A fundamental challenge in soil macroecology is to understand how microbial community structure shapes ecosystem function along environmental gradients of the land surface at broad spatial scales (i.e. the horizontal dimension). However, little is known about microbial community structure–function relationships in extreme environments along environmental gradients of soil depth at finer spatial scales (i.e. the vertical dimension). Here, we propose a general spatial dimension partitioning approach for assessing the patterns and drivers of soil microbial community structure–function relationships across horizontal and vertical spatial gradients simultaneously. We leveraged a 200‐km desert soil salinity gradient created by a 12‐year saline‐water irrigation in the Tarim basin of Taklamakan Desert. Specifically, using a general linear model, hierarchical variance partitioning, and a path model, we assessed the patterns and key ecological processes controlling spatial turnover in microbial community structure (i.e. β‐diversity) and enzymatic activity relevant to carbon, nitrogen, and phosphorus cycling along soil salinity gradients across study sites (horizontal dimension) and soil depths (vertical dimension). We found a decoupled relationship between soil microbial β‐diversity and enzymatic activity. Differences in soil depth (on the scale of meters) were as important as geographic distance (on the scale of kilometers) in shaping bacterial and fungal β‐diversity. However, the vertical and horizontal turnover in enzymatic activity was largely attributed to an increase in the heterogeneity of soil properties, such as soil texture, water content, and pH. Our findings suggest that dispersal limitation controls microbial community β‐diversity and that environmental heterogeneity, rather than soil salinization, controls enzymatic activity. Taken together, this work highlights that in the face of ongoing environmental alterations, soil depth is an under‐explored spatial dimension that must be considered in soil conservation efforts as a critical factor in determining microbial community structure and function in extreme environments.

Soil bacteria, the predominant microbiota in soil, are subject to the law of minimum and the law of tolerance, but the assembly patterns of soil bacteria in response to environmental factors remain far from clear. Here, we took advantage of an altitudinal gradient (1020–1770 asl) in oak-dominant forests and assessed whether soil bacteria linearly or nonlinearly respond to environmental properties through the changes in the community diversity and composition. We found that soil bacteria decreased with increasing altitude in terms of the species richness and phylogenetic structure, while they were unchanged with increasing altitude in terms of community composition. The species richness was nonlinearly affected by the soil pH (19.9%), C:N ratio (14.3%), SOC (11.4%), and silt + clay content (9.9%). Specifically, the species richness peaked at a pH of 5.5–6.5, and an SOC of 25–50 g kg⁻¹, and it showed abrupt decreases and increases at a C:N ratio of 14.5 and a silt + clay content of 70%. The community composition was significantly affected by the soil pH (28.2%), then by the SOC (3.6%), available phosphorus (1.0%), and silt + clay content (0.5%), and it showed less turnovers at a pH of 6.0, SOC of 50 g kg⁻¹, and available phosphorus > 3.0 g kg⁻¹. These findings imply that environmental filtering processes nonlinearly shape bacterial communities.

Nitrogen (N) deposition and grazing (G) are two disturbances of grassland ecosystems and these can greatly affect soil respiration. To date, few studies have investigated this topic in sandy grasslands. Here, we conducted a manipulative experiment in a sandy grassland in Inner Mongolia, China in the year 2013 and 2014, to investigate the effects of N addition and grazing on soil respiration. The results showed that N addition significantly accelerated soil respiration in both 2013 and 2014. The respiration enhancement under N addition varied during the growing season, being larger in early May 2014 (0.40 μmol·m⁻²·s⁻¹) and early July 2014 (1.29 μmol·m⁻²·s⁻¹) than in October 2014 (0.03 μmol·m⁻²·s⁻¹). Grazing plots yielded a lower cumulative soil respiration rate than the control plots (−5,68% in 2013 and −1.07% in 2014), although the difference was not significant. In this study, soil temperature rather than soil moisture was the main factor affecting the temporal variation in soil respiration during the growing season. The inter-plot analysis showed that the soil ammonium nitrogen (NH₄⁺–N) content, C:N ratio, and root biomass were significantly correlated with soil respiration, indicating that soil respiration under N-addition or grazing treatment could be affected by changing soil microhabitat conditions, thus affecting soil respiration.

SCIEPublish is an international open-access journal publishing service provider run by SCIE Publishing Limited, dedicated to supporting and inspiring scientists or institutions/societies who aspire to publish high-quality journals.

Fungal communities, typically K-strategy, demonstrate significant potential to counteract environmental stresses. Theories of complexity- and biodiversity-stability suggest that ecosystem stability may be differentially influenced by common species, which engage in intense interactions, and rare species, which contribute to diversity. Here, taking advantage of −0.6 °C/100 m lapse rate, an altitudinal gradient in the Yan-Taihang Mountain Ecological Conservation Area was established, aiming to investigate the responses of common and rare fungi to climatic, plant, and edaphic variations and their potential roles in maintaining stability among low, mid, and high altitudes. Results showed that community composition, rather than diversity, was significantly influenced by altitude, with the abundance of symbiotrophs peaking at mid-altitudes and Saprotrophs at high altitudes. Rare fungi were less accounted for by environmental variables in terms of community composition, whereas their diversity was more sensitive to pH, total phosphorus, and electrical conductivity than the common fungi, indicating that rare species may serve as a resilient gene reservoir under environmental perturbations. The stability of fungal community was further enhanced through interactions among common fungi, with these interactions being slightly compartmentalized and tending more negative at mid (modularity = 0.73, negative-to-positive associations = 0.69%) and high altitudes (modularity = 0.77, negative-to-positive associations = 0.61%) compared with low altitudes (modularity = 0.67, negative-to-positive associations = 0.13%). These results highlighted distinct assembly strategies between common and rare fungi and underscored the importance of common fungi for the persistence of ecological functional zones amidst climate change.

The capacity to develop resilience to global change, such as nitrogen deposition, is an important topic for the management of key ecological functional zones. In this study, nitrogen enrichment (10 g N m⁻² yr⁻¹, NE) and control plots (0 g N m⁻² yr⁻¹, CL), each with eight replications, were randomly established in the Horqin Sandy Land to investigate how grassland carbon sequestration functions and herdsmen’s livelihoods respond to nitrogen deposition. In addition, three grazing scenarios (non-grazing, light grazing, and moderate grazing) were simulated to determine whether human activities affect the relationships (trade-off vs. synergistic) among forage supply, carbon sequestration, and windbreak and sand-fixing services under nitrogen deposition. The results showed that NE exhibited a significant increase in aboveground carbon storage (99.40 g C m⁻², 117.34%) and the shoot carbon/root carbon ratio (1.90) when compared to the CL (0.95) (p < 0.05). NE significantly decreased soil carbon storage ability, particularly in the 10–30 cm soil layer (p < 0.05). The reduction in soil carbon storage was offset by increases in plant carbon storage, resulting in a neutral effect of the NE treatment on the total grassland carbon storage (p > 0.05). The synergistic effects of NE on grassland forage supply and windbreak and sand-fixing functions were observed under a light grazing scenario, which balanced ecological safety and livelihood more effectively than the non-grazing and moderate grazing scenarios. These findings indicate that the structure of grassland carbon storage is influenced by nitrogen deposition and that light grazing would enhance ecosystem services and promote sustainable grassland development.