Arid Desert Areas Research Articles

Restoration of Water Systems in Typical Open-Pit Coal Mines in the Arid Desert Area of Northwest China

Restoration of Water Systems in Typical Open-Pit Coal Mines in the Arid Desert Area of Northwest China

Temporal and spatial characteristics of vegetation coverage and their influencing factors in the Sugan Lake wetland on the northern margin of the Qinghai–Tibet Plateau

Fractional vegetation cover (FVC) is an important indicator of the development or reversal of salt marsh due to its absence in arid desert areas. Many studies have emphasized the differences in factors that affect fractional vegetation cover (FVC) in different temporal and spatial scales. However, few studies have reported on the temporal and spatial variations in vegetation coverage and their response to climate and also on the hydrological environment in inland salt marsh wetlands. Accordingly, based on a wetland community survey, different types of data, such as meteorological data, hydrological data, and Landsat remote sensing image data, recorded during the period from 1990 to 2020 were collected. The characteristics of the spatial and temporal distribution of vegetation coverage in the Sugan Lake wetland over the past 30 years were analyzed using a binary pixel model. Furthermore, a quantitative analysis on the response of vegetation coverage to hydrological and meteorological factors was undertaken. The results of the present study showed that the dimidiate pixel model had a high simulation accuracy in retrieving the vegetation coverage in inland salt marsh wetlands. The vegetation coverage of the Sugan Lake wetland increased with each year from 1990 to 2020, and its annual average was 19.34%. The spatial distribution of vegetation coverage was patchy and decreased from the center to the edge of the wetland. Within the same period, the vegetation coverage showed an increasing trend in Quan-shui and He-hong areas and a decreasing trend in the Shan-hong area. Vegetation coverage was mainly affected by various factors, such as precipitation, lake area, surface runoff, groundwater depth, and residential density, respectively. It was significantly positively correlated with precipitation (R2 = 0.56, P < 0.01), lake area (R2 = 0.50, P < 0.01), air temperature (R2 = 0.46, P < 0.01), and river system density (R2 = 0.52, P < 0.01) and negatively correlated with groundwater depth (R2 =-0.57, P < 0.01) and residential density (R2 = −0.38, P < 0.05). Implicit in these findings are complex mechanisms of change in vegetation coverage that help prevent the degradation of vegetation in fragile ecosystems.

The Effects of Oil and Gas Produced Water on Soil Bacterial Community Structure in the Arid Desert Area.

The safe utilization and risk assessment of produced water (PW) from oil and gas fields for desert irrigation have received increasing attention in recent years. In this context, this study aimed to analyze structural changes in soil bacterial community, and assess the environmental impact of PW discharge and irrigation over time. High-throughput sequencing technology was employed to examine the structure of the soil bacterial community in the constructed wetland and its surrounding desert vegetation irrigation region where PW was released for a considerable amount of time (30 years). The results revealed that long-term discharge of PW and irrigation significantly reduced the abundance of the soil bacterial community but did not significantly alter the richness and diversity of the soil bacterial community. Proteobacteria was the dominant bacterial phyla in soil, but in irrigated and drained areas, the dominant bacterial phyla changed from Alphaproteobacteria to Gammaproteobacteria, the Firmicutes abundance was significantly reduced.

Isotope variations and interrelationship characteristics of different water reservoirs during non-rainfall events in revegetation desert area, northwest China

The formation and utilization of non-rainfall water can modulate isotope variation characteristics of the atmosphere, plants and soil water reservoirs. This is especially significant for water resource management in arid desert areas where non-rainfall is an important supplemental water source. In this study, we analyzed the isotope variation and interaction characteristics of rainfall, non-rainfall, atmospheric water vapor, xylem water, leaf water and shallow soil water during non-rainfall events over two years in a revegetation desert area in northwest China. The results indicated that air temperature was the most important meteorological factor influencing isotope characteristics of rainfall, non-rainfall and atmospheric water vapor. The isotope composition was also affected by rainfall and non-rainfall amounts, which decreased with event quantity. Back trajectory analysis showed that the variation of rainfall d values were induced by different moisture sources from arid Gobi and local evapotranspiration. The non-rainfall water line is close to local meteoric water line, with both having similar origins. Non-rainfall was mainly formed by radiative cooling of evaporated water produced shortly after rain and participated in the local water recycling. The atmospheric, plant and soil water all had high d values which indicated that evaporated water was a significant water source of different water reservoirs in this area. The leaf water of Artemisia ordosica was largely replenished by non-rainfall water compared to xylem water during non-rainfall events, so foliar water uptake was an important survival mechanism for Artemisia ordosica to adapt to drought environment during non-rainfall formation. Non-rainfall water contributed to 8–16% of the xylem water and the less rainfall, the higher the contribution rate. Our results are especially meaningful for arid desert regions where global climate change increases the importance of non-rainfall water.

Constructing a new irrigation model for desert riparian forests based on response of canopy EVI loss and tree rings growth to groundwater fluctuation

Vegetation in arid desert areas plays an extremely important role in maintaining biodiversity and inhibiting desertification. Quantitative understanding of vegetation response to groundwater is essential to priming drought prevention and mitigation, which is a topic that is attracting considerable attention. However, previous studies have rarely assessed the response of vegetation to groundwater from probabilistic or stoichiometric chemical perspective. To address this question, a highly sensitive copula joint distribution of the response of enhanced vegetation index (EVI) loss to groundwater was constructed and a stoichiometric chemistry indicator of the Nitrogen (N) and Phosphorus (P) concentrations in tree rings was innovatively put forward to verify its sensitivity to groundwater. The results obtained revealed that the correlation of EVI with groundwater was better than that with SPEI and TVDI; Furthermore, the critical groundwater thresholds of the EVI loss rate, described as “beginning”, “reaching the maximum”, and “the slowest” were 3.85 m, 6.18–6.75 m, and 7.89 m, respectively. At the inter-annual scale, by measuring the N and P contents of Populus euphratica tree rings, and constructing response model of element contents to groundwater/rainfall, the key thresholds were determined at 5.20–5.31 m and 60 mm, which challenges the traditional understanding that rainfall does not bring ecological benefits to desert riparian forests. To further promote vegetation restoration, based on the response rule of EVI loss and stoichiometric chemical elements of tree rings to groundwater and the intermediate overflow rotation irrigation method, a more advanced desert riparian forest irrigation mode, named “branch-infiltration-rotation-irrigation”, is here proposed.

Soil extracellular enzyme stoichiometry reflects microbial metabolic limitations in different desert types of northwestern China

Soil extracellular enzyme activity (EEA) stoichiometry reflects the dynamic balance between microorganism metabolic demands for resources and nutrient availability. However, variations in metabolic limitations and their driving factors in arid desert areas with oligotrophic environments remain poorly understood. In this study, we investigated sites in different desert types in western China and measured the activities of two C-acquiring enzymes (β-1,4-glucosidase and β-D-cellobiohydrolase), two N-acquiring enzymes (β-1,4-N-acetylglucosaminidase and L-leucine aminopeptidase), and one organic-P-acquiring enzyme (alkaline phosphatase) to quantify and compare the metabolic limitations of soil microorganisms based on their EEA stoichiometry. The ratios of log-transformed C-, N-, and P-acquiring enzyme activities for all deserts combined were 1:1.1:0.9, which is close to the hypothetical global mean EEA stoichiometry (1:1:1). We quantified the microbial nutrient limitation by means of vector analysis using the proportional EEAs, and found that microbial metabolism was co-limited by soil C and N. For different desert types, the microbial N limitation increased in the following order: gravel desert < sand desert < mud desert < salt desert. Overall, the study area's climate explained the largest proportion of the variation in the microbial limitation (17.9 %), followed by soil abiotic factors (6.6 %) and biological factors (5.1 %). Our results confirmed that the EEA stoichiometry method can be used in microbial resource ecology research in a range of desert types, and that the soil microorganisms maintained community-level nutrient element homeostasis by adjusting enzyme production to increase uptake of scarce nutrients even in extremely oligotrophic environments such as deserts.

Study on Water Intake Characteristics and Influencing Parameters of Drinking Water Emergency Extraction Vehicle

In this paper, by analyzing the heat and mass transfer characteristics of the dehumidification runner microelement channel of a drinking water emergency extraction vehicle, a mathematical model of heat and mass transfer in the water intake process is established, and the influence of the runner parameters (adsorbent thickness, regeneration angle, rotation speed) and air parameters (treatment air temperature/humidity, regenerated air temperature/humidity) on the water intake characteristics is mainly studied. Water extraction experiments are carried out in arid desert areas and humid island environments. The test results showed that compared with the calculated data, the deviations in the temperature and humidity of the treated air outlet were 3.03% and 4.14%, respectively, and the deviation value of the water intake was 8.23% when the moisture content of the inlet air was 2 g/kg.

Response of soil water content temporal stability to stand age of Haloxylon ammodendron plantation in Alxa Desert, China.

Afforestation as an effective measure for wind and sand control has achieved remarkable results in northern China, and has also greatly changed the land use and vegetation characteristics of the region. It is important to study the spatial and temporal dynamics of soil water content (SWC) in different afforestation years and its temporal stability to understand the dynamic characteristics of SWC during afforestation. In order to reveal the spatiotemporal dynamic characteristics of SWC in desert area Haloxylon ammodendron (HA)plantations, in this study, five restorative-aged HA plantations in desert areas were selected and their SWC was measured in stratified layers for the 0-400 cm soil profile; we also analyzed the spatiotemporal dynamics and temporal stability of the SWC. The results showed that the SWC of HA plantations decreased with the increase in planting age in the measurement period, and the SWC of deep layers increased by more than that of shallow layers with planting age. Spearman's rank correlation coefficients for SWC of 0-400 cm in both 5- and 11-year-old HA plantations reached above 0.8 and were highly significantly correlated; the temporal stability of SWC tends to increase as the depth of the soil layer deepens. In contrast, the temporal stability of SWC in deeper layers (200-400 cm) of 22-, 34- and 46-year-old stands showed a decreasing trend with depth. Based on the relative difference analysis, representative sampling points can be selected to monitor the regional average SWC, but for older HA plantations, the uncertainty factor of stand age should be considered in the regional moisture simulation. This study verified that it is feasible to simulate large-scale SWC in fewer observations for HA plantations younger than 11 years old, while large errors exist for older stands, especially for deeper soils. This will help soil moisture management in HA plantations in arid desert areas.

The miR169b/NFYA1 module from the halophyte Halostachys caspica endows salt and drought tolerance in Arabidopsis through multi-pathways.

Salt and drought are the major abiotic stress factors plaguing plant growth, development and crop yields. Certain abiotic-stress tolerant plants have developed special mechanisms for adapting to adverse environments in the long process of evolution. Elucidating the molecular mechanisms by which they can exert resistance to abiotic stresses is beneficial for breeding new cultivars to guide agricultural production. Halostachys caspica, a perennial halophyte belonging to Halostachys in Amaranthaceae, is extremely tolerant to harsh environments, which is commonly grown in the saline-alkali arid desert area of Northwest, China. However, the molecular mechanism of stress tolerance is unclear. Nuclear Factor Y-A (NFYA) is a transcription factor that regulates the expression of downstream genes in plant response to adverse environments. It has also been reported that some members of the NFYA family are the main targets of miR169 in plants. In this study, we mainly focused on exploring the functions and preliminary mechanism of the miR169b/NFYA1 module from H. caspica to abiotic stress. The main results showed that RLM-RACE technology validated that HcNFYA1 was targeted by HcmiR169b, qRT-PCR revealed that HcmiR169b was repressed and HcNFYA1 was induced in the H. caspica branches under various abiotic stress as well ABA treatment and Arabidopsis stable transformation platform with molecular methods was applied to elucidate that the HcmiR169b/HcNFYA1 module conferred the salt and drought tolerance to plants by enhancing ABA synthesis and ABA signal transduction pathways, maintaining ROS homeostasis and the stability of cell membrane. HcNFYA1 is expected to be a candidate gene to improve plant resistance to salt and drought stresses.

Populus euphratica males exhibit stronger drought and salt stress resistance than females

Much attention has been paid on dioecious plants and their responses to environmental stresses. However, little information is available on sexual dimorphism in Populus euphratica Oliver, which usually grows in arid desert areas and exposes to drought and salinity stress. In this study, we investigated female and male seedlings of P. euphratica and their growth and anatomical structure, gas exchange, water and nitrogen use, oxidative stress and antioxidants under drought, salinity, and the combined stress. We found that there were no significant sexual differences in P. euphratica under control conditions (well-watered and no salt addition). However, males showed stronger resistance to drought, salinity and especially to the combined stress, as they had protective structures, higher biomass, net photosynthetic rate (Pn), water and nitrogen use, osmotic adjustment and reactive oxygen species (ROS) scavenging ability, and a lower leaf Cl– content under stress conditions. The significant sex × drought × salinity interactions for biomass, Pn, water and nitrogen use, superoxide radicals (O2–), proline and free amino acids (FAA) indicated that sexual dimorphism occurs depending on the stress gradients, implying contrasting adaptive responses and life strategies in P. euphratica females and males under stress conditions. Due to the sexual dimorphism of P. euphratica under drought and salinity stress, more severe shifts in the sex ratio of P. euphratica forests may occur under future climate change with aggravated aridity and soil salinity.

Foliar water uptake improves branch water potential and photosynthetic capacity in Calligonum mongolicum

Atmospheric water is among the most important water sources for plants in arid ecosystems and plays an important role in facilitating drought stress survival in plants. However, little is known about the specific physiological benefits of foliar water uptake (FWU) for woody plants inhabiting arid desert areas. The objective of this study was to explore the physiological responses of Calligonum mongolicum to atmospheric water uptake by the assimilating branches, with a special focus on the FWU effect on shoot water status and photosynthesis. To this end, the canopies of natural C. mongolicum plants in a desert region of northwestern China were humidified in a field in-situ misting experiment and a long-term wetting experiment, during which physiological measurements of plant water relations and photosynthetic capacity were performed, alongside the observation of FWU by H218O isotopic tracing. Following the in-situ misting experiment, the water potential of the assimilating branches was significantly higher than that of the secondary branches at midnight, suggesting that FWU resulted in a reverse water potential gradient in C. mongolicum at the branch level. The 18O isotope was markedly enriched in the assimilating branches, secondary branches, and trunk xylem following the foliar uptake of 18O labeled water, indicating that the water uptake from the atmosphere by the assimilating branches could replenish the stem. The relative water content and water potential of the assimilating branches were significantly increased by FWU. The net photosynthetic rate, stomatal conductance, and maximum photochemical efficiency of C. mongolicum plants were markedly increased following the wetting treatment. Our results clearly show that C. mongolicum is capable of FWU, and that the absorbed water could be transported downward through the xylem and improve the branch water status and photosynthetic capacity. These findings provide a new perspective for deepening our understanding of the drought survival mechanism of plants in arid environments.

Zoning and Monitoring of Meteorological Drought in Arid Desert Areas using SPI, SIAP and PN indices (Case Study: Zahedan Plain)

Zoning and Monitoring of Meteorological Drought in Arid Desert Areas using SPI, SIAP and PN indices (Case Study: Zahedan Plain)

Phytoremediation Potential and Physiological Mechanisms Underlying Metallic Extraction of Suaeda glauca, Artemisia desertorum, and Atriplex canescens

Mining activities have led to serious environmental (soil erosion, degradation of vegetation, and groundwater contamination) and human health (musculoskeletal problems, diarrheal conditions, and chronic diseases) issues at desert mining areas in northwest China. Native plant species grown naturally in desert regions show a unique tolerance to arid and semiarid conditions and are potential candidates for soil phytoremediation. Here, an ex situ experiment involving pot planting of seedlings of three native plant species (Suaeda glauca, Artemisia desertorum, and Atriplex canescens) was designed to explore their phytoremediation potential and the underlying physiological mechanism. For Zn and Cu, the three plants were all with a biological accumulation coefficient (BAC) greater than 1. For Cd, Ni, and Pb, Atriplex canescens had the highest bioaccumulation concentrations (521.52, 862.23, and 1734.59 mg/kg), with BAC values (1.06, 1.30, 1.25) greater than 1, which indicates that Atriplex canescens could be a broad-spectrum metal extraction plant. Physiological analysis (antioxidation, extracellular secretions, photosynthesis, and hydraulics) showed that the three desert plants exploited their unique strategy to protect against the stress of complex metals in soils. Moreover, the second growing period was the main heavy metal accumulation and extraction stage concomitant with highest water use efficiency (iWUE). Taken together, the three desert plants exhibited the potent heavy metal extraction ability and physiological and ecological adaptability to a harsh polluted environment in arid desert areas, providing potential resources for the bioremediation of metal-contaminated soils in an arid and semiarid desert environment.

Comparative metabolomics provides novel insights into correlation between dominant habitat factors and constituents of Stellaria Radix (Stellaria dichotoma L. var. lanceolata Bge.).

Stellaria dichotoma L. var. lanceolata Bge. (SDL) is the original plant of the traditional Chinese medicine Yinchaihu (Stellaria Radix). It is mainly distributed in the arid desert areas of northwest China, which is the genuine medicinal material and characteristic cultivated crop in Ningxia. This study aims to analyze the effects of different origins on SDL metabolites and quality, as well as to screen the dominant habitat factors affecting SDL in different origins. In this study, metabolites of SDL from nine different production areas were analyzed by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF MS) based metabolomics. And field investigations were conducted to record thirteen habitat-related indicators. Results showed that 1586 metabolites were identified in different origins, which were classified as thirteen categories including lipids, organic acids and organic heterocyclic compounds derivatives. Multivariate statistical analysis showed that the metabonomic spectra of SDL from different origins had various characteristics. What's more, co-expression network correlation analysis revealed that three metabolites modules (MEturquoise, MEbrown and MEblue) were more closely with the habitat factors and 104 hub metabolites were further screened out as the habitat-induced metabolite indicators. Besides, soil texture, soil pH value and soil total salt content were found as the dominant habitat factors which affect SDL metabolites. In conclusion, the study showed different habitat factors had various effects on SDL's quality and established relationship between them, which provide reference for revealing SDL's genuineness formation mechanism and guiding industrial crops practical production by habitat factors selection.

Hourly predictions of direct normal irradiation using an innovative hybrid LSTM model for concentrating solar power projects in hyper-arid regions

Although solar energy harnessing capacity varies considerably based on the employed solar energy technology and the meteorological conditions, accurate direct normal irradiation (DNI) prediction remains crucial for better planning and management of concentrating solar power systems. This work develops hybrid Long Short-Term Memory (LSTM) models for assessing hourly DNI using meteorological datasets that include relative humidity, air temperature, and global solar irradiation. The study proposes a unique hybrid model, combining a balance-dynamic sine–cosine (BDSCA) algorithm with an LSTM predictor. Combining optimizers and predictors, such hybrid models are rarely developed to estimate DNI, especially in smaller prediction intervals. Therefore, various commonly adopted algorithms in relevant studies have been considered references for evaluating the new hybrid algorithm. The results show that the relative errors of the proposed models do not exceed 2.07%, with a minimum correlation coefficient of 0.99. In addition, the dimensionality of inputs was reduced from four variables to the two most cost-effective variables in DNI prediction. Therefore, these suggested models are reliable for estimating DNI in the arid desert areas of Algeria and other locations with similar climatic features.

The effects of landscape change on habitat quality in arid desert areas based on future scenarios: Tarim River Basin as a case study.

Human activities have caused spatiotemporal patterns of land use and land cover (LULC) change. The LULC change has directly affected habitat quality (HQ) and ecosystem functions. Assessing, simulating, and predicting spatiotemporal changes and future trends under different scenarios of LULC-influenced HQ is beneficial to land use planners and decision-makers, helping them to formulate plans in a sustainable and responsible way. This study assesses and simulates the HQ of the Tarim River Basin (TRB) using the future land use simulation model (FLUS), the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, and partial least squares regression (PLSR). Since 2000, the TRB has experienced a declining trend in HQ from 0.449 to 0.444, especially in the lower elevations (740-2000m) and on sloped land (<10°). The decline will continue unless effective and sustainable plans are implemented to halt it. Agricultural and settlement areas have a lower HQ and a higher degree of habitat degradation than native habitats. This shows that the expansion of oasis agriculture (with an annual growth rate of 372.17 km2) and settlements (with an annual growth rate of 23.50 km2) has caused a decline in native habitat and subsequent habitat fragmentation. In other words, changes in LULC have caused a decline in the HQ. Moreover, there is a significant negative correlation between HQ and urbanization rate (p<0.01), and the PLSR also indicate that number of patches (NP), area-weighted mean fractal dimension index (FRAC_AM), percentage of landscape (PLAND), and largest patch index (LPI) were also important contributors to worsening the HQ. Therefore, the TRB urgently needs appropriate strategies to preserve its natural habitats into the future, based on the ecological priority scenario (EPS) and harmonious development scenario (HDS), which can help to maintain a high-quality habitat.

Leaf chlorophyll parameters and photosynthetic characteristic variations with stand age in a typical desert species (Haloxylon ammodendron).

As a desert shrub, Haloxylon ammodendron combines ecological, economic, and social benefits and plays an important role in the ecological conservation of arid desert areas. Understanding its physiological characteristics and its mechanism of light energy utilization is important for the conservation and utilization of H. ammodendron. Therefore, we selected five stands (5-, 11-, 22-, 34-, and 46-year-old) of H. ammodendron as research objects in the study and measured their photosynthetic light response curves by a portable open photosynthesis system (Li-6400) with a red-blue light source (6400-02B). Then, we measured the leaf chlorophyll parameters in the laboratory, calculated the photosynthetic characteristics by using Ye Zipiao’s photosynthetic model, analyzed their variation patterns across stand ages, and explored the relationships between leaf chlorophyll parameters and photosynthetic characteristics. The results showed that leaf chlorophyll parameters and photosynthetic characteristics of H. ammodendron at different stand ages were significantly different. Chl content, P nmax, and LUEmax of H. ammodendron were V-shaped with the increase of stand age. The 5-year-old H. ammodendron was in the rapid growth period, synthesized more Chl a+b content (8.47 mg g−1) only by using a narrower range of light, and the Pnmax and LUEmax were the highest with values of 36.21 μmol m−2 s−1 and 0.0344, respectively. For the 22-year-old H. ammodendron, due to environmental stress, the values of Chl a+b content, P nmax, and LUEmax were the smallest and were 2.64 mg g−1, 25.73 μmol m−2 s−1, and 0.0264, respectively. For the older H. ammodendron, its Chl content, P nmax, and LUEmax were not significantly different and tended to stabilize but were slightly higher than those of the middle-aged H. ammodendron. On the other hand, the other photosynthetic parameters did not show significant variation patterns with stand age, such as R d, AQE, LSP, LCP, and I L-sat. In addition, we found that the relationships between Chl a+b content and P nmax and between Chl a+b content and LUEmax were highly correlated, except for the older H. ammodendron. Thus, using leaf chlorophyll content as a proxy for photosynthetic capacity and light use efficiency should be considered with caution. This work will provide a scientific reference for the sustainable management of desert ecosystems and vegetation restoration in sandy areas.

Changes in Vegetation Coverage and Migration Characteristics of Center of Gravity in the Arid Desert Region of Northwest China in 30 Recent Years

Vegetation coverage is important in global landscape change patterns, but research on temporal and spatial dynamic changes and analysis of vegetation landscape pattern is relatively lacking. The present study aimed to investigate the dynamic changes of vegetation coverage in the arid desert region of Northwest China and analyze the characteristics of its center of gravity migration. The normalized difference vegetation index (NDVI) and pixel binary model were used to calculate the vegetation coverage to analyze the vegetation distribution characteristics and vegetation migration in the arid desert area in Northwest China in 1990, 1995, 2000, 2005, 2015 and 2020. The results showed that from 1990 to 2020, the proportion of light and severe vegetation coverage in the arid desert region of Northwest China increased, while the proportion of medium vegetation coverage decreased. The distribution types of medium- and high-grade vegetation generally migrate to the southeast and south, which may be mainly due to the humid climate conditions and higher population density in this direction. The vegetation center of gravity migration is mainly concentrated in the southeast-south direction. Vegetation degradation occurs in the northwest region, and vegetation improvement is the main trend in the southeast and south region. The direction of vegetation migration may be affected by precipitation and soil humidity. This study provides a theoretical basis and has certain guiding significance for desertification control, ecological sustainable management, ecological restoration, and protection in the arid desert region of Northwest China.

Scale Effects on the Relationship between Plant Diversity and Ecosystem Multifunctionality in Arid Desert Areas

Understanding the relationship between biodiversity and ecosystem multifunctionality is popular topic in ecological research. Although scale is an important factor driving changes in biodiversity and ecosystem multifunctionality, we still know little about the scale effects of the relationship between the different dimensions of biodiversity and ecosystem multifunctionality. Using plant communities in the northwest of the Qira Desert Ecosystem National Field Research Station of the Chinese Academy of Sciences in Qira County, Xinjiang, as the study object, we explored the scale effects of plant diversity and ecosystem multifunctionality at different sampling scales (5 m × 5 m, 20 m × 20 m, and 50 m × 50 m) and the relative contribution of different dimensions of diversity (species diversity, functional diversity, and phylogenetic diversity) to variation in ecosystem multifunctionality. At different scales, a significant scale effect was observed in the relationship between plant diversity and ecosystem multifunctionality. Species diversity dominated ecosystem multifunctionality at large scales (50 m × 50 m), and species diversity and ecosystem multifunctionality varied linearly between scales. Functional diversity made the greatest contribution in small scales (5 m × 5 m), and the relationship between phylogenetic diversity and ecosystem multifunctionality tended to show a single-peaked variation between scales, with a dominant effect on multifunctionality at the mesoscale (20 m × 20 m). The results of the study deepen the understanding of the scale effect of the relationship between plant diversity and ecosystem multifunctionality in arid desert areas, and help to further conserve plant diversity and maintain ecosystem multifunctionality.

Dynamic Model for Caragana korshinskii Shrub Aboveground Biomass Based on Theoretical and Allometric Growth Equations

As one of the ways to achieve carbon neutralization, shrub biomass plays an important role for natural resource management decision making in arid regions. To investigate biomass dynamic variations of Caragana korshinskii, a typical shrub found in the arid desert area of Ningxia, northwest China, we combined a nonlinear simultaneous (NLS) equation system with theoretical growth (TG) and allometric growth (AG) equations. On the basis of a large biomass survey dataset and analytical data of shrub stems, four methods (NOLS, NSUR, 2SLS, and 3SLS) of the NLS equations system were combined with the TG and AG equations. A model was subsequently established to predict the AGB growth of C. korshinskii. The absolute mean residual (AMR), root mean system error (RMSE), and adjusted determination coefficient (adj-R2) were used to evaluate the performance of the equations. Results revealed that the NSUR method of the NLS equations had better performance than other methods and the independent equations for BD and H growth and AGB. Additionally, the NSUR method exhibited extremely significant differences (p &lt; 0.0001) when compared with the equations without heteroscedasticity on the basis of the likelihood ratio (LR) test, which used the power function (PF) as the variance function. The NSUR method of the NLS equations was an efficient method for predicting the dynamic growth of AGB by combining the TG and AG equations and could estimate the carbon storage for shrubs accurately, which was important for stand productivity and carbon sequestration capacity.