Frequent periods of drought conditions are known to limit plant performance, primary production, and ecosystem stability in arid and semi-arid desert steppe environments. Plants often avoid competition by shifting their water use seasonally, which affects the water-use patterns of dominant species as well as the composition and structure of plant communities. However, the water-use strategies of dominant herbaceous species, which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region, China, are poorly known. Here, we explored the possible sources of water uptake and water-use efficiency (WUE) of three dominant herbaceous plant species (Stipa breviflora, Agropyron mongolicum, and Glycyrrhiza uralensis) in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters, including (1) the stable isotopic oxygen and hydrogen (δ ¹⁸O and δ ²H) compositions of precipitation, soil water, and stem water, (2) the carbon isotope ( ¹³C) composition of leaves, and (3) the soil water contents, based on field sampling across varying water conditions from June to September, 2017. Frequent small precipitation events replenished shallow soil water, whereas large events only percolated down to the deep soil layers. Changes in soil water availability affected the water-use patterns of plants. Generally, during light precipitation periods, the deep root system of G. uralensis accessed deeper (>80 cm) soil water, whereas S. breviflora and A. mongolicum, which only have shallow roots, primarily absorbed water from the shallow and middle soil layers. As precipitation increased, all three plant species primarily obtained water from the shallow soil layers. Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water. In addition, the δ ¹³C values of G. uralensis and S. breviflora were higher than those of A. mongolicum. The δ ¹³C values of the three plant species were significantly negatively correlated with soil water content. Therefore, G. uralensis and S. breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season. In contrast, A. mongolicum, with a relatively low WUE in the wet season but a high WUE in the dry season, exhibited a more flexible water-use strategy. The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.

Investigating the relationships between vegetation dynamic and edaphic factors provide management insights into factors affecting the growth and establishment of plant species and vegetation communities in saline areas. The aim of this study was to assess the spatial variability of various vegetation communities in relation to edaphic factors in the Great Salt Desert, central Iran. Fifteen vegetation communities were identified using the physiognomy-floristic method. Coverage and density of vegetation communities were determined using the transect plot method. Forty soil samples were collected from major horizons of fifteen profiles in vegetation communities, and analyzed in terms of following soil physical and chemical characteristics: soil texture, soluble Na ⁺ concentration, sodium adsorption ratio (SAR), electrical conductivity (EC), pH, organic matter content, soluble Mg ²⁺ and Ca ²⁺ concentrations, carbonate and gypsum contents, and spontaneously- and mechanically-dispersible clay contents. Redundancy analysis was used to investigate the relationships between vegetation dynamic and edaphic factors. The generalized linear method (GLM) was used to find the plant species response curves against edaphic factors. Results showed that plant species responded differently to edaphic factors, in which soluble sodium concentration, EC, SAR, gypsum content and soil texture were identified as the most discriminative edaphic factors. The studied plant species were also found to have different ecological requirements and tolerance to edaphic factors, in which Tamarix aphylla and Halocnemum strobilaceum were identified as the most salt-resistant species in the region. Furthermore, the presence of Artemisia sieberi was highly related to soil sand and gypsum contents. The results implied that exploring the plant species response curves against edaphic factors can assist managers to lay out more appropriate restoration plans in similar arid areas.

Understanding the spatiotemporal patterns of the forage-livestock balance is imperative for regionally arranging animal husbandry production while ensuring sustainable grassland-ecosystem service use. The Xilin Gol steppe is an important native grassland resource in Inner Mongolia Autonomous Region, China. This study aimed to elucidate the dynamics of the forage-livestock balance in the Xilin Gol steppe during the period 2000-2015. We evaluated the forage production and corresponding livestock carrying capacity (LCC) in the growing seasons of 2000-2015 using remote sensing data and field surveys. The spatiotemporal patterns of the forage-livestock balance were then assessed at regional, city (including city, county and banner), and village scales using statistical and household survey data. The results showed that both forage production and LCC decreased in the Xilin Gol steppe from east to west. During the period 2000-2015, the regional average forage production and corresponding LCC fluctuated without following a distinct trend, but were consistent with the variations in precipitation. The forage-livestock balance varied with time, space, and scale. At the regional scale, steppes were overgrazed in the early 2000s, but a forage-livestock balance or even grazing potential was achieved in other years. At the city scale, approximately half of the region exhibited a "forage-livestock balance" since 2000. However, about half of the region still experienced overgrazing, which mainly located in the southwest sandy zones. Such changes may have been affected by the variations in grassland quality, forage production, compensation payment, and so on. We suggest a location-specific management scheme for grazing constraints, ecological compensation payment, and industry development to aid in harmonizing animal husbandry and environmental restoration, while promoting sustainable development goals by 2030.

Crop residue is a major source of soil organic matter; therefore, application of crop straw to soil contributes to the sustainable development of organic agriculture. To better understand the transformation of crop straw in orchard soils, we investigated the relationship between the characteristics of straw decomposition and functional diversity of associated microbial communities in a long-term peach orchard, China. Mesh bags, each containing 30 g of corn or bean straw, were buried at a soil depth of 20 cm in a 12-year-old peach orchard for 360 d (October 2011-October 2012). Three treatments were applied, i.e., fresh corn straw, fresh corn straw with nitrogen fertilizer (urea, 10.34 g/kg), and fresh bean straw. Changes in straw residual rate, straw water content and soil conditions were monitored after treatment. The functional diversity of straw-associated microbial communities was analyzed by the Biolog-Eco microplate assay. During the decomposition process, straw residual rates did not vary considerably from 10 d (30.4%-45.4%) to 360 d (19.0%-30.3%). Irrespective of nitrogen addition, corn straw decomposed faster than bean straw. Corn straw with nitrogen fertilizer yielded the highest average well color development (AWCD) values (1.11-1.67), followed by corn straw (1.14-1.68) and bean straw (1.18-1.62). Although the AWCD values did not differ significantly among the three treatments, substantial differences occurred across various time periods of the decomposition process (P<0.01). In terms of carbon source utilization, the dominant microbial groups fed mainly on saccharides. Hard-to-decompose substances gradually accumulated in the middle and late stages of straw decomposition. Of the six categories of carbon sources tested, the utilization rate of aromatics was the lowest with corn straw, whereas that of polymers was the lowest with bean straw. Among different treatments, straw residual rate was negatively correlated to soil available phosphorous, soil available potassium and soil temperature (P<0.05), but not to soil water content. In some cases (corn straw with or without nitrogen fertilizer), straw residual rate was negatively correlated to straw water content, amino acid utilization and carboxylic acid utilization, and positively correlated with microbial species richness and evenness (P<0.05). Microbial community associated with corn and bean straw decomposition in soil was respectively dominated by aromatic- and polymer-metabolizing groups during the middle and late stages of this process, which could reduce the stability of microbial community structure and decrease the rate of straw decomposition in the fruit tree orchard.

The distribution of binding agents (i.e., soil organic carbon (SOC) and glomalin-related soil protein (GRSP)) in soil aggregates was influenced by many factors, such as plant characteristics and soil properties. However, how these factors affect binding agents and soil aggregate stability along a climatic gradient remained unclear. We selected the Robinia pseudoacacia L. forests from semi-arid to semi-humid of the Loess Plateau, China to analyze the plant biomass, soil physical-chemical properties, SOC and GRSP distribution in different sized soil aggregates. We found that from semi-arid to semi-humid forests: (1) the proportion of macro-aggregates (>0.250 mm) significantly increased (P<0.05), whereas those of micro-aggregates (0.250-0.053 mm) and fine materials (<0.053 mm) decreased and soil aggregate stability was increased; (2) the contents of SOC and GRSP in macro-aggregates and micro-aggregates significantly increased, and those in fine materials decreased; (3) the contribution of SOC to soil aggregate stability was greater than those of total GRSP and easily extractable GRSP; (4) soil properties had greater influence on binding agents than plant biomass; and (5) soil aggregate stability was enhanced by increasing the contents of SOC and GRSP in macro-aggregates and soil property was the important part during this process. Climate change from semi-arid to semi-humid forests is important factor for soil structure formation because of its positive effect on soil aggregates.

The Karakoram Mountains are well known for their widespread surge-type glaciers and slight glacier mass gains. On the one hand, glaciers are one of the sensitive indicators of climate change, their area and thickness will adjust with climate change. On the other hand, glaciers provide freshwater resources for agricultural irrigation and hydroelectric generation in the downstream areas of the Shaksgam River Basin (SRB) in western China. The shrinkage of glaciers caused by climate change can significantly affect the security and sustainable development of regional water resources. In this study, we analyzed the changes in glacier area from 2000 to 2016 in the SRB using Landsat TM (Thematic Mapper)/ETM+ (Enhanced Mapper Plus)/OLI (Operational Land Imager) images. It is shown that the SRB contained 472 glaciers, with an area of 1840.3 km ², in 2016. The glacier area decreased by 0.14%/a since 2000, and the shrinkage of glacier in the southeast, east and south directions were the most, while the northeast, north directions were the least. Debris-covered area accounted for 8.0% of the total glacier area. We estimated elevation and mass changes using the 1 arc-second SRTM (Shuttle Radar Topography Mission) DEM (Digital Elevation Model) (2000) and the resolution of 8 m HMA (High Mountain Asia) DEM (2016). An average thickness of 0.08 (±0.03) m/a, or a slight mass increase of 0.06 (±0.02) m w.e./a has been obtained since 2000. We found thinning was significantly lesser on the clean ice than the debris-covered ice. In addition, the elevation of glacier surface is spatially heterogeneous, showing that the accumulation of mass is dominant in high altitude regions, and the main mass loss is in low altitude regions, excluding the surge-type glacier. For surge-type glaciers, the mass may transfer from the reservoir to the receiving area rapidly when surges, then resulting in an advance of glacier terminus. The main surge mechanism is still unclear, it is worth noting that the surge did not increase the glacier mass in this study.

Actual evapotranspiration (ET_a) is a key component of water balance. This study aimed to investigate the spatial variability and time stability of ET_a along a hillslope and to analyze the key factors that control the spatiotemporal variability of ET_a. The potential evaporation, surface runoff and 0-480 cm soil water profile were measured along a 243 m long transect on a hillslope of the Loess Plateau during the normal (2015) and wet (2016) water years. ET_a was calculated using water balance equation. Results indicated that increasing precipitation during the wet water year did not alter the spatial pattern of ET_a along the hillslope; time stability analysis showed that a location with high time stability of ET_a could be used to estimate the mean ET_a of the hillslope. Time stability of ET_a was positively correlated with elevation (P<0.05), indicating that, on a hillslope in a semi-arid area, elevation was the primary factor influencing the time stability of ET_a.