1: 0.2-2 mm, SF increased by 14.36-42.93% for the two species, which were mainly attributable to the effect of solar radiation and vapor pressure deficit after rainfall. For class 2: 2-10 mm, SF remained nearly stable for V. negundo and decreased for H. rhamnoides because of the relative humidity's effect. For class 3: > 10 mm, SF increased significantly because of increased SWC and the increasing response to solar radiation. The increased percentage of SF was relatively higher for V. negundo when rainfall was less than 20 mm, while the value was higher for H. rhamnoides when rainfall was greater than 10 mm. Further, V. negundo's water potential increased at the soil-root interface (y0) and yL, indicating that the plant, which has shallower roots and a coarser of leaf and bark texture, considered as anisohydric species and used precipitation-derived upper soil water to survive. The relatively consistent yL and y0 for H. rhamnoides, which has deep roots and leathery leaves, indicated that this species was considered as isohydric species and insensitive to the slight change in the soil water status. The differed response patter and water use strategies between the two species showed that species as V. negundo are more susceptible to frequent, but small rainfall events, while larger, but less frequent rainfall events benefit such species as H. rhamnoides. This study quantified the effect of environmental factors for SF variation. The results could help formulate a selection process to determine which species are more suitable for sustainable management in the afforestation activities under the context of more frequent and intense rainfall events. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of Ca on the biomass allocation strategies of tree species with different growth rates under drought conditions, we treated poplar (Populus canadensis cv) cuttings and mulberry (Morus alba) seedlings with two soil moisture levels (40 ± 5% and 80 ± 5% maximum water holding capacity) and two soil Ca levels (0 and 200 mg·kg−1 Ca2+) in a greenhouse experiment, and then measured the Ca uptake, growth, gas exchange parameters, biomass allocation, and leaf traits. Drought induced a reduction in biomass accumulation of poplar cuttings and mulberry seedlings, and the cuttings and seedlings exhibited different biomass allocation patterns in response to drought stress. Under Ca0 treatment, poplar cuttings allocated more biomass to leaves and less biomass to stems under drought conditions, leading to an increased leaf/stem (L/St) ratio and higher SLA than under moist conditions in order to maintain higher Pn, and had enhanced WUE to cope with drought stress. Under the same treatment, mulberry seedlings allocated more biomass to roots and less biomass to stems, leading to an increased root/shoot (R/S) ratio and lower SLA, to improve drought resistance. Ca200 treatment decreased the growth of poplar cuttings and mulberry seedlings, whereas it enhanced the WUE, root growth, and R/S ratio of poplar cuttings and the WUE of mulberry seedlings, and alleviated drought stress in both species. [ABSTRACT FROM AUTHOR]

Gully erosion has been identified in recent decades as a global threat to people and property. This problem also affects the socioeconomic stability of societies and therefore limits their sustainable development, as it impacts a nonrenewable resource on a human scale, namely, soil. The focus of this study is to evaluate the prediction performance of four machine learning (ML) models: Logistic Regression (LR), classification and regression tree (CART), Linear Discriminate Analysis (LDA), and the k-Nearest Neighbors (kNN), which are novel approaches in gully erosion modeling research, particularly in semi-arid regions with a mountainous character. 204 samples of erosion areas and 204 samples of non-erosion areas were collected through field surveys and high-resolution satellite images, and 17 significant factors were considered. The dataset cells of samples (70% for training and 30% for testing) were randomly prepared to assess the robustness of the different models. The functional relevance between soil erosion and effective factors was computed using the ML models. The ML models were evaluated using different metrics, including accuracy, the kappa coefficient. kNN is the ideal model for this study. The value of the AUC from ROC considering the testing datasets of KNN is 0.93; the remaining models are associated to ideal AUC and are similar to kNN in terms of values. The AUC values from ROC of GLM, LDA, and CART for testing datasets are 0.90, 0.91, and 0.84, respectively. The value of accuracy considering the validation datasets of LDA, CART, KNN, and GLM are 0.85, 0.82, 0.89, 0.84 respectively. The values of Kappa of LDA, CART, and GLM for testing datasets are 0.70, 0.65, and 0.68, respectively. ML models, in particular KNN, GLM, and LDA, have achieved outstanding results in terms of creating soil erosion susceptibility maps. The maps created with the most reliable models could be a useful tool for sustainable management, watershed conservation and prevention of soil and water losses.

Water shortage and water pollution are two prominent issues in North China. Understanding hydrological cycle and water quality changes in response to pollution control measures is fundamental for a better water management there. Using coupled MIKE SHE/MIKE 11 modeling, various hydrological components in Yanghe Basin in a semiarid area of North China were quantified for three typical hydrological years and concentrations of COD and TP in a national monitoring section of Yanghe were evaluated with/without pollution control measures. The modeling results show that the underground water storage of Yanghe Basin becomes depleted due to evapotranspiration compensation and groundwater utilization regardless of hydrological condition, indicating an unsustainable in-situ water resource utilization. Water quality goals set for Yanghe (COD ≤ 20 mg/L and TP ≤ 0.2 mg/L) can hardly be achieved if pollution control measures are not taken, especially for a dry hydrological year. Depending on hydrological conditions, non-point source control technology-related projects in a 109-km2 village and a 7-km river-channel wetland in mainstream of Yanghe will have a positive effect or negligible effect on water quality improvement. To meet water quality goals, implementation of three wetlands is an effective and economic way. HIGHLIGHTS A coupled MIKE SHE/MIKE 11 model is constructed for Yanghe Basin in North China.; Yanghe Basin undergoes unsustainable water resource utilization, with evapotranspiration surpassing rainfall.; Demonstration water projects on a small scale have either a positive or negligible effect on water quality of Yanghe.; Implementation of three river-channel wetlands is an effective and economic way to achieve water quality goals.;

Abstract In grazing ecosystems, mature seeds fall directly to the soil to form the soil seed bank (SSB), or are ingested by grazing livestock to become part of the dung seed bank (DSB; i.e., seed circulation). Both the SSB and DSB form the basis for the natural regeneration of vegetation. However, little is known about the relationships between the SSB, DSB, and aboveground vegetation (AGV) community under different stocking rates (SRs). This study investigated the relationships between the SSB, seeds in Tan sheep (Ovis aries) dung, and AGV at different SRs (0, 2.7, 5.3, and 8.7 sheep ha–1) in a semiarid region of the Loess Plateau in China. We found that Tan sheep grazing increased the species richness heterogeneity of grassland vegetation, and negatively influenced the density of AGV. Under natural conditions, 17 species from soil‐borne seeds and 10 species from Tan sheep dung germinated. There was low species similarity between the soil and DSBs and AGV. Sheep SR and the seed banks (soil and dung) were negatively correlated with AGV. Seeds are cycled from herbage to livestock to soil during cold season grazing; the seasonal nature of this seed dispersal is an adaptation to harsh, semiarid environments. Increased seed bank diversity under sheep grazing facilitates grassland regeneration on the Loess Plateau, similarly to other semiarid regions globally.

In order to evaluate the impact of groundwater drainage on groundwater flow, the Hetaoyu coal field was taken as a case study in the Longdong area, China, where the coal seam was covered with multilayer aquifers. A three-dimensional unsteady groundwater flow model and a one-dimensional fracture water flow model were calculated by joint equations for changing hydrogeological structures under coal mining. According to the results, mine construction had greatly affected groundwater reserves in the Quaternary phreatic aquifer, Cretaceous Huanhe confined aquifer, and Luohe confined aquifer. The groundwater drainage was mainly from the Cretaceous aquifer, in which the aquifer reserves of the Luohe Formation decreased by 30,861.8 m3/m, accounting for about 92% of the total changes in local groundwater reserves. A drop funnel with an area of about 2.3 km2 would be formed under the groundwater discharge of 187.6 m3/h for the main inclined shaft excavation of the Hetaoyu coal mine. With the continuation of mining activities, the mine water flow will reach 806.83 m3/h and would result in descending funnel area of about 4.5 km2, the groundwater level drawdown at least 16 m, which would exceed the limited value regulated by the government. Therefore, in order to ensure the safety of coal mining and protect groundwater resources, the Hetaoyu Coal Mine departments should take some water loss prevention and control projects to reduce the drawdown of groundwater. [ABSTRACT FROM AUTHOR]

Recent frameworks have proposed that division of soil organic matter (SOM) into particulate and mineral-associated organic matter (POM and MAOM) can help us better understand SOM cycling and its responses to increasing atmospheric nitrogen (N) deposition. However, responses of these factions to N deposition with combination of their relative distribution across soil profile remain unclear. Here we determined total N and soil organic carbon (SOC) as POM and MAOM separately in soils at depths of 0–10, 30–40 and 70–100 cm after 10-year N addition (at rates of 50, 10, 2 and 0 g m−2 yr−1) in a typical steppe. We further calculated their stocks in POM, MAOM and bulk soil and detected their relationships with both physicochemical features and microbial properties. Nitrogen addition increased the stocks of SOC (POM: +23 %; MAOM: +11 %) and total N (POM: +27 %; MAOM: +10 %) in both POM and MAOM fractions in topsoil (0–10 cm), but increased only in MAOM in 30–40 cm (SOC: +24 %; total N: +24 %) and 70–100 cm (SOC: +15 %; total N: +13 %) soils. Moreover, the increasing effects were strengthened with increasing N addition rates. We found that the share of SOC and total N in the MAOM was slightly decreased by N addition in topsoil, but significantly increased in deeper soils. Soil physicochemical features exerted stronger controls than microbial properties in the distribution of SOC and total N in the two fractions regardless of soil depth. SOC and total N contents of MAOM were correlated negatively with soil pH across the soil profile, and were correlated positively with bulk soil total N, dissolved organic N and inorganic N. Our findings imply that more soil C would be stabilized as MAOM under increasing atmospheric N deposition, and therefore the C saturation level of MAOM should be a target for further studies and be considered in predicting SOM dynamics, especially in N-limited grassland ecosystems.

Coal mining activities not only damage the ecosystems located inside mining areas, but also affect the buffer areas located within a certain radius of the mining activities. Effectively identifying the range disturbed by mining activities is beneficial for guiding ecological restoration and ecological assessments in mining areas. However, methods for quantitatively identifying the range of disturbances associated with coal mining activities are still lacking. In this study, the phenological disturbance range index (PDRI) based on remote sensing observed vegetation phenology was proposed. Normalized difference vegetation index (NDVI) time series data were collected, and land surface phenology parameters were estimated in the Pinshuo mining area on the Loess Plateau. The proportion of the phenology-climate coupling relationship destroyed by human activities was then calculated. The range of mining activity disturbances was then determined by mutually validating the function-fitting and trajectory-segmentation algorithms. The results show that the proposed PDRI can effectively identify the extent of disturbances resulting from mining activities. Clear differences among the PDRIs reflecting mining activity disturbances, urbanization disturbances and natural states were found. Taking the Pingshuo mine as an example, the range of disturbances was approximately 11 ∼ 12 km, and shaft mining was found to have a greater impact than open pit mining. The PDRI proposed herein solves the initial problem from a climate-response perspective and can be used as a standardized scheme to detect the extent of disturbances resulting from coal mining activities. This study can also provide a reference for policy formulation and ecological compensation range.

Grassland degradation in the semiarid area of China is often attributed to overgrazing and expansion of irrigated agriculture without the consideration of groundwater. However, falling groundwater levels in the region have caused many problems for grassland ecology. In this paper,the typical sandy grassland- the Tongliao part of Horqin grassland was selected as the study area to study the spatial distribution of normalized difference vegetation index (NDVI) and the relationship between the NDVI and groundwater depth (GD) of each grassland pixel was studied. The temporal variation of the NDVI and its correlations with precipitation were investigated. The relationship between GD and vegetation species diversity in grassland was analyzed based on the vegetation survey. The results of the relation between GD and NDVI and vegetation species showed that GD can buffer the impact of increase in drought events on the vegetation because GD affected the composition and diversity of vegetation species. As the GD increases, the mean NDVI showed a trend of increasing first and then decreasing, and basically remained unchanged when the GD was greater than 3.5 m. The species diversity of grassland decreased with increasing GD and was not related to GD when GD was greater than 3.5 ∼ 4 m. Falling groundwater levels will cause great changes in the structure of grassland; specifically, azonal vegetation will gradually die and 3.5 m may be the critical GD needed to maintain the incomplete extinction of grassland azonal vegetation in the aeolian sandy soil. Correlation analysis proved that the correlation between NDVI and precipitation was significantly enhanced when GD increased sharply from 3 m to 6 m after 1999. This research indicates that the control of grassland degradation should pay attention to controlling the groundwater exploitation to recover a reasonable groundwater level, which was found to be necessary in the support of diverse and climate resilient of vegetation.

In grazing ecosystems, mature seeds fall directly to the soil to form the soil seed bank (SSB), or are ingested by grazing livestock to become part of the dung seed bank (DSB; i.e., seed circulation). Both the SSB and DSB form the basis for the natural regeneration of vegetation. However, little is known about the relationships between the SSB, DSB, and aboveground vegetation (AGV) community under different stocking rates (SRs). This study investigated the relationships between the SSB, seeds in Tan sheep (Ovis aries) dung, and AGV at different SRs (0, 2.7, 5.3, and 8.7 sheep ha–1) in a semiarid region of the Loess Plateau in China. We found that Tan sheep grazing increased the species richness heterogeneity of grassland vegetation, and negatively influenced the density of AGV. Under natural conditions, 17 species from soil‐borne seeds and 10 species from Tan sheep dung germinated. There was low species similarity between the soil and DSBs and AGV. Sheep SR and the seed banks (soil and dung) were negatively correlated with AGV. Seeds are cycled from herbage to livestock to soil during cold season grazing; the seasonal nature of this seed dispersal is an adaptation to harsh, semiarid environments. Increased seed bank diversity under sheep grazing facilitates grassland regeneration on the Loess Plateau, similarly to other semiarid regions globally. [ABSTRACT FROM AUTHOR]

This study examined the vulnerability and responses of smallholder farmers to climate change effects in Semiarid Areas of Bahi and Kongwa Districts. A total of 366 household heads were involved in this study. The study employed questionnaire, interviews and documentary review as data collection techniques. Archival data for temperature, rainfall and crop yields were collected for trend analysis. Descriptive and inferential statistics were used to analyse quantitative data, content analysis was employed to analyse qualitative data. Simple linear trend analysis and Mann Kendall were used to establish trends. The findings indicate that smallholder farmers in the study area have noted reduced rainfall, increased temperature and reduced production as indicators of climate change. Results from archival data indicate insignificant decline of rainfall, significant increase of temperature and insignificant decline of crop yields at 5% significance level. As a response to these changes, smallholder farmers reported to use improved crop varieties, change planting dates, use intercropping, out-migrating and change land use practices. Several challenges were reported to hinder effective adaptation including inadequate capital, limited soft loans, limited weather information and deficient extension services. It is concluded that the climate is changing in the study area calling for strengthening farmers' adaptive capacity. [ABSTRACT FROM AUTHOR]

In this manuscript, we have highlighted the negative impacts of climate change effects on rural tourism activities in a semi-arid climate area. Indigenous populations, tourism investors, ecosystems, and geodiversity suffer from the consequences of increasing temperature during the summer season and flooding in the winter season. Since most of the oases, ecosystems, and populations are located in valleys, we identify management challenges that are likely to arise to shed light on managerial decision-making that will be required. Rural tourism is practically the only activity promoting income in such a territory. The management of natural and cultural heritage products, within a conceptual framework of protection, has proven to be necessary. The best proposal at the moment is the creation of a Global Geopark, offering policies and management plans for conservation. [ABSTRACT FROM AUTHOR]

Taking the importance of agricultural production sustainability with limited resources to use efficiency in an arid area, afield experiment was designed to investigate the effect of three, Acacia trees (Acacia nilotica, A. seyal, and A. tortilis) planting combination on soil fertility and Sorghum bicolor L. growth and physiological performance. The sorghum planted in 7 strips between 14 rows of Acacia trees planting combinations and one treeless strip as control. Acacia species plantations significantly increase soil fertility in terms of available nitrogen (N), phosphorus (P), potassium (K) and organic carbon (OC) contents as compared to control, highest level of N and P content (59.01 ± 1.45 and 58.77 ± 1.10 mg/kg) was reported in strip between rows of A. tortilis. Although the highest net photosynthesis rate (Pn) and stomatal conductance (gs) recorded in plants grown between rows of pure A. torilis, and rows of A. torilis-A. seyal, but different Acacia significantly enhanced sorghum growth and physiology with reference to net photosynthesis rate, stomatal conductance and chlorophyll fluorescence (chlF). The results stated linear relation between soil nutrients (N, P, K), Pn, and chlF increasing soil fertility improve physiological performance of sorghum. In conclusion, the three Acacia improve soil fertility and sorghum growth. Generally, this plantation trial can be environment-friendly alternative agricultural practices in Saudi Arabia or any area with a similar ecological condition to amend the soil and improve crop performance.

Several methods have been used to model reality and explain soil pedogenesis and evolution. However, there is a lack of information about which soil properties truly condition soil quality indicators and indices particularly at the pedon scale and at different soil depths to be used in land management planning. Thus, the main goals of this research were: i) to assess differences in soil properties (particle size, saturation point, bulk density, soil organic carbon, pH and electrical conductivity) at different soil depths (0-30 and 30-60 cm); ii) to check their statistical correlation with soil quality indicators (CEC, total N, Olsen-P, available K, exchangeable Na, calcium carbonate equivalent, Fe, Mn, Zn, and Cu); and, iii) to elaborate a soil quality index and maps for each soil layer. To achieve this, forty-eight soil samples were analysed in the laboratory and subjected to statistical analyses by ANOVA, Spearman Rank coefficients and Principal Component Analyses. Finally, a soil quality index was developed based on indicators of sensitivity. The study was conducted in a semiarid catchment in northeast Iran with irrigated farming and well-documented land degradation issues. We found that: i) organic carbon and bulk density were not similar in the topsoil and subsoil; ii) calcium carbonate and sand content conditioned organic carbon content and bulk density; iii) organic carbon showed the highest correlations with soil quality indicators; iv) particle size conditioned cation-exchange capacity; and, v) heavy metals such as Mn and Cu were highly correlated with organic carbon due to non-suitable agricultural practices. Based on the communality analysis to map of soil quality, CEC, Mn, Zn, and Cu had the highest weights (≥0.11) at both depths, coinciding with the same level of relevance in the multivariate analysis. Exchangeable Na, CaCO3, and Fe had the lowest weights (≤0.1) and N, P, and K had intermediate weights (0.1- 0.11). In general, the map of the soil quality index shows a lower soil quality in the subsoil increment than in the topsoil.

As a typical semiarid farming-pastoral ecotone sensitive to the environmennt, the Plain of West Liaohe Basin (WLBP) is currently experiencing drastic environmental changes. To identify how environmental change affect vegetation in the WLBP, we analysed spatiotemporal variation characteristics of Ecological environment factors based on monthly and annual air temperature (T), precipitation (P) and Normalized Difference Vegetation Index (NDVI) from 1982 to 2015. And the correlations between them were investigated by correlation analysis (Simple correlation, partial correlation and complex correlation) at temporal and spatial scale. The results showed that: (1) the vegetation growth of the WLBP showed ameliorated trend, with a change rate of 0.004/yr.; (2) P was more sensitive to NDVI than T; (3) and the influence of hydrothermal changes on vegetation growth was more significant than that of the change of single climate factors at time scales; (4) the effects of anthropogenic factors on vegetation change were 75.07% (1982–1993) and 98.08% (1994–2015), respectively. At the temp-special scales, P&T and land use type change (LUCC) were the main climatic and anthropogenic factors that affect vegetation changes, respectively. [ABSTRACT FROM AUTHOR]

Aims Accurate prediction of spatiotemporal variations in carbon and water fluxes of heterogeneous landscape is critical to comprehensively address the effects of climate change and vegetation dynamics on landscape and regional carbon and water cycling. Methods A field study was conducted to characterize the seasonal variations in gas fluxes and explore their relationships with abiotic and biotic factors in a small grassland landscape. Daytime carbon and water fluxes including net ecosystem exchange, gross ecosystem productivity, ecosystem respiration and evapotranspiration (ET) were measured for three types of grassland patches over a growing season using the closed chamber method. The key plant trait variables were measured, based on which community weighted mean (CWM) and functional variance (FDvar) were calculated. Important Findings The results showed that the temporal variations in the carbon and water fluxes were regulated by meteorological, soil and community functional variables. Inclusion of the CWM and FDvar of plant trait measures greatly improved the degree of explanation of the predict models. Specific leaf area and leaf δ13C content (Lδ13C) were the most important trait variables in affecting the variations of the gas fluxes. CWMs indices had greater importance than FDvar indices in predicting the variation of the C fluxes but FDvar indices were more important for ET than C fluxes. Our findings demonstrated that mass ratio hypothesis and the complementary effects hypothesis are not mutually exclusive but have different relative importance for different ecosystem processes. Community functional traits played important roles in predicting the spatiotemporal variations of carbon and water fluxes in semiarid grassland. [ABSTRACT FROM AUTHOR]

Taking the importance of agricultural production sustainability with limited resources to use efficiency in an arid area, afield experiment was designed to investigate the effect of three, Acacia trees (Acacia nilotica, A. seyal, and A. tortilis) planting combination on soil fertility and Sorghum bicolor L. growth and physiological performance. The sorghum planted in 7 strips between 14 rows of Acacia trees planting combinations and one treeless strip as control. Acacia species plantations significantly increase soil fertility in terms of available nitrogen (N), phosphorus (P), potassium (K) and organic carbon (OC) contents as compared to control, highest level of N and P content (59.01 ± 1.45 and 58.77 ± 1.10 mg/kg) was reported in strip between rows of A. tortilis. Although the highest net photosynthesis rate (Pn) and stomatal conductance (gs) recorded in plants grown between rows of pure A. torilis, and rows of A. torilis-A. seyal, but different Acacia significantly enhanced sorghum growth and physiology with reference to net photosynthesis rate, stomatal conductance and chlorophyll fluorescence (chlF). The results stated linear relation between soil nutrients (N, P, K), Pn, and chlF increasing soil fertility improve physiological performance of sorghum. In conclusion, the three Acacia improve soil fertility and sorghum growth. Generally, this plantation trial can be environment-friendly alternative agricultural practices in Saudi Arabia or any area with a similar ecological condition to amend the soil and improve crop performance. [ABSTRACT FROM AUTHOR]

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Abstract The Northwest Loess Plateau is a typical area of dryland agricultural production in China. Farmland mulching is often used to preserve the soil moisture and increase crop yields. However, the impacts of long-term farmland mulching practices on the soil fungal communities in the loessial soil in semiarid areas of China were less explored. Thus, we investigated the variations in the soil fungal communities under different mulching patterns using high-throughput sequencing to understand how different mulching practices affect these communities. The following treatments were investigated: ridge-furrow mulching pattern (R), flat plastic film mulching (P), flat biodegradable film mulching (B), flat straw mulching (S), and conventional flat planting without mulching as a control (CK). Farmland mulching practices significantly affected the soil fungal diversity and community structure by changing the soil properties. Compared with CK, the P and S treatments significantly increased the soil fungal diversity, thereby suggesting that these practices provided the most suitable growth environment for fungi. The soil moisture and nitrate nitrogen (NO 3 -N) content were the most important factors that affected the fungal diversity. Nonmetric multidimensional scaling ordination showed that the fungal communities in CK were separated from those in R and B treatments and closely clustered with the communities in the P and S treatments, thereby suggesting that the fungal community compositions differed slightly between the P and S treatments and the CK treatment, but the soil fungal community compositions in the R and B treatments differed significantly from that in CK. In addition, the fungal community composition depended primarily on the soil temperature and NO 3 -N. These results indicate that different farmland mulching practices affected the soil moisture, soil temperature, and NO 3 -N to change the soil fungal community distribution patterns in this region. Overall, the soil fungal diversity and abundance were both higher in the P treatment than the other treatments. Therefore, flat plastic film mulching is recommended for semiarid areas. Highlights • Farmland mulching changed the soil properties and the fungal community distribution. • Flat plastic film and straw mulching treatments improved the soil fungal diversity. • Fungal diversity response was primarily related to the soil moisture and NO 3 -N. • Fungal community composition primarily depended on the soil temperature and NO 3 -N. [ABSTRACT FROM AUTHOR]

Farmland mulching is widely used to preserve soil moisture and increase crop yield in the semiarid region of the Loess Plateau. However, the effect of different farmland mulching on soil bacterial communities is not clear. Therefore, the impact of a 5-year field management practice (surface mulching) on the soil bacterial communities was studied in dryland farmland of the Loess Plateau by using Illumina sequencing of the 16S rRNA gene. The following treatments were investigated: (1) ridge-furrow mulching pattern; (2) flat plastic film mulching; (3) flat biodegradable film mulching; (4) flat straw mulching; and (5) control (CK), conventional flat planting without mulch. All farmland mulching increased the diversity of soil bacteria and the diversity was greatest under the plastic film treatment. The dominant phyla across all soil samples were Proteobacteria , Acidobacteria , and Actinobacteria. Cluster analyses showed that bacterial communities under mulching treatments were different from that of CK. The bacterial community composition of plastic film and straw mulching treatments, biodegradable film and ridge-furrow mulching treatments were similar at the phylum level. Spearman correlation analysis indicated that the response of bacterial alpha-diversity was mainly negatively associated with the soil organic carbon and total nitrogen. The Mantel test showed that the beta-diversity depended primarily on the soil total nitrogen and soil temperature. The changes of the bacterial community distribution were significantly related to the soil moisture, which varied significantly with a range of 9.8–17.3 between treatments. These results indicated that soil properties changed after long-term farmland mulching, and these changes were related to soil bacterial diversity and community structure. According to this study, flat plastic firm mulching was found to being a good option for increasing soil bacterial diversity and richness and thereby potentially stabilize functional stability of soil biological processes. • Effects of four mulching methods on soil bacterial communities were compared. • Farmland mulching increased the diversity of the soil bacterial community. • Bacterial alpha diversity response was mainly related to SOC and TN. • Bacterial community composition was highly sensitive to the soil moisture. • Flat plastic film mulching is recommended in semi-arid areas of the loess plateau. [ABSTRACT FROM AUTHOR]

Understanding the spatiotemporal characteristics of hydrological components and their impacts on vegetation are critical for comprehending hydrological, climatological, and ecological processes under environmental change and solving future water management challenges. Innovative methods need to be developed in semiarid areas to analyze the special hydrological factors in the water resource systems of these areas. Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) were applied with the normalized difference vegetation index (NDVI) data in this paper to analyze spatiotemporal changes of hydrological factors in the Xiliaohe River Basin (XRB). The results showed that precipitation (P), evapotranspiration (ET) and temperature (T) had similar seasonal change patterns at rates of 0.05 cm/yr., 0.01 cm/yr. and −0.05 °C/yr., respectively. Total water storage change (TWSC) was consistent with the change trend of soil moisture change (SMC) and showed a fluctuating trend. Groundwater change (GWC) showed a decreasing trend at a rate of −0.43 cm/yr. P and ET had a greater impact on GLDAS data (R = 0.634, P < 0.05 and R = 0.686, P < 0.01, respectively) than on other factors. GWC was more sensitive to changes in T (R = 0.570, P < 0.05). Furthermore, a lag period of 0 to 1 months was observed for the effects of P and ET on TWSC and GLDAS. NDVI showed an upward trend at a rate of 0.001 yr−1 between 2002 and 2014. A spatial distribution of NDVI was heterogeneous in the study area. ET, GLDAS and GWC in growing season limited vegetation growth and were more important than other factors in XRB. The results may contribute to an understanding of the relationships between the hydrological cycle and climate change and provide scientific support for local environmental management.

Schinopsis brasiliensis is an endangered tree species found in the Caatinga biome. It presents a characteristic slow development and difficult propagation, although it has been traditionally exploited in the region. Application of arbuscular mycorrhizal fungi (AMF) and phosphorus (P) fertilization may be beneficial to S. brasiliensis development at the seedling stage, which at the same time may help species conservation and the recovery of degraded areas in the Caatinga biome. We assessed the response of S. brasiliensis to AMF inoculation (Claroideoglomus etunicatum and Acaulospora longula) and P fertilization (0, 12, 24, and 48 mg dm−3 addition of P2O5). S. brasiliensis responded positively to both AMF inoculation and P fertilization. At low P concentrations, the inoculated plants showed higher leaf area and enhanced vegetative development, nutrient content and biomass production compared with non-inoculated plants. Conversely, increasing levels of P fertilization decreased the level of mycorrhizal colonization, plant responsiveness to inoculation, and spore production in C. etunicatum. Thus, P concentrations were able to influence the response of S. brasiliensis to mycorrhization and responsiveness to increased mycorrhization with the decrease in P availability. These results showed that mycorrhizal symbiosis plays an essential role in the development of S. brasiliensis.

To evaluate the effects of straw belt-covering on soil temperature and yield of winter wheat in rain-fed semiarid region in Northwest China, five mulching modes, including flat field planting without any mulching (CK), whole plastic film mulching (PM), straw mulching by 30 cm covering belt with an interval of 30 cm planting belt with three-row sowing (SM1), straw mulching by 40 cm covering belt with an interval of 40 cm planting belt with four-row sowing (SM2), and straw mulching by 50 cm covering belt with an interval of 50 cm planting belt with five-row sowing (SM3), were set by two-year fixed-site trails in 2013-2015. The results showed that soil temperature significantly varied among different growth stages and soil layers in all treatments. SM1, SM2 and SM3 significantly decreased soil temperature by 1.0-1.3 °C, 0.7-0.9 °C and 0.7-1.1 °C in the 0-25 cm soil layer, respectively. The mulching had double effects with increasing and decreasing soil temperatures. The straw mulching significantly increased soil temperature in the duration of seedling to overwintering stage, but greatly decreased soil temperature in the duration of reviving to mature stage. The temperature-increasing effect of film mulching was stronger than that of straw mulching, which was opposite to the temperature-decreasing effect. Straw mulching significantly reduced in the effective accumulated temperature and the daily temperature variations during the whole growth stages. The effective accumulated temperature under straw mulching decreased by 3.433.5 °C, d, and the soil temperature difference decreased by 0.6-2.0 T. During over-wintering stage, the straw mulching showed a higher average soil temperature (0.2-0.3 °C,) and negative accumulated temperature (0.4-17.0 °C, d) than those under the CK. The straw mulching significantly increased grain yield by 11.9%-19.5%. The variations of spikes per unit area were the main factor responsible for yield difference. The findings indicated that that straw mulching method is suitable for winter wheat production in rain-fed region of Northwest China. [ABSTRACT FROM AUTHOR]

Fallow tillage methods play a major role in improving soil water storage, water use efficiency and hence grain yield in winter wheat ( Triticum aestivum L.) cropping system in southeast Loess Plateau. However, the efficacy and stability of such methods need to be further validated in long-term field observation. From 2009–2015, a 7-year filed experiment was established in winter wheat fields at Wenxi Agriculture Station, semiarid southeast Loess Plateau. The objectives were to determine the responses of soil water storage, utilization and yield formation to three different tillage methods: including deep ploughing, subsoiling and no-tillage. Our results indicated that compared to no-tillage, the soil water storage (0–300 cm depth) was averagely increased by 7.8% and 6.0% during fallow season, 13.7% and 9.8% in growing season under deep ploughing and subsoiling respectively. Furthermore, the increasing magnitude in soil water due to deep ploughing and subsoiling was, on average, 10.1% and 5.5% higher in dry season than that in wet one. Improved soil water condition under deep ploughing and subsoiling significantly increased the ear number and grain yield by 20.2% and 15.9%, 30.8% and 25.8% respectively, but did not affect seed number and weight of thousand seed over the experimental seasons. Moreover, grain yields under deep ploughing and subsoiling were averagely increased by 35.2% and 24.8% in dry season, 28.7% and 20.6% in wet season respectively. Accordingly, water use efficiency and precipitation use efficiency were increased by 12.1% and 31.9% under deep ploughing, 11.1% and 25.0% under subsoiling respectively. Critically, we found that with an increase of 10% water storage efficiency during fallow season, ear number, grain yield and WUE could be increased by 0.2 million ha −1 , 241.1 kg ha −1 and 0.6 kg ha −1  mm −1 respectively. Our study clearly indicated that deep ploughing in fallow season should be adopted as a promising strategy to retain soil water availability and hence boost wheat productivity in semiarid southeast Loess Plateau. [ABSTRACT FROM AUTHOR]

Deficiency of surface water resources in semiarid area makes the groundwater the most preferred resource to assure population increased needs. In this research we are going to quantify the rate of groundwater recharge using new hybrid model tack in interest the annual rainfall and the average annual temperature and the geological characteristics of the area. This hybrid model was tested and calibrated using a chemical tracer method called Chloride mass balance method (CMB). This hybrid model is a combination between general hydrogeological model and a hydrological model. We have tested this model in an aquifer complex in the region of Djelfa (Algeria). Performance of this model was verified by five criteria [Nash, mean absolute error (MAE), Root mean square error (RMSE), the coefficient of determination and the arithmetic mean error (AME)]. These new approximations facilitate the groundwater management in semi-arid areas; this model is a perfection and amelioration of the model developed by Chibane et al. This model gives a very interesting result, with low uncertainty. A new recharge class diagram was established by our model to get rapidly and quickly the groundwater recharge value for any area in semi-arid region, using temperature and rainfall. [ABSTRACT FROM AUTHOR]

Precipitation is usually the primary source of water for the hydrological cycle in a semiarid area. However, dew occurs frequently and affects water circulation dramatically in the west of Jilin Province in China. Measurements of the amount of dew formed and precipitation were carried out from July 2012 to October 2013 in the Momoge Natural Reserve. The results indicated that moisture from primary precipitation in the summer originated from the East Asian monsoon and was affected by the atmospheric circulation in the middle and high latitudes of Eurasia in the winter. The dew amount was approximately 19.44 mm (approximately 5% of the total rainfall amount), consisting of the evapotranspiration in the local area and atmospheric moisture. Dew also supplies nutrients to the local vegetation. The maximum contribution of total nitrogen, total phosphorus, and potassium in unit corn area could reach 288.60, 27.46, and 291.63 mg/m2 in half a month, respectively. The wind speed, relative humidity, and lowest temperature were the primary factors that dramatically affected dew formation and amount. As an additional source of fresh water, dew not only had a positive impact on the ecosystem in arid and semiarid zones but also played an important role in the local water cycle and other ecological processes. This research has important implications for water circulation and land use management. [ABSTRACT FROM AUTHOR]

Introduction: Rainfall events can determine a cascade of plant physiological and ecological processes, and there is considerable interest in the way that rainfall modifies plant water flux dynamics., Methods: The sap flow density (SF) of the planted species of Vitex negundo and Hippophae rhamnoides , on the Loess Plateau of China was monitored using the heat balance method from 2015 to 2017., Results and Discussion: The results showed that SF responded differently to rainfall classes because of the changing meteorological and soil water content (SWC) conditions. For class 1: 0.2-2 mm, SF increased by 14.36-42.93% for the two species, which were mainly attributable to the effect of solar radiation and vapor pressure deficit after rainfall. For class 2: 2-10 mm, SF remained nearly stable for V. negundo and decreased for H. rhamnoides because of the relative humidity's effect. For class 3: > 10 mm, SF increased significantly because of increased SWC and the increasing response to solar radiation. The increased percentage of SF was relatively higher for V. negundo when rainfall was less than 20 mm, while the value was higher for H. rhamnoides when rainfall was greater than 10 mm. Further, V. negundo 's water potential increased at the soil-root interface (ψ 0 ) and ψ L , indicating that the plant, which has shallower roots and a coarser of leaf and bark texture, considered as anisohydric species and used precipitation-derived upper soil water to survive. The relatively consistent ψ L and ψ 0 for H. rhamnoides , which has deep roots and leathery leaves, indicated that this species was considered as isohydric species and insensitive to the slight change in the soil water status. The differed response patter and water use strategies between the two species showed that species as V. negundo are more susceptible to frequent, but small rainfall events, while larger, but less frequent rainfall events benefit such species as H. rhamnoides . This study quantified the effect of environmental factors for SF variation. The results could help formulate a selection process to determine which species are more suitable for sustainable management in the afforestation activities under the context of more frequent and intense rainfall events., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Fang, Lu, Liu, Li and Wang.)

The ridge and furrow rainfall harvesting system is known to be an effective planting method for improving rainwater utilization, but suitable fertilizer application rates for foxtail millet under RFRH planting have not yet been determined. In order to clarify the effects of fertilization under RFRH system and excavate its potential to enhance crop yield, we conducted field experiments during 2012-2015 at the Dryland Agricultural Experiment Station, Pengyang city, Ningxia, at the Loess Plateau, China. The experimental site was located at a longitude of 35°79'E and latitude of 106°48'N, at an elevation of 1658 m above sea level. The field experiment included 2 planting patterns (R, ridge and furrow rainfall harvesting planting; T, traditional flat planting) and 4 fertilizer level (F0, no fertilizer; F1, N:P2O5 at 93:48 kg/hm2; F2, N:P2O5 at 186:96 kg/hm2, F3, N:P2O5 at 279:144 kg/hm2), the R model used ridge and furrow widths of 60 cm, a ridge height of 15 cm, and the ridges were mulched with plastic film. The soil moisture of 0-20 cm profile was measured using a manual soil ferric auger at sowing, heading and harvesting stage, soil water storage and crop water consumption were calculated. The dry matter at different growth stages, yield and its components, use efficiency of water and fertilizer, and economic profit were measured. The 4-year experiment results showed that fertilization generally had a significantly positive effect on plant growth, yield formation and water use efficiency. As the increase of fertilizer input rate, the dry matter per plant, grain yield, WUE and economic profit under R planting were improving, but there was no significant increase when fertilizer rate beyond F2 in which the agronomy efficiency decreased, which indicated F2 was a suitable fertilizer input level for R planting. Compare to no fertilizer, the grain yield of the R treatment significantly improved by 28.1%-85.3%, respectively. Compared to traditional flat planting, the R planting could increase yield by 8.3% and 7.8% in the normal year, but decrease yield by 6.1% in the wet year (2012). The yield-increasing effect was best in the medium and low fertilizer treatments. In addition, the R treatment could reduce water consumption than the T treatment. The water consumption of R treatment was 18.3-26.8 mm lower than the T treatment in 2012-2015. In the normal year, the different planting model affected significantly the grain number per ear and harvest index, but did not affect the 1000-seeds weight. The rain number per ear and harvest index of the R treatment was 8.4% and 4.2% higher than the T treatment (P<0.05). In wet year, the planting model did not significantly affect these yield components of millet. Compared with the T treatment, the R treatment significantly increased the water use efficiency of millet in the normal year. The increase under the middle fertilizer treatment was 14.6% and 15.1%. The R treatment could increase agronomy efficiency than the T treatment, which increased with reduction of fertilizer application amount. This effect was better in the normal year than in the wet year. Among all the treatments, the medium fertilizer application in the R treatment in the normal year increased the yield by 7.6%, water use efficiency by 14.9%, agronomy efficiency by 9.9% and economic profit by 6.2% than the T treatment. Therefore, the RFRH system combine with F2 (N: P2O5 at 186:96 kg/hm2) was a reasonable and efficient model for foxtail millet cultivation in semi-arid areas. [ABSTRACT FROM AUTHOR]

The existence of long and reliable streamflow data records is essential to establishing strategies for the operation of water resources systems. In areas where streamflow data records are limited or present missing values, rainfall-runoff models are typically used for reconstruction and/or extension of river flow series. The main objective of this paper is to verify the application of Kohonen Neural Networks (KNN) for estimating streamflows in Piancó River. The Piancó River basin is located in the Brazilian semiarid region, an area devoid of hydrometeorological data and characterized by recurrent periods of water scarcity. The KNN are unsupervised neural networks that cluster data into groups according to their similarities. Such models are able to classify data vectors even when there are missing values in some of its components, a very common situation in rainfall-runoff modeling. Twenty two years of rainfall and streamflow monthly data were used in order to calibrate and test the proposed model. Statistical indexes were chose as criteria for evaluating the performance of the KNN model under four different scenarios of input data. The results show that the proposed model was able to provide reliable estimations even when there were missing values in the input data set.

In this application-based study, the influence of the catchment discretization on the optimization of runoff-erosion modeling using a particle swarm optimization to a physically-based erosion model named WESP (Watershed Erosion Simulation Program) is conducted. This study is carried in the semiarid region of Brazil, more precisely in a micro-catchment (MCN3) of Sumé Experimental Basin. A comparative assessment is done by statistical analysis and mean relative error (MRE) in order to evaluate the performance of the optimization technique when discretizing the catchment in different ways. Thus, the catchment is represented in three ways of discretization (i.e., n1 = 4 elements, n2 = 10 elements and n3 = 23 elements). The difficulties involved in calibration of physically-based erosion models have been partly attributable to the lack of robust optimization tools, hence several robust optimization techniques have been proposed in the past years; however, the way the catchment is represented could interfere on the results. Thus, this paper presents the essential concepts of the runoff-erosion WESP model, the global optimization method known as Repulsive Particle Swarm (RPS), and the optimization results using the three catchment discretization. The results show that there are small differences among the calculated sediment yield using the three ways of basin discretization, although the 23 elements division seems to give the best results.

Check dams are the most widespread structures for successfully retaining water and checking erosion on the semiarid portions of China's Loess Plateau. However, in the process of check dam planning and construction, difficulties in identifying the weights of influential factors, balancing all factors and making decisions are common problems that seriously restrict rapid socioeconomic development. With the goals of determining potential check dam construction sites and holistically maximizing a projected check dam array's water resource, ecosystem and socioeconomic benefits (taking into account the water shortage and ecological fragility in semiarid areas), a water-saving-ecological check dam site optimization model (WCSOM) was developed. The WCSOM, with newly added water-saving factors, was applied to the selection of check dam sites in the Sijiagou Basin. The model showed that the ecological and the water-saving factors were the top two weights, accounting for 59.88% of the total weight. The top three influencing elements were conservation of water sources, flood prevention capacity and check dam control area, which were part of the ecological, socioeconomic and economic factors, respectively, accounting for 37.77% of the total weight. The scores of larger-scale check dam sites in the basin were generally higher, while the scores of smaller-scale sites were generally lower. The use of the WCSOM in watershed planning will allow a more efficient use of water and soil resources and greatly alleviate water crises in this semiarid area. The WCSOM can be further applied in other regions by adjusting the criterion and index hierarchies, and it can provide technical support for both the planning and rapid development of a check dam system. • A Water-saving-ecological Check Dam Site Optimization Model (WCSOM) is proposed. • WCSOM can maximize the overall benefits to optimal check dam site location. • WCSOM can identify the influencing factors weights accurately and efficiently. • WCSOM allow a more efficient water and soil resources utilization. [ABSTRACT FROM AUTHOR]

Water scarcity in the dry season is a vital problem in dryland regions such as northeastern Brazil. Water supplies in these areas often come from numerous reservoirs of various sizes. However, inventory data for these reservoirs is often limited due to the expense and time required for their acquisition via field surveys, particularly in remote areas. Remote sensing techniques provide a valuable alternative to conventional reservoir bathymetric surveys for water resource management. In this study single pass TanDEM-X data acquired in bistatic mode were used to generate digital elevation models (DEMs) in the Madalena catchment, northeastern Brazil. Validation with differential global positioning system (DGPS) data from field measurements indicated an absolute elevation accuracy of approximately 1 m for the TanDEM-X derived DEMs (TDX DEMs). The DEMs derived from TanDEM-X data acquired at low water levels show significant advantages over bathymetric maps derived from field survey, particularly with regard to coverage, evenly distributed measurements and replication of reservoir shape. Furthermore, by mapping the dry reservoir bottoms with TanDEM-X data, TDX DEMs are free of emergent and submerged macrophytes, independent of water depth (e.g. > 10 m), water quality and even weather conditions. Thus, the method is superior to other existing bathymetric mapping approaches, particularly for inland water bodies. The proposed approach relies on (nearly) dry reservoir conditions at times of image acquisition and is thus restricted to areas that show considerable water levels variations. However, comparisons between TDX DEM and the bathymetric map derived from field surveys show that the amount of water retained during the dry phase has only marginal impact on the total water volume derivation from TDX DEM. Overall, DEMs generated from bistatic TanDEM-X data acquired in low water periods constitute a useful and efficient data source for deriving reservoir bathymetry and show great potential in large scale application. [ABSTRACT FROM AUTHOR]