Journal of Arid Land最新文献

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District, Inner Mongolia Autonomous Region, China. This research delves into the effects of these irrigation methods on carbon dioxide (CO₂) exchange and crop growth in this region. The experimental site was divided into drip and flood irrigation zones. The irrigation schedules of this study aligned with the local commonly used irrigation schedule. We employed a developed chamber system to measure the diurnal CO₂ exchange of maize plants during various growth stages under both drip and flood irrigation methods. From May to September in 2020 and 2021, two sets of repeated experiments were conducted. In each experiment, a total of nine measurements of CO₂ exchange were performed to obtain carbon exchange data at different growth stages of maize crop. During each CO₂ exchange measurement event, CO₂ flux data were collected every two hours over a day-long period to capture the diurnal variations in CO₂ exchange. During each CO₂ exchange measurement event, the biological parameters (aboveground biomass and crop growth rate) of maize and environmental parameters (including air humidity, air temperature, precipitation, soil water content, and photosynthetically active radiation) were measured. The results indicated a V-shaped trend in net ecosystem CO₂ exchange in daytime, reducing slowly at night, while the net assimilation rate (net primary productivity) exhibited a contrasting trend. Notably, compared with flood irrigation, drip irrigation demonstrated significantly higher average daily soil CO₂ emission and greater average daily CO₂ absorption by maize plants. Consequently, within the maize ecosystem, drip irrigation appeared more conducive to absorbing atmospheric CO₂. Furthermore, drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation. A strong linear relationship existed between leaf area index and light utilization efficiency, irrespective of the irrigation method. Notably, drip irrigation displayed superior light use efficiency compared with flood irrigation. The final yield results corroborated these findings, indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation. The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District. This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

Nitrogen (N) deposition is a significant aspect of global change and poses a threat to terrestrial biodiversity. The impact of plant-soil microbe relationships to N deposition has recently attracted considerable attention. Soil microorganisms have been proven to provide nutrients for specific plant growth, especially in nutrient-poor desert steppe ecosystems. However, the effects of N deposition on plant soil microbial community interactions in such ecosystems remain poorly understood. To investigate these effects, we conducted a 6-year N-addition field experiment in a Stipa breviflora Griseb. desert steppe in Inner Mongolia Autonomous Region, northern China. Four N treatment levels (N0, N30, N50, and N100, corresponding to 0, 30, 50, and 100 kg N/(hm²•a), respectively) were applied to simulate atmospheric N deposition. The results showed that N deposition did not significantly affect the aboveground biomass of desert steppe plants. N deposition did not significantly reduce the alfa-diversity of plant and microbial communities in desert steppe, and low and mediate N additions (30 and 50 kg N/(hm²•a)) had a promoting effect on them. The variation pattern of plant Shannon index was consistent with that of the soil bacterial Chao1 index. N deposition significantly affected the beta-diversity of plants and soil bacteria, but did not significantly affect fungal communities. In conclusion, N deposition led to co-evolution between desert steppe plants and soil bacterial communities, while fungal communities exhibited strong stability and did not undergo significant changes. These findings help clarify atmospheric N deposition effects on the ecological health and function of the desert steppe.

Abstract

One of the goals of grazing management in the desert steppe is to improve its ecosystem. However, relatively little is known about soil microbe communities in the desert steppe ecosystem under grazing management. In this study, we investigated the diversity and aboveground biomass of Caragana korshinskii Kom. shrub communities in long-term fencing and grazing areas, combined with an analysis of soil physical-chemical properties and genomics, with the aim of understanding how fence management affects plant-soil-microbial inter-relationships in the desert steppe, China. The results showed that fence management (exclosure) increased plant diversity and aboveground biomass in C. korshinskii shrub area and effectively enhanced soil organic carbon (233.94%), available nitrogen (87.77%), and available phosphorus (53.67%) contents. As well, the Shannon indices of soil bacteria and fungi were greater in the fenced plot. Plant-soil changes profoundly affected the alpha- and beta-diversity of soil bacteria. Fence management also altered the soil microbial community structure, significantly increasing the relative abundances of Acidobacteriota (5.31%–8.99%), Chloroflexi (3.99%–5.58%), and Glomeromycota (1.37%–3.28%). The soil bacterial-fungal co-occurrence networks under fence management had higher complexity and connectivity. Based on functional predictions, fence management significantly increased the relative abundance of bacteria with nitrification and nitrate reduction functions and decreased the relative abundance of bacteria with nitrate and nitrite respiration functions. The relative abundances of ecologically functional fungi with arbuscular mycorrhizal fungi, ectomycorrhizal fungi, and saprotrophs also significantly increased under fence management. In addition, the differential functional groups of bacteria and fungi were closely related to plant-soil changes. The results of this study have significant positive implications for the ecological restoration and reconstruction of dry desert steppe and similar areas.

The Aral Sea was the fourth largest lake in the world but it has shrunk dramatically as a result of irrational human activities, triggering the “Aral Sea ecological crisis”. The ecological problems of the Aral Sea have attracted widespread attention, and the alleviation of the Aral Sea ecological crisis has reached a consensus among the five Central Asian countries (Kazakhstan, Uzbekistan, Tajikistan, Kyrgyzstan, and Turkmenistan). In the past decades, many ecological management measures have been implemented for the ecological restoration of the Aral Sea. However, due to the lack of regional planning and zoning, the results are not ideal. In this study, we mapped the ecological zoning of the Aral Sea from the perspective of ecological restoration based on soil type, soil salinity, surface water, groundwater table, Normalized Difference Vegetation Index (NDVI), land cover, and aerosol optical depth (AOD) data. Soil salinization and salt dust are the most prominent ecological problems in the Aral Sea. The Aral Sea was divided into seven first-level ecological restoration subregions (North Aral Sea catchment area in the downstream of the Syr Darya River (Subregion I); artificial flood overflow areas downstream of the Aral Sea (Subregion II); physical/chemical remediation area of the salt dust source area in the eastern part of the South Aral Sea (Subregion III); physical/chemical remediation areas of severe salinization in the central part of the South Aral Sea (Subregion IV); existing water surface and potential restoration areas of the South Aral Sea (Subregion V); Aral Sea vegetation natural recovery area (Subregion VI); and vegetation planting areas with light salinity in the South Aral Sea (Subregion VII)) and 14 second-level ecological restoration subregions according to the ecological zoning principles. Implementable measures are proposed for each ecological restoration subregion. For Subregion I and Subregion II with lower elevations, artificial flooding should be carried out to restore the surface of the Aral Sea. Subregion III and Subregion IV have severe soil salinization, making it difficult for vegetation to grow. In these subregions, it is recommended to cover and pave the areas with green biomatrix coverings and environmentally sustainable bonding materials. In Subregion V located in the central and western parts of the South Aral Sea, surface water recharge should be increased to ensure that this subregion can maintain normal water levels. In Subregion VI and Subregion VII where natural conditions are suitable for vegetation growth, measures such as afforestation and buffer zones should be implemented to protect vegetation. This study could provide a reference basis for future comprehensive ecological management and restoration of the Aral Sea.

Gross primary productivity (GPP) of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought. Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks, aiding efforts to mitigate the detrimental effects of climate change. In this study, we utilized the precipitation and temperature data from the Climatic Research Unit, the standardized precipitation evapotranspiration index (SPEI), the standardized precipitation index (SPI), and the simulated vegetation GPP using the eddy covariance-light use efficiency (EC-LUE) model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982–2018. The main findings indicated that vegetation GPP decreased in 50.53% of the plateau, mainly in its northern and northeastern parts, while it increased in the remaining 49.47% area. Specifically, meadow steppe (78.92%) and deciduous forest (79.46%) witnessed a significant decrease in vegetation GPP, while alpine steppe (75.08%), cropland (76.27%), and sandy vegetation (87.88%) recovered well. Warming aridification areas accounted for 71.39% of the affected areas, while 28.53% of the areas underwent severe aridification, mainly located in the south and central regions. Notably, the warming aridification areas of desert steppe (92.68%) and sandy vegetation (90.24%) were significant. Climate warming was found to amplify the sensitivity of coniferous forest, deciduous forest, meadow steppe, and alpine steppe GPP to drought. Additionally, the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased. The cumulative effect of drought on vegetation GPP persisted for 3.00–8.00 months. The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.

Vegetation restoration through artificial plantation is an effective method to combat desertification, especially in arid and semi-arid areas. This study aimed to explore the ecological effect of the plantation of Sabina vulgaris on soil physical and chemical properties on the southeastern fringe of the Mu Us Sandy Land, China. We collected soil samples from five depth layers (0–20, 20–40, 40–60, 60–80, and 80–100 cm) in the S. vulgaris plantation plots across four plantation ages (4, 7, 10, and 16 years) in November 2019, and assessed soil physical (soil bulk density, soil porosity, and soil particle size) and chemical (soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK), cation-exchange capacity (CEC), salinity, pH, and C/N ratio) properties. The results indicated that the soil predominantly consisted of sand particles (94.27%–99.67%), with the remainder being silt and clay. As plantation age increased, silt and very fine sand contents progressively rose. After 16 years of planting, there was a marked reduction in the mean soil particle size. The initial soil fertility was low and declined from 4 to 10 years of planting before witnessing an improvement. Significant positive correlations were observed for the clay, silt, and very fine sand (mean diameter of 0.000–0.100 mm) with SOC, AK, and pH. In contrast, fine sand and medium sand (mean diameter of 0.100–0.500 mm) showed significant negative correlations with these indicators. Our findings ascertain that the plantation of S. vulgaris requires 10 years to effectively act as a windbreak and contribute to sand fixation, and needs 16 years to improve soil physical and chemical properties. Importantly, these improvements were found to be highly beneficial for vegetation restoration in arid and semi-arid areas. This research can offer valuable insights for the protection and restoration of the vegetation ecosystem in the sandy lands in China.

Studying the spatiotemporal variations in ecosystem services and their interrelationships on the Loess Plateau against the background of the gully control and land consolidation (GCLC) project has significant implications for ecological protection and quality development of the Yellow River Basin. Therefore, in this study, we took Yan’an City, Shaanxi Province of China, as the study area, selected four typical ecosystem services, including soil conservation service, water yield service, carbon storage service, and habitat quality service, and quantitatively evaluated the spatiotemporal variation characteristics and trade-offs and synergies of ecosystem services from 2010 to 2018 using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. We also analysed the relationship between the GCLC project and regional ecosystem service changes in various regions (including 1 city, 2 districts, and 10 counties) of Yan’an City and proposed a coordinated development strategy between the GCLC project and the ecological environment. The results showed that, from 2010 to 2018, soil conservation service decreased by 7.76%, while the other three ecosystem services changed relatively little, with water yield service increasing by 0.56% and carbon storage service and habitat quality service decreasing by 0.16% and 0.14%, respectively. The ecological environment of Yan’an City developed in a balanced way between 2010 and 2018, and the four ecosystem services showed synergistic relationships, among which the synergistic relationships between soil conservation service and water yield service and between carbon storage service and habitat quality service were significant. The GCLC project had a negative impact on the ecosystem services of Yan’an City, and the impact on carbon storage service was more significant. This study provides a theoretical basis for the scientific evaluation of the ecological benefits of the GCLC project and the realization of a win-win situation between food security and ecological security.

Understanding the trajectories and driving mechanisms behind land use/land cover (LULC) changes is essential for effective watershed planning and management. This study quantified the net change, exchange, total change, and transfer rate of LULC in the Jinghe River Basin (JRB), China using LULC data from 2000 to 2020. Through trajectory analysis, knowledge maps, chord diagrams, and standard deviation ellipse method, we examined the spatiotemporal characteristics of LULC changes. We further established an index system encompassing natural factors (digital elevation model (DEM), slope, aspect, and curvature), socio-economic factors (gross domestic product (GDP) and population), and accessibility factors (distance from railways, distance from highways, distance from water, and distance from residents) to investigate the driving mechanisms of LULC changes using factor detector and interaction detector in the geographical detector (Geodetector). The key findings indicate that from 2000 to 2020, the JRB experienced significant LULC changes, particularly for farmland, forest, and grassland. During the study period, LULC change trajectories were categorized into stable, early-stage, late-stage, repeated, and continuous change types. Besides the stable change type, the late-stage change type predominated the LULC change trajectories, comprising 83.31% of the total change area. The period 2010–2020 witnessed more active LULC changes compared to the period 2000–2010. The LULC changes exhibited a discrete spatial expansion trend during 2000–2020, predominantly extending from southeast to northwest of the JRB. Influential driving factors on LULC changes included slope, GDP, and distance from highways. The interaction detection results imply either bilinear or nonlinear enhancement for any two driving factors impacting the LULC changes from 2000 to 2020. This comprehensive understanding of the spatiotemporal characteristics and driving mechanisms of LULC changes offers valuable insights for the planning and sustainable management of LULC in the JRB.

Climate warming profoundly affects hydrological changes, agricultural production, and human society. Arid and semi-arid areas of China are currently displaying a marked trend of warming and wetting. The Chinese Tianshan Mountains (CTM) have a high climate sensitivity, rendering the region particularly vulnerable to the effects of climate warming. In this study, we used monthly average temperature and monthly precipitation data from the CN05.1 gridded dataset (1961–2014) and 24 global climate models (GCMs) of the Coupled Model Intercomparison Project Phase 6 (CMIP6) to assess the applicability of the CMIP6 GCMs in the CTM at the regional scale. Based on this, we conducted a systematic review of the interannual trends, dry–wet transitions (based on the standardized precipitation index (SPI)), and spatial distribution patterns of climate change in the CTM during 1961–2014. We further projected future temperature and precipitation changes over three terms (near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100)) relative to the historical period (1961–2014) under four shared socio-economic pathway (SSP) scenarios (i.e., SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). It was found that the CTM had experienced significant warming and wetting from 1961 to 2014, and will also experience warming in the future (2021–2100). Substantial warming in 1997 was captured by both the CN05.1 derived from interpolating meteorological station data and the multi-model ensemble (MME) from the CMIP6 GCMs. The MME simulation results indicated an apparent wetting in 2008, which occurred later than the wetting observed from the CN05.1 in 1989. The GCMs generally underestimated spring temperature and overestimated both winter temperature and spring precipitation in the CTM. Warming and wetting are more rapid in the northern part of the CTM. By the end of the 21^st century, all the four SSP scenarios project warmer and wetter conditions in the CTM with multiple dry–wet transitions. However, the rise in precipitation fails to counterbalance the drought induced by escalating temperature in the future, so the nature of the drought in the CTM will not change at all. Additionally, the projected summer precipitation shows negative correlation with the radiative forcing. This study holds practical implications for the awareness of climate change and subsequent research in the CTM.

Abstract

The development of bare patches typically signifies a process of ecosystem degradation. Within the protection system of Shapotou section of the Baotou-Lanzhou railway, the extensive emergence of bare sand patches poses a threat to both stability and sustainability. However, there is limited knowledge regarding the morphology, dynamic changes, and ecological responses associated with these sand patches. Therefore, we analyzed the formation and development process of sand patches within the protection system and its effects on herbaceous vegetation growth and soil nutrients through field observation, survey, and indoor analysis methods. The results showed that sand patch development can be divided into three stages, i.e., formation, expansion, and stabilization, which correspond to the initial, actively developing, and semi-fixed sand patches, respectively. The average dimensions of all sand patch erosional areas were found to be 7.72 m in length, 3.91 m in width, and 0.32 m in depth. The actively developing sand patches were the largest, and the initial sand patches were the smallest. Throughout the stage of formation and expansion, the herbaceous community composition changed, and the plant density decreased by more than 50.95%. Moreover, the coverage and height of herbaceous plants decreased in the erosional area and slightly increased in the depositional lobe; and the fine particles and nutrients of soils in the erosional area and depositional lobe showed a decreasing trend. In the stabilization phases of sand patches, the area from the inlet to the bottom of sand patches becomes initially covered with crusts. Vegetation and 0–2 cm surface soil condition improved in the erosional area, but this improvement was not yet evident in the depositional lobe. Factors such as disturbance, climate change, and surface resistance to erosion exert notable influences on the formation and dynamics of sand patches. The results can provide evidence for the future treatment of sand patches and the management of the protection system of Shapotou section of the Baotou-Lanzhou railway.