Unraveling the dynamics of the global carbon cycle and assessing the sustainability of terrestrial ecosystems are critically dependent on a comprehensive understanding of vegetation biomass. This exploration delves into the pivotal role of biomass within vegetation communities, emphasizing its impact on ecosystem health, productivity, and community structure development. These insights are invaluable for advancing ecological science and conservation efforts. The synthesis of aboveground (AGB) and belowground (BGB) biomass data from 4485 and 3442 locations across China, respectively, collates a wide range of published sources. Integrating this extensive dataset with environmental parameters and applying advanced machine learning techniques facilitated an in-depth analysis of AGB and BGB spatial patterns within China. Techniques such as variance decomposition analysis and piecewise structural equation modeling were employed to dissect the factors contributing to the spatial variability of vegetation biomass. Significant spatial heterogeneity in biomass distribution was uncovered, with vegetation biomass in the northwest markedly lower than in the southern and northeastern regions. It was observed that AGB consistently surpassed BGB. Climatic conditions, soil characteristics, and soil nutrients were found to significantly explain 53 % and 48 % of the total variance in AGB and BGB, respectively. Specifically, solar radiation and soil total nitrogen were identified as critical factors influencing variations in AGB and BGB. The findings offer profound contributions to the understanding of the global carbon balance and the evaluation of terrestrial ecosystems sustainability. Moreover, they provide essential insights into the ecosystems' response mechanisms to global changes, serving as a fundamental reference for future studies on terrestrial ecosystem carbon cycling and carbon sequestration potentials.

Using a structural equation model (SEM), this paper investigates the response of soil nitrogen content of five typical grasslands in the middle line countries of China’s “Belt and Road” initiative to the changes of climate variables, soil pH value, and normalized vegetation index, and employs the principal component analysis method to determine the spatial variation characteristics and influencing factors of nitrogen reserves in different grasslands. Pontiac grassland (PS), Middle East grassland (MES), Kazakh grassland (KS), Kazakh forest grassland (KFS), and Kazakh semi-desert grassland (KFS) are the five grasslands in the research region (KSD). The results indicated that (1) the nitrogen reserves of the five grassland soils (0–100 cm) in the research area were 7.49 Pg, or approximately 5.7 percent of the total world nitrogen reserves. The sum of the five grasslands’ 0–30 cm and 0–50 cm N reserves accounted for 36.3 percent and 63.1 percent, respectively, of the total 0–100 cm N reserves. The density of nitrogen in the soil (0–100 cm) varied significantly between grasslands, ranging from 1.47 to 3.87 kg/m², with an average of 3.10 kg/m². (2) PCA analysis revealed a substantial positive correlation between soil N and MAP (p < 0.01), a negative correlation between soil N and Srad (p < 0.01), and a high degree of similarity between the three grassland samples, KFS, KS, and KSD. (3) The decision tree algorithm determined that MAP had the most relative importance for changes in soil nitrogen content in PS, MES, and KFS, whereas Srad had the greatest relative importance for changes in soil nitrogen content in KS and KSD. The pH showed the least proportional impact for variations in soil N concentration in all five grasslands. (4) Different factors influence the change in soil N content across diverse grasslands. The principal positive driving factor of soil N content in KS and KSD is Srad, with loads of −0.39 and −0.44, respectively. The principal negative driving factor of soil N content in PS and MES is Map, with loads of 0.38 and 0.2, respectively. In the SEM model of soil nitrogen content in KFS, no environmental variables had a significant effect on N content, and the model’s R² value was 0.08, indicating an average fit.

Soil organic carbon (C) and soil total nitrogen (N) show different degrees of spatial variability at different scales. Both are important components of soil nutrients and essential elements for plant growth and development, and are closely related to biogeochemical cycles. However, there is limited information on the regional spatial validity of SOC and TN and the associated drivers at the scale of the Central Asian drylands. Therefore, this study uses the ISRIC-WISE (International Soil Reference and Information Centre-Word Inventory of Soil Property Estimates) database to conduct soil sampling at the raster level, combined with relevant climatic and environmental datasets, to investigate the spatial distribution characteristics and drivers of soil C and N in the drylands of Central Asia using classical geostatistical methods and structural equation modelling (SEM). The results of this study show that the distributions of soil C and N contents in the dry zone of Central Asia have greater similarity, with C content mainly concentrated in the ranges of 0–5.5 g/kg and 11.1–15.9 g/kg; soil N content mainly concentrated in the range of 0.4–1.1 g/kg, and the soil C:N ratio mainly concentrated in the range of 12.2–28.9. Structural equation modelling showed that the main driver of soil C change was Aridity (−0.51); the main driver of soil N change was Mean Annual Temperature (MAT) (−0.44); and soil C:N change was most influenced by Aboveground biomass (AGB) (−0.25). An analysis of the relative importance contribution showed that Aridity had the highest relative importance with regard to the change in C (32%); MAT had the highest relative importance with regard to the changes in N and C:N (29% and 40%, respectively). The above findings provide a reference for the use of soil resources in drylands and provide a scientific basis for regional differences in the response of arid ecosystems to climate change.

Potential evapotranspiration (PET) is the capacity of the sub-surface evapotranspiration process, which is determined by weather and climate conditions. As an important component of the surface energy balance and hydrological cycle, PET determines hydrothermal transport in surface ecosystems and is an important factor in regional water resource evaluation, water use efficiency, and drought prediction. Most of the existing studies have focused on the impact of PET on the ecological environment and regional climate, providing limited information on the characteristics of the regional distribution of potential evapotranspiration itself and the associated drivers. In this study, we use the Penman-Monteith (P–M) model to calculate the PET in Akmola Oblast, combined with relevant climate data, partial correlation analysis, and structural equation modelling (SEM) to investigate the spatial and temporal distribution characteristics of PET in the study area and its driving factors, as well as the influence of meteorological activity on PET after the implementation of the Green Ring Project in the capital area of Kazakhstan. The results of the study show that: (1) The PET in Akmola State presented a decreasing trend from 1991 to 2021, with a multi-year average value of 835.87 mm. There is large heterogeneity in the spatial distribution of PET, being significantly higher in the southwestern and northeastern regions of the study area than in the central region. (2) Simple and partial correlation analyses indicate that most of the correlations between meteorological and PET were significant, with strong spatial heterogeneity in the number of biased relationships between different meteorological activity and PET. The spatial characteristics of the correlations between PET and Srad (Solar radiation), VS (wind speed), and MAT (Mean annual temperature) were similar, with the strongest correlations observed in the southwestern part of Akmola State. Furthermore, the spatial distribution of the correlations between PET and SWC (soil water content) and ST (soil temperature) was similar, with stronger correlations in the central part of the study area than elsewhere. (3) The SEM demonstrated that the main drivers of PET change across the study area are Srad (0.59) and VS (0.37). In the metropolitan area, MAP (mean annual precipitation) is also a major driver of PET change, due to the implementation of the Green Ring Project, which has increased vegetation cover and improved the local environment. The results of this study highlight the impact of climate change on PET in Akmola Oblast, Kazakhstan, contributing to a better understanding of PET evolution and providing guidance for water management planning.

Biological soil crusts (biocrusts) development is a fundamental factor affecting stability by wind prevention, sand fixation, and desert surface soil stability enhancement, and aridity is an important driver for altering soil stability in drylands. The physical properties of biocrusts and binding sand quantity (BSQ) are important indicators for characterizing the stability of desert soil. The relationships between biocrust physical properties and BSQ are not clear, which is not conducive to a comprehensive understanding of the ecological functions of biocrusts. The different successional stages of biocrusts in the arid region of Northwest China were selected to study their physical properties and BSQ. The physical properties and BSQ of the different types of biocrusts were measured. The responses of the physical properties and BSQ of different types of biocrusts to aridity were analyzed. The results showed that the physical properties and BSQ increased significantly with biocrust development. The thickness, roughness, compressive strength, shear strength, and BSQ of the biocrusts show a significant increasing trend with the development and increase of biocrusts and coverage. BSQ and compressive strength increased with increasing thickness and roughness. Physical properties, physical multifunctionality (P‐SMF), and BSQ of different biocrust types showed significantly different trends with increasing aridity. The results of structural equation modeling also revealed that the P‐SMF and BSQ had different responses with increasing aridity. This study contributes to a comprehensive understanding of biocrust structure and function, particularly for wind prevention and sand fixation, as well as surface stability. This study provides a new methodology and new ideas for determining the distribution and surface stability of biocrusts and is highly important for land management and conservation in drylands.