Desert Grassland Ecosystem Research Articles

The relationships between structure and function of plant communities in the desert steppe

BackgroundAssessing the relationships between spatial and temporal structures and functions of plant communities is an effective way to understand the changing dynamics of plant communities in specific environments. In this study, we investigated the response of structural and functional stabilities of plant communities to stocking rate in the desert steppe over a 16-year grazing period as the research background.MethodsWe used classical statistical methods to investigate the quantitative characteristics of plant communities over time (2014–2019) and space (2017–2019) at four stocking rates (control, CK, 0 sheep·ha–1·month–1; light grazing, LG, 0.15 sheep·ha–1·month–1; moderate grazing, MG, 0.30 sheep·ha–1·month–1; heavy grazing, HG, 0.45 sheep·ha–1·month–1) in the Stipa breviflora desert steppe of Inner Mongolia. We then examined the relationship between structural and functional stability of plant communities.ResultsOn the spatial scale, the structural stability of plant community was the highest in the LG treatment and the lowest in the MG treatment. The functional stability of plant community was the highest in the MG treatment and the lowest in the HG treatment. On the temporal scale, the structural stability of plant community was the highest in the MG treatment and the lowest in the LG treatment. The functional stability of plant community was the highest in the LG treatment and the lowest in the HG treatment. Affected by the stocking rate, the structural stability of plant community fluctuated more widely on the spatial scale and its functional stability varied more widely on the temporal scale. Nonetheless, the functional stability of the plant community is more responsive to the stocking rate.ConclusionsOur findings suggest that influenced by the disturbance of stocking rate, the structural stability of plant community is more significant than the functional stability in the desert grassland ecosystem, which lays a solid foundation for the study of ecosystem stability.

A better simulation of water and carbon fluxes in a typical desert grassland ecosystem through the Common Land Model

How to improve the accuracy and fit-for-purpose of Land surface models (LSMs) in simulating carbon and water fluxes in arid regions, is still a great challenge, since the latent heat flux and terrestrial respiration are underestimated. In this study, we first modified the root water uptake, soil respiration, and stomatal conductance processes and introduced a Bayesian parameter optimization algorithm to optimize the newly introduced fitting parameters. Then, the performance of the calibrated model was evaluated by using eddy covariance observations at a typical desert grassland station. The results showed that the modified soil respiration model better captures the seasonal pattern of terrestrial ecosystem respiration (TER), with the distance between simulated and observed indices (DISO) value decreased from 1.45 to 0.95. Additionally, modifying the root water uptake process can noticeably enhance the simulation of water flux (i.e., latent heat flux) with DISO value decreased from 1.43 to 1.28, but uncertainties remain in simulating carbon flux (i.e., gross primary productivity). Through evaluating three stomatal conductance models under different levels of water stress, we found that both Ball-Woodrow-Berry (BWB) and Ball-Berry-Leuning (BBL) models could improve the CoLM performance in simulating carbon and water fluxes due to their effective response to the water stress with DISO values decreased from 1.96 to 1.68 and 1.67, respectively, while the Unified Stomatal Optimization (USO) model has a relatively poor simulation performance, which fails to capture the impact of water stress with DISO value increased to 2.13. Our study provides valuable insights for improving the simulations of carbon and water fluxes in arid regions by using CoLM.

A late Pleistocene nest cave of Gymnogyps californianus (California Condor) in Texas: New radiocarbon and stable isotope analyses

ABSTRACT Fossil remains of Gymnogyps californianus (California Condor) from Mule Ears Peak Cave, Big Bend National Park, Texas, recovered in the 1930s were reexamined to determine a precise age for nesting condors in this region. Bones of at least 6 prefledged chicks account for most (15, or 65%) of the 23 skeletal elements from this cave and a new osteology collection of known-age condor chicks at the U.S. National Museum, Division of Birds, now allows accurate estimate of the age of death of these fossil condor chicks based on their bone development and porosity. Current and previous radiocarbon dates on juvenile and adult bones, respectively, indicate the presence of condors at this site beginning at ~15,000 calendar years before present (cal yrs BP), with definite nesting occurring at ~13,000 cal yrs BP. Stable isotope analysis (δ13C and δ15N) of bone collagen on 2 bones of adult condors reflects a diet similar to other fossil condors previously analyzed from the inland western U.S. The δ13C values in the Mule Ears Peak condors indicate a diet of megafauna that subsisted on C4 plants in a desert grassland ecosystem. These results support the hypothesis that condors were extirpated from the inland west with the loss of megafauna at the end of the Pleistocene. Further, Big Bend National Park with its vast open space and cliffs and canyons for nesting condors should be considered as an additional release site for captive-reared condors as part of the current Condor Recovery Program.

A dataset of monthly litter recovery from the desert grassland in Southern Tarim Basin during 2010–2020

The Cele National Field Science Observation and Research Station of Desert Grassland Ecosystem of Xinjiang of Chinese Academy of Science (Hereinafter referred to as "Cele Station"), is located on the southern margin of the Tarim Basin bordered to the south by the Kunlun Mountains and to the north by the largest desert in China, the Taklimakan Desert. As a result of simple vegetation community and slow accumulation of soil organic matter, litter serves as an important source of nutrients in this area. Based on the long-term observations of desert plant communities at Cele station, we gathered monthly dynamic data of litter recovery in the desert grassland from Southern Tarim Basin from 2010 to 2020. Based on plant organs (branches, leaves, and fruits), the monthly dynamic data of litter recovery at the observation sites and plots were sorted out, and the annual changes of community and soil nutrients were recorded. Data were compiled in strict accordance with CERN bio-observation specifications. The data has undergone review and quality control by the quality control personnel of the station and sub-center. The results would provide basic data for further study of litter dynamics in the desert grassland from Southern Tarim Basin, and theoretical support for better understanding and assessing nutrient cycling in hyper–arid desert ecosystems.

Effects of acid mine drainage and sediment contamination on soil bacterial communities, interaction patterns, and functions in alkaline desert grassland

Acid mine drainage and sediments (AMD-Sed) contamination pose serious ecological and environmental problems. This study investigated the geochemical parameters and bacterial communities in the sediment layer (A) and buried soil layer (B) of desert grassland contaminated with AMD-Sed and compared them to an uncontaminated control soil layer (CK). The results showed that soil pH was significantly lower and iron, sulfur, and electroconductivity levels were significantly higher in the B layer compared to CK. A and B were dominated by Proteobacteria and Actinobacteriota, while CK was dominated by Firmicutes and Bacteroidota. The pH, Fe, S, and potentially toxic elements (PTEs) gradients were key influences on bacterial community variability, with AMD contamination characterization factors (pH, Fe, and S) explaining 48.6 % of bacterial community variation. A bacterial co-occurrence network analysis showed that AMD-Sed contamination significantly affected topological properties, reduced network complexity and stability, and increased the vulnerability of desert grassland soil ecosystems. In addition, AMD-Sed contamination reduced C/N-cycle functioning in B, but increased S-cycle functioning. The results highlight the effects of AMD-Sed contamination on soil bacterial communities and ecological functions in desert grassland and provide a reference basis for the management and restoration of desert grassland ecosystems in their later stages.

Biological response to Przewalski’s horse reintroduction in native desert grasslands: a case study on the spatial analysis of ticks

BackgroundReintroduction represents an effective strategy for the conservation of endangered wildlife, yet it might inadvertently impact the native ecosystems. This investigation assesses the impact of reintroducing endangered Przewalski's horses into the desert grassland ecosystem of the Kalamaili Nature Reserve (KNR), particularly its effect on the spatial distribution of ticks. In a 25 km2 core area of Przewalski's horse distribution, we set up 441 tick sampling sites across diverse habitats, including water sources, donkey trails, and grasslands, recording horse feces and characteristics to analyze the occurrence rate of ticks. Additionally, we gathered the data of 669 fresh feces of horses. To evaluate the spatial dynamics between these feces and ticks, we used methods such as Fixed Kernel Estimation (FKE), Moran’s I spatial autocorrelation index, and Generalized Linear Models (GLM).ResultsThe dominant species of ticks collected in the core area were adult Hyalomma asiaticum (91.36%). Their occurrence rate was higher near donkey trails (65.99%) and water sources (55.81%), particularly in areas with the fresh feces of Przewalski's horses. The ticks’ three risk areas, as defined by FKE, showed significant overlap and positive correlation with the distribution of Przewalski's horses, with respective overlap rates being 90.25% in high risk, 33.79% in medium risk, and 23.09% in low risk areas. Moran's I analysis revealed a clustering trend of the fresh feces of Przewalski's horses in these areas. The GLM confirmed a positive correlation between the distribution of H. asiaticum and the presence of horse fresh feces, alongside a negative correlation with the proximity to water sources and donkey trails.ConclusionsThis study reveals the strong spatial correlation between Przewalski's horses and H. asiaticum in desert grasslands, underlining the need to consider interspecific interactions in wildlife reintroductions. The findings are crucial for shaping effective strategies of wildlife conservation and maintaining ecological balance.

Factor analysis of hydrologic services in water-controlled grassland ecosystems by InVEST model and geodetector.

Water conservation is highly important for a successful desert grassland ecosystem, but there was no comprehensive view on how to assess influencing factors in managing and addressing water yield and water conservation in desert steppe. The Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, which is specifically used for the assessment of ecosystem services, was combined with geographic detectors to identify the priority areas for water conservation function and analyze the driving factors of water conservation in the Tabu River Basin, Inner Mongolia Autonomous Region, China, using different meteorological data sources. (i) The InVEST model has the advantage of modeling water yield and water conservation at spatial scales by fusion downscaling data. High water yield mainly occurs in the southern hilly mountainous areas, low water yield in the northern desert and grassland areas, and between the two in the central agro-pastoral areas; the multi-year average water conservation and water yield based on the InVEST model are 3.3 and 16mm, respectively. (ii) Water yield and water conservation roughly show a transitional phenomenon of "high in the south and low in the north." The water yield and water conservation per unit area of the Tabu River Basin are relatively large for construction land, unused land, and cropland, relatively small for grassland and forestland, and basically zero for water bodies. Forest land has the strongest water conservation capacity, followed by grassland and farmland, while the order of water yield capacity is the opposite. (iii) Precipitation shows the strongest explanatory power for water yield (q = 0.427), followed by land use types (q = 0.411). The precipitation ∩ actual evapotranspiration has the strongest explanatory power for water yield (q = 0.87). The explanatory power of water yield on water conservation is the strongest (q = 0.752), followed by precipitation (q = 0.4), and the water yield ∩ soil has the greatest explanatory power on water conservation (q = 0.91). These findings are crucial for promoting regional hydrologic services and can provide a water resources management strategy for decision-makers.

Drought intensity and post-drought precipitation determine vegetation recovery in a desert steppe in Inner Mongolia, China

Extreme drought events are expected to increase in frequency and severity, posing significant threats to ecosystems worldwide. While considerable research has been concentrated on the effects of climate extremes on the stability of grasslands, the process by which grassland productivity may recover after extreme drought events are still not well understood. Here, we conducted a four-year (2019–2022) recovery investigation after four-year's (2015–2018) extreme drought treatments of different intensities (control, press and pulse) to explore the vegetation recovery of desert-grassland ecosystems Inner Mongolia, China. Press drought involved a 66 % reduction in natural precipitation from May to August, while pulse drought reduced it by 100 % during June and July. We found that both press and pulse droughts led to a sharp decrease in aboveground net primary productivity (ANPP) after four years, primarily due to reduced growth, density, and productivity of annual and perennial plants. However, ANPP under pulse drought could recover fully after four years of stopping of drought treatment, and it could not under press drought. Additionally, community structure (i.e., species richness, plant density, and height) fully recovered within 1 year after the end of the two extreme drought treatments. Both plant density and height contributed to the ANPP recovery after press and pulse droughts. Structural equation modeling (SEM) results further revealed that the reduction in ANPP during the extreme drought was primarily due to a decrease in plant density caused by reduced soil water content. The recovery of ANPP in pulse drought was directly caused by increased soil water content in the post-extreme drought. These results suggest that drought intensity and precipitation determine ANPP recovery in a degraded desert steppe. Our findings are crucial for deepening understanding of the processes and mechanisms of ecosystem recovery after extreme drought, as well as for the successful management and protection of grassland ecosystems.

Effects of UAV flight height on biomass estimation of desert shrub communities

Accurate estimation of desert vegetation biomass is crucial for monitoring changes in carbon stocks and productivity status. Unmanned aerial vehicle (UAV) remote sensing allows large-scale biomass surveys at the individual or patch scale. However, since desert shrubs are short and sparse, the UAV-based techniques do not always accurately capture biomass-related indicators at any flight height. This study investigated the effects of flight height on above-ground biomass (AGB) estimation using UAV images of typical shrub communities (Reaumuria soongarica) captured at different heights (i.e., 30 m, 50 m, 70 m, 90 m, 110 m, 130 m, and 150 m) in desert-grassland ecosystems. Several structural indicators associated with shrub allometric growth were extracted for AGB modeling, including canopy area (horizontal properties), canopy height (vertical properties), and canopy volume. Results revealed that the values of canopy height and volume decreased with increasing flight height, which made the poor performance of AGB models based on these indicators worse. For example, the variance explained (VE) of the models based on the mean canopy height decreased from about 62% to -137%, while the root mean square error (RMSE) increased from about 39 g to 92 g. In contrast, the canopy area was less affected by flight height, maintaining stable AGB models with VE around 72% and RMSE at 33 g. Adjusting the coefficients of linear models based on canopy height and volume with flight height significantly improved their predictive performance, with VE between 54% and 77% and RMSE between 30 g and 43 g for the optimized models based on mean canopy height. Furthermore, a higher flight height (e.g., 90–110 m) could be chosen to enhance operational efficiency while ensuring the accuracy of biomass observation. Our study offers valuable insights and guidance for vegetation surveys and research in desert-grassland ecosystems.

The Combination of Plant Diversity and Soil Microbial Diversity Directly and Actively Drives the Multifunctionality of Grassland Ecosystems in the Middle Part of the Northern Slopes of the Tian Shan under Grazing Disturbance

It is well known that biodiversity and ecosystem multifunctionality (EMF) guarantee the well-being of human society. Most studies have focused on the relationship between biodiversity and ecosystem function, and less is known about the individual and combined effects of above- and below-ground biodiversity on ecosystem multifunctionality under grazing disturbance. The aim of our study was to investigate the relationship between plant and soil microbial (bacterial and fungal) diversity and ecosystem multifunctionality under grazing disturbance by using multiple methods to assess ecosystem multifunctionality. We conducted experiments in desert grasslands on the northern slopes of the Tian Shan Mountains and compared the relationship between ecosystem multifunctionality and biodiversity assessed by different methods under light grazing and heavy grazing. Our results showed that at the heavy grazing level, ecosystem multifunctionality calculated by the mean method and plant diversity, soil fungal diversity, soil bacterial diversity and soil fertility calculated by the single function method showed a significant decrease (p < 0.05), but grass productivity was significantly increased (p < 0.05). Among them, ecosystem multifunctionality, soil carbon storage function and soil fertility all showed significant positive correlations with plant diversity and soil microbial diversity (p < 0.05). We calculated that ecosystem multifunctionality also essentially showed positive correlation with plant diversity and soil microbial diversity using the multi-threshold method, and the effect curve was approximately a single-peaked curve, first increasing and then decreasing. Finally, we used plant diversity, soil fungal diversity and soil bacterial diversity under grazing disturbance as biotic factors and soil pH as an abiotic factor to construct structural equation models, and we found that grazing can have direct effects on ecosystem multifunctionality and indirect effects on ecosystem multifunctionality through above- and below-ground biodiversity. Our study emphasizes the importance of the combination of above- and below-ground biodiversity in maintaining the multifunctionality of desert grassland ecosystems on the northern slopes of the Tian Shan Mountains. A moderate reduction in grazing intensity can better conserve biodiversity and improve ecosystem multifunctionality, and it is a feasible strategy to maintain sustainable management of desert grasslands.

Responses of Tillering Stipa breviflora Traits to a Long-Term Grazing Gradient

Abstract The Stipa breviflora desert steppe is an important component of the Eurasian steppe, and its ecosystem functions are directly affected by changes in the individual functional traits of S. breviflora . Based on 14 years of data from the grazing experiment in S. breviflora desert steppe, we investigated changes in the individual tillering traits of S. breviflora in response to four levels (none, light, moderate, heavy) of long-term grazing. The results showed that: ( i ) long-term grazing resulted in a greater decrease in species richness and increased biomass contribution of S. breviflora in the communities; ( ii ) long-term grazing resulted in significant differences in aboveground/belowground plant tillering functional traits and their relationships under different grazing intensities; ( iii ) the leaf biomass of S. breviflora tillering individuals was strongly dependent on leaf number, while the change in root biomass was strongly dependent on the total root length, specific root length, root furcation number, and root crossing number. The response of S. breviflora biomass to grazing intensity and its relation to tillering individual traits revealed that long-term grazing leads to vast tillering in S. breviflora tussock and significant changes in S. breviflora tillering traits, which will have a profound influence on the function of the desert grassland ecosystem.

Disturbance to biocrusts decreased cyanobacteria, N-fixer abundance, and grass leaf N but increased fungal abundance.

Interactions between plants and soil microbes influence plant nutrient transformations, including nitrogen (N) fixation, nutrient mineralization, and resource exchanges through fungal networks. Physical disturbances to soils can disrupt soil microbes and associated processes that support plant and microbial productivity. In low resource drylands, biological soil crusts ("biocrusts") occupy surface soils and house key autotrophic and diazotrophic bacteria, non-vascular plants, or lichens. Interactions among biocrusts, plants, and fungal networks between them are hypothesized to drive carbon and nutrient dynamics; however, comparisons across ecosystems are needed to generalize how soil disturbances alter microbial communities and their contributions to N pools and transformations. To evaluate linkages among plants, fungi, and biocrusts, we disturbed all unvegetated surfaces with human foot trampling twice yearly from 2013-2019 in dry conditions in cyanobacteria-dominated biocrusts in the Chihuahuan Desert grassland and shrubland ecosystems. After 5 years, disturbance decreased the abundances of cyanobacteria (especially Microcoleus steenstrupii clade) and N-fixers (Scytonema sp., and Schizothrix sp.) by >77% and chlorophyll a by up to 55% but, conversely, increased soil fungal abundance by 50% compared with controls. Responses of root-associated fungi differed between the two dominant plant species and ecosystem types, with a maximum of 80% more aseptate hyphae in disturbed than in control plots. Although disturbance did not affect 15 N tracer transfer from biocrusts to the dominant grass, Bouteloua eriopoda, disturbance increased available soil N by 65% in the shrubland, and decreased leaf N of B. eriopoda by up to 16%, suggesting that, although rapid N transfer during peak production was not affected by disturbance, over the long-term plant nutrient content was disrupted. Altogether, the shrubland may be more resilient to detrimental changes due to disturbance than grassland, and these results demonstrated that disturbances to soil microbial communities have the potential to cause substantial changes in N pools by reducing and reordering biocrust taxa.

Changes of soil bacterial and fungal community structure along a natural aridity gradient in desert grassland ecosystems, Inner Mongolia

Environmental aridity is increasing in several regions around the globe due to climate change. However, little is known about microbial diversity and community responses to aridity along grassland-to-desert gradients. We investigated soil bacterial and fungal diversity and composition, and associated environmental factors along an aridity gradient across grassland (G), desert-grassland (DG) and desert (D) in Inner Mongolia, Northern China. The results indicate that soil microbial diversity decreased significantly from G and DG to D. Bacteria were mostly dominated by the universal phyla Proteobacteria, Actinobacteria, Bacteroidetes and Acidobacteria. Fungal communities were dominated only by Ascomycota. Most bacterial species (58.7–69.1%) were found in all habitats with significant differences among the three vegetation types, while most soil fungal species occupied small geographic areas. Soil bacterial communities adapted to environmental changes through changes in proportions of their taxa, while fungi changed their rare taxa in response to the differences in local environments. Canonical correspondence analysis (CCA) indicated that soil C:N, salinity and regional temperature were the most important factors regulating microbial community composition. Structural equation models (SEM) revealed that C:N was the most important factor directly influencing soil microbial diversity, and SPEI was the most important factor indirectly influencing soil microbial diversity in the Mongolian desert-grassland ecosystem. Our results provide evidence that soil bacterial and fungal communities respond differently to the changes in the biotic and abiotic factors, reflecting different adaptive strategies for coping with climate change in desert grassland ecosystems.

The role of the locoweed (

Astragalus variabilis Bunge is a widespread locoweed that threatens livestock production in desert grassland. No research has reported its possible ecological functions due to focus being on its negative effect on livestock production. This study aimed to assess the effects of A. variabilis on soil properties and its possible role in improving soil quality in desert grassland. Soil samples were collected in Astragalus patches and the adjacent bare patches over two successive growing seasons in Alxa desert grassland where A. variabilis was favoured to spread. Soil properties including texture, water content, dry bulk density, porosity, available nutrients, organic matter, and soil microbial biomass were determined at 15 study sites. There was no significant difference in soil texture between Astragalus-dominant and bare patches; but organic matter (OM), available N and P, and microbial biomass in surface soil (0–30 cm) were significantly higher in Astragalus patches. Furthermore, microbial biomass showed a significantly positive correlation with available nutrients and OM. Levels of water soluble salt were significantly lower in A. variabilis surface soils under drought conditions. Results suggested that A. variabilis was associated with some positive changes in soil properties, and was potentially important in improving soil chemical and microbial properties in desert grassland ecosystems. Consequently, total elimination of locoweed should not necessarily be considered the best solution to locoweed poisoning in livestock.

Distribution of physiochemically defined soil organic carbon pools and their relationship to the soil microbial community in grasslands

Sequestration of carbon (C) in soils provides an important tool for climate change mitigation and grasslands offer significant potential for this approach. In this study, we examined soil organic C (SOC) protection mechanisms in alpine meadow, typical steppe and desert grassland ecosystems located in the Gansu province of China. We also examined which microbial taxonomic groups are associated with physically protected C and unprotected C.Soil samples for the study were collected from 0∼10 and 10∼20 cm soil depths from a desert in Ping Shan Hu county, typical steppe in Huanxian county and alpine meadow in Maqu county. The soil samples were subjected to the soil physiochemical fractionation to identify physically, chemically and biochemically protected and unprotected C. The soil bacterial and fungal communities were examined by DNA metabarcoding using Illumina sequencing, and redundancy analysis was used to identify microbial taxa with close associations with physically protected C and unprotected C.The alpine meadow consisted of the largest SOC stock, mostly physically protected (87.14 %), while also consisting of a large amount of unprotected C. Typical steppe and desert SOC stocks were smaller but the C was in chemically protected stable forms (86.25 % and 60.22 % respectively). The redundancy analysis identified bacterial phyla Proteobacteria, Acidobacteria and Verrucomicrobia and the fungal phyla Zygomycota and Chytridiomycota as microbial groups that were significantly related to physical C protection and unprotected C.

Drought-induced shift from a carbon sink to a carbon source in the grasslands of Inner Mongolia, China

Precipitation has an impact on both gross ecosystem productivity (GEP) and ecosystem respiration (Reco), which ultimately influences net ecosystem productivity (NEP). A positive NEP denotes an ecosystem functioning as a carbon sink; whereas, a negative NEP denotes an ecosystem functioning as a carbon source. Therefore, drought plays an important role in the carbon balance of an ecosystem. However, little is known about the point at which the ecosystem converts from a carbon sink to a carbon source in extreme droughts. Such knowledge is crucial for predicting terrestrial carbon cycling under climate change, and consequently, was the subject of this study. We imposed two types of drought treatments on desert-grassland: (1) press-drought, in which the quantity of natural precipitation was reduced by 66% from May to August; and (2) pulse-drought, in which the quantity of natural precipitation was reduced by 100% during June and July. Reco and NEP were measured and GEP was calculated and then regression analyses were employed to determine the point at which the carbon sink shifts to a carbon source. The regression equation of NEP (μmol·m−2·s−1) on Reco (μmol·m−2·s−1) took the form: NEP = 0.504 Reco – 0.086 and, consequently, when Reco equaled 0.171 μmol·m−2·s−1, there was zero change in the carbon sink and GEP also equaled 0.171 μmol·m−2·s−1. Below this value, the ecosystem functioned as a carbon source, whereas above this value, the ecosystem functioned as a carbon sink. Structural equation models (SEM) demonstrated that coverage, standing biomass, pH, soil water content and total soil carbon were the main driving factors on desert grassland ecosystem carbon fluxes.

Ecological impact assessment method of highways in Tibetan Plateau: A Case study of Gonghe-Yushu Expressway

In recent years, the ecological environment along highways in Tibetan Plateau has been severely affected due to the rapid construction of highways. In order to solve the problems of multiple indicators and inconsistent criteria in the ecological impact assessment of highways, and to scientifically screen assessment indicators, the paper proposes a multi-round indicator screening method, which combines literature analysis, expert rating, and statistical analysis. Based on this screening method, normalized difference vegetation index, land surface temperature, elevation, and normalized difference soil index are screened out. Combined with multiple linear regression, an ecological impact assessment model is established and applied to ecological impact assessment of Gonghe-Yushu Expressway. The results show that the expressway construction is the first driving force for the deterioration of the ecological environment along the roadside, and its interference range on the desert grassland ecosystem is greater than that on the agroforestry system. The ecological environment within 150 m on both sides of the expressway should be protected.

Nitrogen and phosphorus addition differentially affect plant ecological stoichiometry in desert grassland

Plant C:N:P stoichiometric relations drive powerful constraints on ecological interactions and processes. However, information about plant stoichiometric responses to N and P availability in desert grassland is limited. We conducted two field experiments with 7 levels of N (from 0.5 g to 24 g N ∙ m−2 yr−1) and P (from 0.05 g to 3.2 g P ∙ m−2 yr−1) additions in a desert grassland of Kunlun Mountain in the northwest of China to investigate the effects of these addition rates on the N and P stoichiometry of the dominant grass species Seriphidium korovinii. Nitrogen and P additions both affected plant stoichiometry. N addition suppressed P concentrations, whereas P addition had no effect on plant N concentrations. The N:P ratios of green aboveground biomass (AGB) were positively correlated with N addition ranging from 14.73 to 29.08, whereas those for P additions decreased ranging from 14.73 to 8.29. N concentrations were positively correlated with soil available N:P ratios, whereas, P concentrations were negatively correlated with soil availably N:P. Our results suggest that chemistry and stoichiometry of S. korovinii was directly affected by soil nutrient availability. Soil N availability affects S. korovinii stoichiometry to a greater extent that does soil P availability in this ecosystem. These findings suggest that N-deposition could affect the stoichiometry of this desert grassland ecosystem, and thereby potentially alter litter decomposition, plant community composition, nutrient cycling, and food-web dynamics of these desert ecosystems.

Effect of manipulated precipitation during the growing season on soil respiration in the desert-grasslands in Inner Mongolia, China

The dynamics of soil respiration are crucial in understanding carbon cycling and its feedback to climate change. However, little information exists regarding the response of soil respiration to precipitation variation. To examine the response of soil respiration to precipitation variation through biogeochemical regulation, a manipulative field experiment was conducted along a precipitation gradient (−60%, −40%, −20%, CK = natural precipitation, +20%, +40% and +60%) in a native desert grassland ecosystem in Inner Mongolia. Plant biomass, total soil carbon and soil respiration were determined across the precipitation treatments during the growing season (from late May to early October) in 2017. Above-ground biomass tended to increase but total soil carbon varied little with an increase in precipitation. Soil respiration exhibited a unimodal curve diurnally in all precipitation treatments, peaking between 09:00 and 13:00, but showed irregular patterns seasonally. Both the daily and seasonal average soil respirations increased with an increase in precipitation (diurnal Rs ranged from 0.37 μmol m−2 s−1 to 0.75 μmol m−2 s−1; seasonal Rs ranged from 0.43 μmol m−2 s−1 to 0.66 μmol m−2 s−1). Soil respiration was correlated positively with precipitation-induced change in above-ground plant biomass, but was correlated negatively with precipitation-induced change in total soil carbon. It was concluded that carbon released from the soil increases with an increase in precipitation.

Short- and long-term warming alters soil microbial community and relates to soil traits

Climatic warming abnormally alters the structure and function of terrestrial ecosystems. It is vital to understand the response of belowground biota such as soil microbial communities to warming regimes, especially in native arid areas. The present in situ experiment was established to determine the effects of climatic warming regimes on soil microbe communities and the relationships between soil microbial groups and soil physicochemical features in a desert grassland ecosystem. Two warming regimes—long-term moderate warming (T1) and short-term acute warming (T2)—were established to simulate different climatic change scenarios. Soil from each plot was collected in 2014 at the late stage of the experiment, and phospholipid fatty acid (PLFA) profiling analysis was performed to assess the composition of the soil microbial communities. It was found that warming induced a severe water deficit stress. The T2 warming regime significantly increased the ratio of bacteria to fungi (B/F), and the ratio of Gram-positive to Gram-negative bacteria (GP/GN) in August. Belowground biomass (BGB) and soil organic carbon (SOC) were significantly correlated with all of the soil microbial groups in August. The changes in B/F and GP/GN ratios might indirectly induce changes in microbial structure. It was concluded that alterations in the structure of soil microbial communities may strongly depend on growing seasons and that soil nutrient status might have a profound impact on soil microbial communities’ responses to climatic warming.