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Land-use change is supposed to exert significant effects on the spatio-temporal patterns of ecosystem carbon storage in arid regions, while the relative size of land-use change effect under future environmental change conditions is still less quantified. In this study, we combined a land-use change dataset with a satellite-based high-resolution biomass and soil organic carbon dataset to determine the role of land-use change in affecting ecosystem carbon storage from 1980 to 2050 in the Gansu province of China, using the MCE-CA-Markov and InVEST models. In addition, to quantify the relative size of the land-use change effect in comparison with other environmental drivers, we also considered the effects of climate change, CO2 enrichment, and cropland and forest managements in the models. The results show that the ecosystem carbon storage in the Gansu province increased by 208.9 ± 99.85 Tg C from 1980 to 2020, 12.87% of which was caused by land-use change, and the rest was caused by climate change, CO2 enrichment, and ecosystem managements. The land-use change-induced carbon sequestration was mainly associated with the land-use category conversion from farmland to grassland as well as from saline land and desert to farmland, driven by the grain-for-green projects in the Loess Plateau and oasis cultivation in the Hexi Corridor. Furthermore, it was projected that ecosystem carbon storage in the Gansu province from 2020 to 2050 will change from −14.69 ± 12.28 Tg C to 57.83 ± 53.42 Tg C (from 105.62 ± 51.83 Tg C to 177.03 ± 94.1 Tg C) for the natural development (ecological protection) scenario. By contrast, the land-use change was supposed to individually increase the carbon storage by 56.46 ± 9.82 (165.84 ± 40.06 Tg C) under the natural development (ecological protection) scenario, respectively. Our results highlight the importance of ecological protection and restoration in enhancing ecosystem carbon storage for arid regions, especially under future climate change conditions. [ABSTRACT FROM AUTHOR]

Salinization is considered a significant threat to soil ecosystem and plant growth in arid and semiarid regions. Soil microorganisms are supposed to be essential in relieving soil salinization and enhancing plant salt tolerance. However, although the responses of soil fungal diversity and community structure to salt stress have been investigated, major knowledge gaps remain in the interactions and community assembly of abundant and rare fungal taxa, and fungal functional characteristics under different salt intensities. Here, next-generation sequencing technology were used to investigate the response of all, abundant and rare fungal taxa to salt stress in arid and semiarid regions. The results demonstrated that high salt stress reduced the complexity and stability of fungal networks and increased fungal collaborations. Rare taxa held a key position in the co-occurrence network and exhibited greater proficiency in collaborating with intermediate and rare taxa, thereby augmenting the resistance of the community and maintaining its stability. Notably, with increasing salt stress, the importance of rare taxa gradually enhanced, while the importance of abundant taxa decreased. Moreover, fungal communities were manipulated by stochastic processes under salt stress, while were also influenced by deterministic processes (heterogeneous selection), especially for rare taxa. Furthermore, low salinity conditions promoted the colonization of saprophytic and symbiotic fungi and inhibited the growth of pathogenic fungi. Functional groups associated with fungal parasite-soil saprotroph-undefined saprotroph function were extremely sensitive to soil salinity and exerted a pivotal influence in sustaining community stability. Our findings may broaden our understanding of how abundant and rare fungi react to salt stress, making it easier to forecast the possible loss of biodiversity due to soil salinization, and offering microbial references for the development of saline-alkaline soil. [Display omitted] • Fungal networks were less stable but more collaborative under salt stress. • Rare taxa were more robust in sustaining community stability than abundant taxa. • Rich and rare taxa's importance gap in sustaining network increased as salinity rose. • Stochastic processes gradually dominated community assembly as salinity increased. • Heterogeneous selection contributed more to rare taxa assembly than to abundant taxa. [ABSTRACT FROM AUTHOR]

• The hydrology changes is sensitive to energy in high-altitude. • The hydrology changes is controlled by water limitation in low-altitude area. • The water-energy coupling relation highly relies on altitudinal gradient. • Climate change dominate the hydrological shifts in alpine region. Hydrology heterogeneity refers to the different water regimes or hydrological processes in response to heterogeneous in topography, landscapes, land cover, soil properties, geology and meteorology reflecting as the spatial variation of precipitation, evapotranspiration and water yield along with landscape, elevation, terrain and climate variation. However, the hydrology heterogeneity in the alpine region of inland river basin has remained unclear to date, which limits the understanding of the hydrology and landscape interaction mechanism and affects the rational utilization of regional water resources. In this study, we combined the soil and water assessment tool (SWAT) and water-energy coupling framework to detect the hydrology heterogeneity in the arid alpine region of Heihe River Basin (HRB). We applied SWAT model to present the hydrological processes and regimes at different landscapes and elevation bands by using field measured parameters, and investigate the hydrology heterogeneity as well as the response to the changes in recent climate and land surface in the perspective of water-energy coupling framework. The results indicate that SWAT is indeed a robust tool in representing the streamflow process in alpine region with accurate performance. The distribution of landscapes reflect the comprehensive effect of regional water-energy coupling, which highly rely on the altitudinal gradient. The hydrology heterogeneity in high-altitude area is sensitive to energy and in low-altitude area is sensitive to water limitation (drought stress). Climate change is the dominate factor that driving the hydrology heterogeneity shifts in alpine region of HRB, while, the effect of land surface change is gradually strengthening over the past 50 years, reflecting with the contribution of land surface change on hydrology shifts is gradually increasing. [ABSTRACT FROM AUTHOR]

The nitrate pollution of groundwater in arid areas subject to human activity, and especially agricultural activity, is of immense environmental concern. Groundwater is the main water source in arid areas, once an aquifer is polluted, the impact upon the security of the water supply becomes all the more serious. The process of nitrate transformation is also different from that of humid areas, therefore, it is very important to identify and quantify the nitrate sources in aquifers. Using the hydrochemical, stable isotope tracers of 194 groundwater samples, and combining these with the MixSIAR model, the spatial distribution of groundwater nitrates in the Shiyang River Basin (SRB), China, was mapped. The relative contributions made by nitrate sources to different aquifers, and their key transformation processes, were identified. It was found that, shallow groundwater is seriously polluted, with NO 3 − concentrations ranging from 1.1 to 438.7 mg L−1. In the SRB, NO 3 − concentrations of 23% and 73% in shallow groundwater samples exceed the NO 3 − concentration limits found in natural sources (13.3 mg L−1), and the World Health Organization (WHO) nitrate limits for drinking water (50 mg L−1). Furthermore, the nitrates found in confined aquifers indicate that these are also affected by anthropogenic sources, with concentrations ranging from 1.6 to 44.7 mg L−1. Soil organic nitrogen (51.9%) and NH 4 + fertilizer (20.8%), wastewater and manure (20.5%) are the main sources of groundwater nitrates; NO 3 − fertilizer (4.4%) and precipitation (2.3%) have a relatively insignificant effect on groundwater nitrates. The process of nitrification is the main factor affecting changes in nitrate concentrations in aquifers. Other than the denitrification observed in the shallow aquifers of the Minqin Basin (MQB), there was no significant denitrification in the other sub-basins of the SRB. Anthropogenic sources, especially agricultural sources, are now major contributors to the increases in groundwater nitrate concentrations observed in the SRB. This study provides data that can be used to help prevent groundwater pollution and enhance water resources management in arid areas. [Display omitted] • Except Jinchang sub-basin, nitrate pollution in groundwater is obvious in other sub-basins of SRB. • Nitrate concentrations in confined aquifer have also been affected by anthropogenic sources. • The process of nitrification is the main factor affecting changes in nitrate concentrations in aquifers. • A denitrification process that would alleviate the nitrate pollution of groundwater bodies is relatively lacking in SRB. [ABSTRACT FROM AUTHOR]