China Loess Research Articles

Effect of mulching and organic manure on maize yield, water, and nitrogen use efficiency in the Loess Plateau of China.

Current agricultural practices prioritize intensive food production, often at the expense of environmental sustainability. This approach results in greenhouse gas emissions and groundwater pollution due to over-fertilization. In contrast, organic agriculture promotes a more efficient use of non-renewable energy, improves soil quality, and reduces ecological damage. However, the effects of mulching and organic manure on maize yield, water use efficiency (WUE), and nitrogen use efficiency (NUE) in China's Loess Plateau have not been sufficiently researched. In 2017 and 2018, an experiment utilizing a randomized complete block design with two factors (two mulching levels × three organic nitrogen application rates) was conducted. The water content of the upper soil layer was found to be 12.6% to 19.4% higher than that of the subsoil layer. Across all soil depths and years, the soil nitrate-N content in mulched treatments was 10% to 31.8% greater than in non-mulched treatments with varying organic nitrogen rates. Additionally, mulching resulted in an increase in grain yield of 9.4% in 2017 and 8.9% in 2018 compared to non-mulched treatments. A significant interaction was observed between mulching and organic nitrogen application rate concerning WUE, alongside a negative correlation between WUE and NUE. These findings suggest that the application of 270 kg N ha-1 of sheep manure in conjunction with mulching is a highly recommended practice for the Loess Plateau, thereby supporting sustainable agricultural strategies.

Detecting and attributing the impact of human activities on grassland aboveground biomass in China's Loess Plateau

Human activities significantly influence grassland ecosystem functions, particularly plant biomass. However, the direction and magnitude of these effects remain insufficiently explored. Herein, we quantitively assessed both the positive and negative effects of various human activities on grassland aboveground biomass (AGB) in China's Loess Plateau from 2000 to 2022. The results indicated that the magnitudes of positive effects increased by 0.29 g m−2 per year, whereas the negative effects decreased by 0.31 g m−2 per year. Spatially, 32 % of the grasslands experienced significant positive effects, whereas the rest grasslands faced negative effects. Notably, only 20 % of the areas with negative effects showed worsening trends mainly due to ecological restoration, sustainable agriculture, and population migration. Agricultural production activities and population changes emerged as dominant factors, with some activities, like livestock farming, exhibiting dual effects (i.e., positive and negative effects) on AGB. These findings underscore the complexity of human activities in affecting the grassland production function and highlight the necessity for balanced management strategies to sustain grassland productivity and resilience.

To Investigate the Impact of Land Use Change on the Potential Groundwater Recharge on Hillslope With Deep Loess Deposits

ABSTRACTAccurately estimating groundwater recharge in hilly areas with limited water and thick vadose zones is challenging. This study investigated the impact of land use changes on groundwater recharge at a hillslope scale of Yuanzegou Watershed in China's Loess Plateau. Three adjacent hillslopes were selected for three different land uses: arbor (jujube, Ziziphus jujuba Mill.), subshrub (native grass, Artemisia gmelinii), and crop (millet, Setaria italica). Soil cores (as deep as 10–16/18 m) were collected at each of the three landscape positions on a hillslope. Reported tritium profiles in the watershed were used to estimate the net chloride input into vadose zone on hillslope associated with inverse chloride mass balance (CMB) method/chloride accumulation method (CAM). Soil water content and chloride profiles in the study were measured to determine recharge rates at each landscape position beneath different vegetation types. For the first time, we evaluated the actual chloride input into vadose zone on hillslopes as 540.2 ± 23.8 mg m−2 yr.−1, excluding the impact of runoff. Then, estimated recharge rates ranged from 42.7 ± 3.5 to 62.4 ± 4.7 mm yr.−1, consistent with nearby studies. Results showed that groundwater recharge does not change with landscape position except for higher value on upslope beneath subshrub hillslope. In contrast, groundwater recharge did significantly reduce by 12.9% ± 5.4% and 26.5% ± 4.5% after conversion from cropland to subshrub/arbor on the hillslope, respectively. Our findings contribute to understanding the ecohydrological effects of land use changes on groundwater recharge on hillslope and help to select suitable afforested vegetation for greening efforts in water‐limited hilly areas, with a priority on groundwater safety.

Afforestation Reduces Deep Soil Carbon Sequestration in Semiarid Regions: Lessons From Variations of Soil Water and Carbon Along Afforestation Stages in China's Loess Plateau

AbstractAfforestation represents an effective approach for ecosystem restoration and carbon (C) sequestration. Nonetheless, it poses notable challenges concerning water depletion and soil drought in (semi)arid regions. The underlying mechanisms regulating the influence of afforestation on soil carbon‐water dynamics, particularly how deep soil C reacts to afforestation‐induced soil drying, remain largely unclear. This study examined the variations of soil water content (SWC), soil organic carbon (SOC), and soil inorganic carbon (SIC) in 500 cm depth along four afforestation stages: abandoned grasslands, shrublands, and 20‐year and 40‐year Robinia pseudoacacia forests (RP20 and RP40) in the semiarid Loess Plateau, China. The results indicated that afforestation has significantly increased SWC (+26.6%), SOC (+44.5%), and SIC (+6.5%) in the shallow layer (0–100 cm) but caused evident soil drying (−60.8%), decrease in SOC (−37.8%), and slight reduction in SIC (−0.3%) in the deep layer (300–500 cm) when compared with grasslands. The seriously decline in the coupling coordination between soil C and SWC in the middle and deep layers indicates the unsustainability of afforestation especially for RP40. Structural equation model showed that the negative impact of afforestation on deep SOC through soil water depletion (−0.38) outweighed the direct positive impact of increased aboveground biomass (AGB) (+0.33). The negative impacts of decreased SWC and increased pH on deep SIC was close to the positive impacts of AGB. Afforestation has different effects on SOC and SIC across shallow and deep layers, and its negative effects on deep soil C should be fully integrated into future forest ecosystem restoration and management efforts.

Multidimensional multiscale complexity analysis of sediment dynamics in the Yanhe Watershed of the loess Plateau, China

The Yanhe Watershed, emblematic of the loess hilly-gully landscape and ecological fragility in China's Loess Plateau, has experienced significant soil erosion and extensive soil-water conservation measures. To elucidate sediment dynamics and identify influencing factors in this region from 1960 to 2020, a novel multidimensional multiscale complexity analysis (MMCA) method was developed, based on entropy and complexity perspectives. This method integrated the refined composite multiscale fuzzy entropy (RCMFE) with multidimensional complexity analysis, offering a nuanced evaluation of sediment complexity and its implications for water resource management and ecological restoration. The findings revealed two distinct stages of sediment complexity variations: 1971–1988 and 2000–present. During the first period, the operation of the Wangyao Reservoir predominantly influenced sediment dynamics, initially reducing sediment complexity through sediment interception but later increasing it during discharge phases, particularly at larger scales. After 2002, extensive vegetation restoration efforts significantly reduced sediment complexity but raised concerns about long-term ecosystem resilience. Over the past decade, urbanization and climate change have exacerbated sediment instability, especially over semi-annual scales. This study advocates for management strategies that prioritize ecosystem sustainability and address the challenges posed by climate change and urbanization, facilitating improved soil and water conservation efforts in the Yanhe Watershed and similar regions in the Loess Plateau.

Diurnal asymmetry of surface albedo in a semi‐arid grassland over the China's Loess Plateau

AbstractIn current land surface models or satellite remote sensing retrievals, clear‐sky surface albedo (α) is usually assumed to be symmetrical and relies only on the solar elevation angle (SEA). Based on 1‐min high‐resolution measurements of surface radiation fluxes, this study demonstrated that the diurnal variations of clear‐sky surface albedo exhibited a significant asymmetrical pattern in both summer and winter seasons over a semi‐arid grassland of the China's Loess Plateau. The results indicated that α values in the morning were generally larger than those in the afternoon at the same SEA, and diurnal asymmetry of surface albedo was distinctly prominent with SEA <40° in summer (before 9:30 a.m.) or SEA <20° in winter (before 10:00 am), and tended to diminish at midday. The averaged morning/afternoon albedo differences under sunny days were 0.05 (30.4%) and 0.09 (37.8%) in summer and winter seasons, respectively. Air relative humidity was positively correlated with the diurnal asymmetry of surface albedo, ascribed to probable formation of dew in the morning. Depression of the dew point was negatively linked to the morning/afternoon albedo differences, which was attributed to the strong scattering of incident sunlight by dewdrops could enhance the morning surface albedo. Such diurnal asymmetry of surface albedo should be included in the parameterization scheme of mesoscale and region‐scale climate models in the semi‐arid areas of China's Loess Plateau.

Soil desiccation in the context of vegetation restoration: A scientometric analysis

AbstractThis research aims to fill the gap in understanding the evolution of soil desiccation studies, focusing on its impact on sustainable crop production in China's Loess Plateau. The study explores trends, influential works, authors, journals, and emerging research areas within the field of soil desiccation. To achieve this, this study pioneers a comprehensive scientometric exploration of soil desiccation. The study analyzed 1952 publications on soil desiccation from January 2013 to December 2023, sourced from the Web of Science. Various co‐citation techniques such as author co‐citation analysis (ACA), document co‐citation analysis (DCA), journal co‐citation analysis (JCA), and keyword analysis are employed. Network development, visualization tools, and text‐mining methods are utilized to discern patterns and relationships within the dataset. Here, for the first time, nine distinct clusters were identified through DCA. The findings reveal the impactful emergence of significant clusters, such as the one focusing on the Loess Plateau, marking a significant advance in our understanding of soil desiccation. Multiple research frontiers or sub‐specialties emerge, including topics such as different vegetation types, the impact on grain yield, water use efficiency, growth, soil water content, hydraulic redistribution, drought, soil moisture, and modeling. This innovative scientometric review of soil desiccation outlines the current scientific and technological trends while identifying knowledge gaps. The findings are beneficial for researchers, graduate students, and professors interested in understanding research trajectories, pivotal publications, and influential scholars shaping this field.

Response of soil moisture to rainfall following deep soil drying in China's hilly loess lands

Deep soil drying is a physical soil phenomenon that has become increasingly characteristic to artificial afforestation on China's Loess Plateau. Current research is largely short of conclusive reports on soil moisture recovery following deep soil drying in afforested lands. In this study, a 10-m deep underground column was constructed at Pengyang Experimental Station in Ningxia. The CS650-CR1000 automatic soil moisture monitoring system and BLJW-4 small meteorological observation stations were used to respectively monitor soil moisture and meteorological conditions in the study area for the period 2014–2019. The local rainfall was classified and the characteristics of soil infiltration analyzed at both monthly and annual scales. The results showed that: i) Deep soil moisture recovery in the semi-arid Loess Plateau region depended mainly on 25–49.9 mm and >50 mm types of rainfall; together accounting for 35.44 % of the precipitation. ii) Deep soil moisture replenishment occurred mainly for the period from April to October. While this accounted for 30.13 % of the precipitation, evaporation loss accounted for 69.87 % of it. With increasing monthly rainfall (Pm), the variation in monthly infiltration depth (Zm) was quadratic in shape — where Zm = −0.0094 Pm2 + 3.7702 Pm (R2 = 0.9577). iii) At the annual scale, deep soil moisture replenishment was mainly driven by year-on-year infiltration water accumulation. This is because a single year precipitation infiltration was not enough to replenish deep soil moisture. The cumulative infiltration depth for 2014–2019 was 180, 260, 400, 700, 1000 > 1000 cm. It suggested that soil water infiltration and deep dry soil recovery occurred at different times under rainfed conditions in the semi-arid loess hills in China. This is key for in-depth studies of the hydrological process in dry soil regions.

Assessing catchment-scale groundwater discharge: Optimal tracers and factors analysis

Identifying streamwater-groundwater interactions (SGI) is crucial for effective water resource management, especially in arid and semi-arid regions. Despite the effectiveness of tracers in detecting these interactions, their large-scale application is challenged by the variability in tracer characteristics and natural conditions. This study addresses these challenges through extensive research across seven watersheds (7636−60,916 km2) in China's Loess Plateau (CLP). We utilized multiple physicochemical and stable isotope tracers (δ2H and δ18O) to elucidate the spatiotemporal variations and controlling factors of SGI, and to estimate uncertainties in quantifying SGI using various indicators during unidirectional water exchange periods. Our findings indicated that groundwater discharge into streamwater dominates SGI in the CLP, with mean discharge ratios (the percentage of river flow that originates from groundwater discharge) varying from 10% to 57%. Significant spatial variability was observed both across and within watersheds. The central watersheds exhibited lower discharge ratios (23 ± 11%) compared to the northern (29 ± 12%) and southern (25 ± 13%) watersheds. The upper reaches showed higher discharge ratios (28 ± 12%) compared to the middle and lower reaches (22 ± 8%). Loess thickness and vegetation primarily limit groundwater discharge by affecting groundwater storage and water flow velocity. The utilization of individual isotopic or hydrochemical indicators introduces large uncertainties in quantifying groundwater discharge ratios due to isotope fractionation or water-rock interaction, while the combination of these two indicators can reduce uncertainties in quantifying SGI. This study provides valuable insights for selecting environmental tracers to quantify SGI, contributing to sustainable water resource management in arid and semi-arid regions.

Responses of Soil Moisture to Gully Land Consolidation in Asian Areas with Monsoon Climate

Groundwater resources are essential for sustaining ecosystems and human activities, especially under the pressures of climate change. This study employed Electrical Resistivity Tomography (ERT) to assess the impact of Gully Land Consolidation (GLC) engineering on the groundwater hydrological field of small watersheds in the China Loess Plateau (CLP). Results revealed ample subsurface water storage in backfilled areas, primarily migrating along the original river path owing to topographical limitations. Although the distribution patterns of soil moisture in each backfilling block varied slightly, the boundaries of soil moisture content and variation mainly appeared at depths of 8 m and 20 m underground. Significant moisture variation occurred across the 0–20 m underground layers, suggesting the 8–20 m layer could function as a groundwater collection zone in the study area. Human activities could disturb groundwater, altering migration pathways from the original river path. An optimized “Drainage–Conveyance–Barrier” system is proposed to enhance GLC sustainability, involving upstream groundwater level control, midstream soil moisture management, and downstream hydrological connectivity improvement. These findings carry substantial implications for guiding the planning and execution of GLC engineering initiatives. The novelty of this study lies in its application of ERT to provide a detailed spatial and temporal understanding of soil moisture dynamics in the GLC areas. Future research should focus on factors such as soil types and topographical changes for a comprehensive assessment of GLC’s impact on small watershed groundwater hydrology.

Enhanced fluoride removal from water using acid-modified red clay soil from the Loess Plateau of China

ABSTRACT The discharge of fluoride-containing wastewater poses a severe threat to global water resources, ecosystems, and human health. Urgently needed are economically feasible and environmentally sustainable solutions for worldwide fluoride contamination. This study explores utilizing unmodified and modified red clay soils from China's Loess Plateau as adsorbents for fluoride mitigation. Sulfuric acid-modified red clay soil showed higher fluoride removal than unmodified, NaOH-modified, and thermally modified soils. Fluoride adsorption decreased with rising pH from 2.0 to 10.0 for unmodified (67.67–3.91%) and acid-modified red clay soil (90.44–32.06%). The Langmuir model better described the data (R2 = 0.9821, 0.9901 for unmodified, acid-modified soil), improving maximum adsorption capacity by 252%. Pseudo-second-order kinetics (R2 = 0.9925, 0.9954 for unmodified, acid-modified soil) accurately described the kinetic data. Acid modification improved reaction rates, shortening the breakpoint from 6.694 to 2.318 min1/2. Over time, the process transitioned from intraparticle diffusion to external mass transfer and intraparticle diffusion. FTIR analysis showed that acid modification strengthened ligand exchange and provided ion exchange opportunities. This study advances fluoride adsorption through innovative clay soil utilization, offering economical, viable, and environmentally friendly solutions.

Feasibility and application of soil reconstruction technology for farmland consolidation in China's Loess Plateau

With the widespread implementation of farmland consolidation projects globally, the poor soil quality of newly created farmland (NCF) has become a significant bottleneck hindering the sustainable progress of such projects. Soil reconstruction technology (SRT), an innovative method to rapidly and effectively enhance the soil quality of NCF, has emerged as a prominent area of research in modern agricultural development. The Loess Plateau in China is highly susceptible to soil erosion and ecological degradation, making it a prime location for large-scale farmland consolidation efforts over the years. Investigating the practical feasibility and application potential of SRT can offer crucial technical insights for project implementation. This study conducted a field experiment in the Yangjuangou catchment of Yan’an City to explore the effects of soil mixing measures on soil properties and crop yield. Results indicated significant improvements in soil particle size distribution, physicochemical properties, and maize yield of NCF following soil reconstruction through the mixing of Malan Loess. Furthermore, the application of SRT demonstrated practical feasibility for farmland consolidation, leading to maximum crop yield and optimal ecological and economic benefits. The study also deliberated on the implications of farmland consolidation for land use policy and its contribution to sustainable agricultural development.

The dimensions of deep-layer soil desiccation and its impact on xylem hydraulic conductivity in dryland tree plantations

Abstract. In water-limited areas, planted trees can extract substantial amounts of soil water from deep layers (> 200 cm) to meet their high water demand, resulting in deep soil desiccation, which influences not only regional water cycling but also the sustainability of trees per se in drylands. However, the specific dimensions of deep soil desiccation in relation to both the soil moisture limitation and the maximum root water uptake (RWU) depth are still not well determined. Whether the dimensions depend on tree species and how they will affect trees' xylem hydraulic conductivity are also unclear, restricting our ability to predict the fate of dryland tree plantations. Therefore, we studied the spatiotemporal distribution of deep soil moisture deficit (DSMD) for two typical planted trees, apple (Malus pumila Mill.) and black locust (Robinia pseudoacacia L.), based on published data and multiple field samplings on China's Loess Plateau. The results indicated that the lowest deep soil moisture (DSM; units of gravimetric percent, i.e., grav-%) occurred under the planted trees aged 24–28 years at all sites. The lowest DSMD varied around −0.6, which was close to the DSMD at the permanent wilting point (PWP, grav-%), regardless of tree species and site, although shallow (< 200 cm) soil moisture was not reduced to the point of limitation. This suggests that PWP is a reliable indicator of the moisture limitation of deep-layer soil desiccation for the tree species examined. The corresponding depth of soil moisture use reached 18.0–22.0 m for these old planted trees at different sites, while it was more than 25 m for R. pseudoacacia in the drier site of Mizhi. Furthermore, the mean values of native percentage loss of hydraulic conductivity of planted trees' branches xylem reached 74.9 %–96.5 % in the plantations sampled in this study, indicating that tree mortality may occur. The findings help predict the sustainability of planted trees in semi-arid regions with a thick vadose zone.

Revisiting the hydrological legacy of revegetation on China's Loess Plateau using Eagleson's ecohydrological perspective

Revegetation has resulted in a trend of increasing vegetation greenness on the Chinese Loess Plateau. However, it remains unclear whether the regional vegetation coverage exceeds hydroclimatic limitations in the context of revegetation, and the hydrological effects of greening are controversial. Eagleson's optimality hypothesis can explain some of the hydrological effects on the Loess Plateau. Here, building on previous research, the geospatial vegetation states were estimated for pre- and post-revegetation periods on the Loess Plateau from 1982 to 2015 using Eagleson's ecological optimality theory. Additionally, a drought composite analysis approach was utilized to investigate the hydrological effects related to drought (including sensitivity and partitioning) under various vegetation states. It was found that revegetation increased the proportion of catchments in the equilibrium state and decreased the proportion in the disturbed state, owing to a wetter climate compared with the pre-revegetation period. Root-zone soil drought, driven by precipitation (P) deficit, asymmetrically triggered hydrological effects for both the pre- and post-revegetation periods, with reduced runoff (Q) for both periods and a decrease in evapotranspiration (ET) during the pre-revegetation period but an increase in ET during the post-revegetation period. Moreover, catchments in an equilibrium state exhibited lower sensitivity between ET and P, and more stable partitioning of ET with regards to P, compared with those in a disturbed state. These results underscore the theoretical framework that an equilibrium state is crucial for maintaining ecosystem ET. Our results highlight the necessity of considering the hydrologic regulation of vegetation states when assessing the hydrological effects of vegetation change.

Assessing rainfall erosivity changes over China through a Bayesian averaged ensemble of high-resolution climate models

Spatiotemporal variation in rainfall erosivity resulting from changes in rainfall characteristics due to climate change has implications for soil erosion in developing countries. To promote soil and water conservation planning, it is essential to understand past and future changes in rainfall erosivity and their implications on a national scale. In this study, we present an approach that uses a Bayesian model averaging (BMA) method to merge multiple regional climate models (RCMs), thereby improving the reliability of climate-induced rainfall erosivity projections. Our multi-climate model and multi-emission scenario approach utilize five RCMs and two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenarios for the baseline period (1986–2005) and future periods (2071–2090) to characterize the spatiotemporal projection of rainfall erosivity and assess variations in China. Our results indicate that the two models outperform other models in reproducing the spatial distribution and annual cycle of rainfall erosivity in China. Moreover, we found an increasing trend in the annual rainfall erosivity from the baseline climate up to the RCMs for all models, with an average change in erosivity of approximately 10.9% and 14.6% under RCP4.5 and RCP8.5, respectively. Our BMA results showed an increase in the absolute value of rainfall erosivity by 463.3 and 677.0 MJ·mm·hm−2·h−1, respectively, in the South China red soil region and the Southwest China karst region under the RCP8.5 scenario. This increase indicates that climate warming will significantly enhance the potential erosion capacity of rainfall in these regions. Additionally, our study revealed that the Southwest China karst region and the Northwest China Loess Plateau region are more sensitive to radiation forcing. To mitigate the risk of soil erosion caused by climate change, it is necessary to consider changes in rainfall erosivity, local soil conditions, vegetation coverage, and other factors in different regions and take appropriate soil and water conservation measures.

Unraveling carbon stock dynamics and their determinants in China's Loess Plateau over the past 40 years

Synergies and trade-offs among land use and land covers (LULCs) pose considerable uncertainties in achieving the dual carbon goals for China's Loess Plateau (CLP). In this context, we unraveled the carbon stock dynamics induced by land use and land cover change (LUCC) in the CLP over the past 40 years using the satellite-derived annual LULC maps and the InVEST model. Then, mixed measures were employed to quantify the global and local responses of the carbon stock dynamics to both natural and anthropogenic factors. We found that approximately a total of 5.58 × 109 Mg of carbon was stored in the CLP's ecosystems in 2019. Chronologically, the total carbon stock showed a slight decrease in the CLP from 1980 to 2019 due to the extensive LUCCs linked to socioeconomic activities. Specifically, the total carbon density loss rate accelerated in urban–rural-wild continuum (RUWC) types with higher human activity intensity, such as villages and urban, while it decelerated in woodlands, and croplands, where the human activity intensity is lower. Moreover, the total carbon density gain rate in wildlands was accelerating. Finally, we revealed that the carbon stock dynamics in the CLP over the past 40 years were primarily influenced by socioeconomic variables and have responded diversely to the drivers in space.

Distinguishing Trajectories and Drivers of Vegetated Ecosystems in China's Loess Plateau

AbstractTerrestrial ecosystems can exhibit various behaviors in response to climate change and human activities. Nonlinear and abrupt shifts in ecosystems are particularly important as they indicate substantial modifications in ecosystem structure and function, posing a threat to the provision of ecosystem services. Here we distinguish between linear, curvilinear, and abrupt shifts in ecosystem productivity from 2000 to 2020 in China's Loess Plateau. We utilize spatial Random Forest models to analyze the driving factors behind these change patterns. Our findings indicate that 84.1% of the ecosystems experienced a positive change in plant productivity, while a small proportion (2.5%) exhibited a negative change. Abrupt shifts are prevalent in both positive and negative changes in ecosystem productivity, with negative changes often manifesting as abrupt shifts (79.3%). Negative changes in plant productivity, particularly the negative abrupt shifts, are primarily associated with human activities characterized by increased nighttime light and urbanization. Land conversion to forest is linked to a curvilinear trajectory in plant productivity, characterized by nonlinear changes with acceleration. Higher water availability and a wetter environment are more likely to promote positive changes in plant productivity. Moderate warming trends contribute to abrupt positive changes in plant productivity, while high warming trends are associated with increased negative abrupt and curvilinear changes. We highlight the importance of accounting for diverse change behaviors in ecosystems for the development of targeted conservation and restoration measures.

Response of microbial communities to the changes in grazing intensity and season in a typical steppe

Livestock grazing is an influencing factor playing a key role in shaping the plant community, microbial community, and soil properties in grassland ecosystems. Northern China's Loess Plateau has been used for livestock grazing for centuries and is a vulnerable ecosystem. In this study, the fates of bacterial and fungal communities of the typical steppe of the Loess Plateau were investigated under increasing grazing intensities practiced in summer and winter seasons. The results revealed changes in soil physiochemical properties, plant community properties, and microbial diversity in response to alterations in the grazing intensity. The alpha diversity of microbial communities (including bacteria and fungi) exhibited an uneven trend during summer grazing due to an increase in grazing intensity, but it decreased during winter grazing; however, the observed changes were not significant. The beta diversity of the bacterial community was highly influenced by grazing intensity, the summer community clustered near nongrazing, and the winter community presented significantly different results. The beta diversity of the fungal community was not influenced by grazing intensity or season. Grazing induced the growth of fast-growing bacteria (such as Actinobacteria and Firmicutes) and saprophytic fungi and a reduction in overall pathogenic traits. Co-occurrence network analysis and a structural equation model revealed changes in soil and plant properties (such as soil nitrogen level, soil organic carbon level, aboveground biomass, and litter biomass), with an increase in grazing intensity contributing to alterations in bacterial and fungal diversities. This finding demonstrates that grazing intensity can directly affect soil microbes and play an indirect role by modifying soil nutrients and reducing plant biomass, which eventually contributes to changes in microbial communities. Overall, implementing low grazing intensity is suggested for maintaining the microbial community structure the same as that of the native microbiome (ungrazed) in the steppe ecosystems.

Plants extend root deeper rather than increase root biomass triggered by critical age and soil water depletion

Exploring plant root characteristics is important to understand the aboveground plant growth and ecosystem, but has rarely been conducted because of the difficulties in obtaining root information. This study aims to clarify the root distribution and rooting strategy under the combined control of vegetation types and rainfall gradients. We compiled 64 plant root and 81 soil water profiles up to 10 m deep with plant ages of up to 40 years old in China's Loess Plateau, and then fitted the shape and extinction coefficients (β) and proposed the relation of D95/D50 (ratio of depth corresponding to 95 % of total biomass to that corresponding to 50 % of total biomass) to β to characterize the rooting strategy. The cumulative root biomass increase from shallow- to deep-rooted plants, and from >550 mm to <450 mm precipitation gradients. The root system parameters have large spatial variability, dominated by vegetation type but supplemented by climate. The negative correlation between D95/D50 and β indicated a tradeoff between rooting depths and root biomass. The plants would change rooting strategy from increasing root biomass to increasing rooting depths when the plant stand age and soil water depletion degree are >25.7 ± 3.6 years and 35.7 % ± 15.1 %, respectively. These results reveal a clear plant rooting strategy that extends root deeper rather than increases root biomass triggered by critical age and soil water depletion.

Disturbance reduces the moss‐dominated biocrust inhibition on infiltration and improves soil moisture storage within the Loess Plateau, China

Various factors influence biocrust effects on infiltration and soil moisture. On China's Loess Plateau, well‐developed moss‐dominated biocrusts reduce infiltration and suppress shrub growth, however, the interrelationships between rainfall conditions and disturbance management to alleviate these impacts are unknown. In a semiarid watershed on the Loess Plateau, we applied two forms of disturbance, scarification (controlled harrowing) and compaction (simulated grazing), at four intensity levels (control‐intact, light, moderate, and heavy) to well‐developed moss‐dominated biocrusts and a bare soil (BS) for comparisons to form eight treatments with three replications. Rainfall intensity and depth, soil moisture, run‐off, and sediment yield were measured during the rainy season (July–October). In total, well‐developed biocrusts did not significantly affect infiltration but reduced soil moisture at depths of 120–180 cm (p &lt; 0.05), and disturbance increased infiltration and deep soil moisture beneath biocrusts (p &lt; 0.05). Rainfall conditions changed the effects of biocrusts and disturbance. Under long, low‐intensity rainfall, moss‐dominated biocrust infiltration was slightly greater than BS, but scarification increased infiltration and compaction reduced it (p &lt; 0.001). Under short, high‐intensity rainfall, biocrusts reduced infiltration, and disturbance intensity increased infiltration and sediment yields (p &lt; 0.001). Light grazing or using light or moderate scarification improves well‐developed moss‐dominated biocrust infiltration in the pastures during May–June before the rainy season during July–October on the Loess Plateau, while avoiding increased soil erosion.