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- Response of vegetation variation to climate change and human activities in
the Shiyang River Basin of China during 2001–2022-
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Abstract: Abstract Understanding the response of vegetation variation to climate change and human activities is critical for addressing future conflicts between humans and the environment, and maintaining ecosystem stability. Here, we aimed to identify the determining factors of vegetation variation and explore the sensitivity of vegetation to temperature (SVT) and the sensitivity of vegetation to precipitation (SVP) in the Shiyang River Basin (SYRB) of China during 2001–2022. The climate data from climatic research unit (CRU), vegetation index data from Moderate Resolution Imaging Spectroradiometer (MODIS), and land use data from Landsat images were used to analyze the spatial-temporal changes in vegetation indices, climate, and land use in the SYRB and its sub-basins (i.e., upstream, midstream, and downstream basins) during 2001–2022. Linear regression analysis and correlation analysis were used to explore the SVT and SVP, revealing the driving factors of vegetation variation. Significant increasing trends (P<0.05) were detected for the enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI) in the SYRB during 2001–2022, with most regions (84%) experiencing significant variation in vegetation, and land use change was determined as the dominant factor of vegetation variation. Non-significant decreasing trends were detected in the SVT and SVP of the SYRB during 2001–2022. There were spatial differences in vegetation variation, SVT, and SVP. Although NDVI and EVI exhibited increasing trends in the upstream, midstream, and downstream basins, the change slope in the downstream basin was lower than those in the upstream and midstream basins, the SVT in the upstream basin was higher than those in the midstream and downstream basins, and the SVP in the downstream basin was lower than those in the upstream and midstream basins. Temperature and precipitation changes controlled vegetation variation in the upstream and midstream basins while human activities (land use change) dominated vegetation variation in the downstream basin. We concluded that there is a spatial heterogeneity in the response of vegetation variation to climate change and human activities across different sub-basins of the SYRB. These findings can enhance our understanding of the relationship among vegetation variation, climate change, and human activities, and provide a reference for addressing future conflicts between humans and the environment in the arid inland river basins.
PubDate: 2024-07-26
DOI: 10.1007/s40333-024-0059-2
- Potential distribution of Haloxylon ammodendron in Central Asia under
climate change-
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Abstract: Abstract Understanding the spatial distribution of plant species and their dynamic changes in arid areas is crucial for addressing the challenges posed by climate change. Haloxylon ammodendron shelterbelts are essential for the protection of plant resources and the control of desertification in Central Asia. Thus far, the potential suitable habitats of H. ammodendron in Central Asia are still uncertain in the future under global climate change conditions. This study utilised the maximum entropy (MaxEnt) model to combine the current distribution data of H. ammodendron with its growth-related data to analyze the potential distribution pattern of H. ammodendron across Central Asia. The results show that there are suitable habitats of H. ammodendron in the Aralkum Desert, northern slopes of the Tianshan Mountains, and the upstream of the Tarim River and western edge of the Taklimakan Desert in the Tarim Basin under the current climate conditions. The period from 2021 to 2040 is projected to undergo significant changes in the suitable habitat area of H. ammodendron in Central Asia, with a projected 15.0% decrease in the unsuitable habitat area. Inland areas farther from the ocean, such as the Caspian Sea and Aralkum Desert, will continue to experience a decrease in the suitable habitats of H. ammodendron. Regions exhibiting frequent fluctuations in the habitat suitability levels are primarily found along the axis stretching from Astana to Kazakhskiy Melkosopochnik in Kazakhstan. These regions can transition into suitable habitats under varying climate conditions, requiring the implementation of appropriate human intervention measures to prevent desertification. Future climate conditions are expected to cause an eastward shift in the geometric centre of the potential suitable habitats of H. ammodendron, with the extent of this shift amplifying alongside more greenhouse gas emissions. This study can provide theoretical support for the spatial configuration of H. ammodendron shelterbelts and desertification control in Central Asia, emphasising the importance of proactive measures to adapt to climate change in the future.
PubDate: 2024-07-26
DOI: 10.1007/s40333-024-0061-8
- Effects of gravel on the water absorption characteristics and hydraulic
parameters of stony soil-
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Abstract: Abstract The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel, where gravel could affect the water movement process in the soil. This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil. The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment. Six experimental groups with gravel contents of 0%, 10%, 20%, 30%, 40%, and 50% were established to determine the saturated hydraulic conductivity (Ks), saturated water content (θs), initial water content (θi), and retention water content (θr), and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment. The Philip model was used to fit the soil absorption process and determine the soil water absorption rate. Then the length of the characteristic wetting front depth, shape coefficient, empirical parameter, inverse intake suction and soil water suction were derived from the van Genuchten model. Finally, the hydraulic parameters mentioned above were used to fit the soil water characteristic curves, unsaturated hydraulic conductivity (Kθ) and specific water capacity (C(h)). The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content. Compared with control check treatment with gravel content of 0%, soil water absorption rates in the treatments with gravel contents of 10%, 20%, 30%, 40%, and 50% decreased by 11.47%, 17.97%, 25.24%, 29.83%, and 42.45%, respectively. As the gravel content increased, inverse intake suction gradually increased, and shape coefficient, Ks, θs, and θr gradually decreased. For the same soil water content, soil water suction and Kθ gradually decreased with increasing gravel content. At the same soil water suction, C(h) decreased with increasing gravel content, and the water use efficiency worsened. Overall, the water holding capacity, hydraulic conductivity, and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content. This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0079-y
- Historical tillage promotes grass-legume mixtures establishment and
accelerates soil microbial activity and organic carbon decomposition-
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Abstract: Abstract Perennial grass-legume mixtures have been extensively used to restore degraded grasslands, increasing grassland productivity and forage quality. Tillage is crucial for seedbed preparation and sustainable weed management for the establishment of grass-legume mixtures. However, a common concern is that intensive tillage may alter soil characteristics, leading to losses in soil organic carbon (SOC). We investigated the plant community composition, SOC, soil microbial biomass carbon (MBC), soil enzyme activities, and soil properties in long-term perennial grass-legume mixtures under two different tillage intensities (once and twice) as well as in a fenced grassland (FG). The establishment of grass-legume mixtures increased plant species diversity and plant community coverage, compared with FG. Compared with once tilled grassland (OTG), twice tilled grassland (TTG) enhanced the coverage of high-quality leguminous forage species by 380.3%. Grass-legume mixtures with historical tillage decreased SOC and dissolved organic carbon (DOC) concentrations, whereas soil MBC concentrations in OTG and TTG increased by 16.0% and 16.4%, respectively, compared with FG. TTG significantly decreased the activity of N-acetyl-β-D-glucosaminidase (NAG) by 72.3%, whereas soil enzyme β-glucosidase (βG) in OTG and TTG increased by 55.9% and 27.3%, respectively, compared with FG. Correlation analysis indicated a close association of the increase in MBC and βG activities with the rapid decline in SOC. This result suggested that MBC was a key driving factor in soil carbon storage dynamics, potentially accelerating soil carbon cycling and facilitating biogeochemical cycling. The establishment of grass-legume mixtures effectively improves forage quality and boosts plant diversity, thereby facilitating the restoration of degraded grasslands. Although tillage assists in establishing legume-grass mixtures by controlling weeds, it accelerates microbial activity and organic carbon decomposition. Our findings provide a foundation for understanding the process and effectiveness of restoration management in degraded grasslands.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0021-3
- Assessment of plant diversity of endemic species of the Saharo-Arabian
region in Egypt-
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Abstract: Abstract Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region’s global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert (the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone (SS1) distributes all the 126 endemic species, Arabian regional subzone (SS2) owns 79 taxa, and Nubo-Sindian subzone (SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis (TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., I Asphodelus refractus group, II Agathophora alopecuroides var. papillosa group, III Anvillea garcinii group, IV Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, VI Scrophularia deserti group, and VII Astragalus schimperi group. It’s crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0102-3
- Glacier area change and its impact on runoff in the Manas River Basin,
Northwest China from 2000 to 2020-
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Abstract: Abstract Understanding the distribution and dynamics of glaciers is of great significance to the management and allocation of regional water resources and socio-economic development in arid regions of Northwest China. In this study, based on 36 Landsat images, we extracted the glacier boundaries in the Manas River Basin, Northwest China from 2000 to 2020 using eCognition combined with band operation, GIS (geographic information system) spatial overlay techniques, and manual visual interpretation. We further analyzed the distribution and variation characteristics of glacier area, and simulated glacial runoff using a distributed degree-day model to explore the regulation of runoff recharge. The results showed that glacier area in the Manas River Basin as a whole showed a downward trend over the past 21 a, with a decrease of 10.86% and an average change rate of −0.54%/a. With the increase in glacier scale, the number of smaller glaciers decreased exponentially, and the number and area of larger glaciers were relatively stable. Glacier area showed a normal distribution trend of increasing first and then decreasing with elevation. About 97.92% of glaciers were distributed at 3700–4800 m, and 48.11% of glaciers were observed on the northern and northeastern slopes. The retreat rate of glaciers was the fastest (68.82%) at elevations below 3800 m. There was a clear rise in elevation at the end of glaciers. Glaciers at different slope directions showed a rapid melting trend from the western slope to the southern slope then to the northern slope. Glacial runoff in the basin showed a fluctuating upward trend in the past 21 a, with an increase rate of 0.03×108 m3/a. The average annual glacial runoff was 4.80×108 m3, of which 33.31% was distributed in the ablation season (June–September). The average annual contribution rate of glacial meltwater to river runoff was 35.40%, and glacial runoff accounted for 45.37% of the total runoff during the ablation season. In addition, precipitation and glacial runoff had complementary regulation patterns for river runoff. The findings can provide a scientific basis for water resource management in the Manas River Basin and other similar arid inland river basins.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0080-5
- Plasticity of photorespiratory carbon concentration mechanism in
Sedobassia sedoides (Pall.) Freitag & G. Kadereit under elevated CO2
concentration and salinity-
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Abstract: Abstract Rising atmospheric CO2 (carbon dioxide) concentrations and salinization are manifestations of climate change that affect plant growth and productivity. Species with an intermediate C3–C4 type of photosynthesis live in a wide range of precipitation, temperature, and soil quality, but are more often found in warm and dry habitats. One of the intermediate C3–C4 photosynthetic type is C2 photosynthesis with a carbon concentration mechanism (CCM) that reassimilates CO2 released via photorespiration. However, the ecological significance under which C2 photosynthesis has advantages over C3 and C4 plants remains largely unexplored. Salt tolerance and functioning of CCM were studied in plants from two populations (P1 and P2) of Sedobassia sedoides (Pall.) Freitag & G. Kadereit Asch. species with C2 photosynthesis exposed to 4 d and 10 d salinity (200 mM NaCl) at ambient (785.7 mg/m3, aCO2) and elevated (1571.4 mg/m3, eCO2) CO2. On the fourth day of salinity, an increase in Na+ content, activity catalase, and superoxide dismutase was observed in both populations. P2 plants showed an increase in proline content and a decrease in photosynthetic enzyme content: rubisco, phosphoenolpyruvate carboxylase (PEPC), and glycine decarboxylase (GDC), which indicated a weakening of C2 and C4 characteristics under salinity. Treatment under 10 d salinity led to an increased Na+ content and activity of cyclic electron flow around photosystem I (PSI CEF), a decreased content of K+ and GDC in both populations. P1 plants showed greater salt tolerance, which was assessed by the degree of reduction in photosynthetic enzyme content, PSI CEF activity, and changes in relative growth rate (RGR). Differences between populations were evident under the combination of eCO2 and salinity. Under long-term salinity and eCO2, more salt-tolerant P1 plants had a higher dry biomass (DW), which was positively correlated with PSI CEF activity. In less salt-tolerant P2 plants, DW correlated with transpiration and dark respiration. Thus, S. sedoides showed a high degree of photosynthetic plasticity under the influence of salinity and eCO2 through strengthening (P1 plants) and weakening C4 characteristics (P2 plants).
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0018-y
- Predicting potential invasion risks of Leucaena leucocephala (Lam.) de Wit
in the arid area of Saudi Arabia-
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Abstract: Abstract The presence of invasive plant species poses a substantial ecological impact, thus comprehensive evaluation of their potential range and risk under the influence of climate change is necessary. This study uses maximum entropy (MaxEnt) modeling to forecast the likelihood of Leucaena leucocephala (Lam.) de Wit invasion in Saudi Arabia under present and future climate change scenarios. Utilizing the MaxEnt modeling, we integrated climatic and soil data to predict habitat suitability for the invasive species. We conducted a detailed analysis of the distribution patterns of the species, using climate variables and ecological factors. We focused on the important influence of temperature seasonality, temperature annual range, and precipitation seasonality. The distribution modeling used robust measures of area under the curve (AUC) and receiver-operator characteristic (ROC) curves, to map the invasion extent, which has a high level of accuracy in identifying appropriate habitats. The complex interaction that influenced the invasion of L. leucocephala was highlighted by the environmental parameters using Jackknife test. Presently, the actual geographic area where L. leucocephala was found in Saudi Arabia was considerably smaller than the theoretical maximum range, suggesting that it had the capacity to expand further. The MaxEnt model exhibited excellent prediction accuracy and produced reliable results based on the data from the ROC curve. Precipitation and temperature were the primary factors influencing the potential distribution of L. leucocephala. Currently, an estimated area of 216,342 km2 in Saudi Arabia was at a high probability of invasion by L. leucocephala. We investigated the potential for increased invasion hazards in the future due to climate change scenarios (Shared Socioeconomic Pathways (SSPs) 245 and 585). The analysis of key climatic variables, including temperature seasonality and annual range, along with soil properties such as clay composition and nitrogen content, unveiled their substantial influence on the distribution dynamic of L. leucocephala. Our findings indicated a significant expansion of high risk zones. High-risk zones for L. leucocephala invasion in the current climate conditions had notable expansions projected under future climate scenarios, particularly evident in southern Makkah, Al Bahah, Madina, and Asir areas. The results, backed by thorough spatial studies, emphasize the need to reduce the possible ecological impacts of climate change on the spread of L. leucocephala. Moreover, the study provides valuable strategic insights for the management of invasion, highlighting the intricate relationship between climate change, habitat appropriateness, and the risks associated with invasive species. Proactive techniques are suggested to avoid and manage the spread of L. leucocephala, considering its high potential for future spread. This study enhances the overall comprehension of the dynamics of invasive species by combining modeling techniques with ecological knowledge. It also provides valuable information for decision-making to implement efficient conservation and management strategies in response to changing environmental conditions.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0020-4
- Trade-offs and synergies between ecosystem services in Yutian County along
the Keriya River Basin, Northwest China-
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Abstract: Abstract The Keriya River Basin is located in an extremely arid climate zone on the southern edge of the Tarim Basin of Northwest China, exhibiting typical mountain-oasis-desert distribution characteristics. In recent decades, climate change and human activities have exerted significant impacts on the service functions of watershed ecosystems. However, the trade-offs and synergies between ecosystem services (ESs) have not been thoroughly examined. This study aims to reveal the spatiotemporal changes in ESs within the Keriya River Basin from 1995 to 2020 as well as the trade-offs and synergies between ESs. Leveraging the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and Revised Wind Erosion Equation (RWEQ) using land use/land cover (LULC), climate, vegetation, soil, and hydrological data, we quantified the spatiotemporal changes in the five principal ESs (carbon storage, water yield, food production, wind and sand prevention, and habitat quality) of the watershed from 1995 to 2020. Spearman correlation coefficients were used to analyze the trade-offs and synergies between ES pairs. The findings reveal that water yield, carbon storage, and habitat quality exhibited relatively high levels in the upstream, while food production and wind and sand prevention dominated the midstream and downstream, respectively. Furthermore, carbon storage, food production, wind and sand prevention, and habitat quality demonstrated an increase at the watershed scale while water yield exhibited a decline from 1995 to 2020. Specifically, carbon storage, wind and sand prevention, and habitat quality presented an upward trend in the upstream but downward trend in the midstream and downstream. Food production in the midstream showed a continuously increasing trend during the study period. Trade-off relationships were identified between water yield and wind and sand prevention, water yield and carbon storage, food production and water yield, and habitat quality and wind and sand prevention. Prominent temporal and spatial synergistic relationships were observed between different ESs, notably between carbon storage and habitat quality, carbon storage and food production, food production and wind and sand prevention, and food production and habitat quality. Water resources emerged as a decisive factor for the sustainable development of the basin, thus highlighting the intricate trade-offs and synergies between water yield and the other four services, particularly the relationship with food production, which warrants further attention. This research is of great significance for the protection and sustainable development of river basins in arid areas.
PubDate: 2024-07-01
DOI: 10.1007/s40333-024-0103-2
- Climate and topography regulate the spatial pattern of soil salinization
and its effects on shrub community structure in Northwest China-
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Abstract: Abstract Soil salinization may affect biodiversity and species composition, leading to changes in the plant community structure. However, few studies have explored the spatial pattern of soil salinization and its effects on shrub community structure at the ecosystem scale. Therefore, we conducted a transect sampling of desert shrublands in Northwest China during the growing season (June–September) in 2021. Soil salinization (both the degree and type), shrub community structure (e.g., shrub density and height), and biodiversity parameters (e.g., Simpson diversity, Margalf abundance, Shannon-Wiener diversity, and Pielou evenness indices) were used to assess the effects of soil salinization on shrub community structure. The results showed that the primary degree of soil salinization in the study area was light salinization, with the area proportion of 69.8%. Whereas the main type of soil salinization was characterized as sulfate saline soil, also accounting for 69.8% of the total area. Notably, there was a significant reduction in the degree of soil salinization and a shift in the type of soil salinization from chloride saline soil to sulfate saline soil, with an increase in longitude. Regional mean annual precipitation (MAP), mean annual evapotranspiration (MAE), elevation, and slope significantly contributed to soil salinization and its geochemical differentiation. As soil salinization intensified, shrub community structure displayed increased diversity and evenness, as indicated by the increases in the Simpson diversity, Shannon-Wiener diversity, and Pielou evenness indices. Moreover, the succulent stems and leaves of Chenopodiaceae and Tamaricaceae exhibited clear advantages under these conditions. Furthermore, regional climate and topography, such as MAP, MAE, and elevation, had greater effects on the distribution of shrub plants than soil salinization. These results provide a reference for the origin and pattern of soil salinization in drylands and their effects on the community structure of halophyte shrub species.
PubDate: 2024-06-28
DOI: 10.1007/s40333-024-0060-9
- Assessment of rehabilitation strategies for lakes affected by
anthropogenic and climatic changes: A case study of the Urmia Lake, Iran-
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Abstract: Abstract Over the last three decades, more than half of the world’s large lakes and wetlands have experienced significant shrinkage, primarily due to climate change and extensive water consumption for agriculture and other human needs. The desiccation of lakes leads to severe environmental, economic, and social repercussions. Urmia Lake, located in northwestern Iran and representing a vital natural ecosystem, has experienced a volume reduction of over 90.0%. Our research evaluated diverse water management strategies within the Urmia Lake basin and prospects of inter-basin water transfers. This study focused on strategies to safeguard the environmental water rights of the Urmia Lake by utilizing the modeling and simulating (MODSIM) model. The model simulated changes in the lake’s water volume under various scenarios. These included diverting water from incoming rivers, cutting agricultural water use by 40.0%, releasing dam water in non-agricultural seasons, treated wastewater utilization, and inter-basin transfers. Analytical hierarchy process (AHP) was utilized to analyze the simulation results. Expert opinions with AHP analysis, acted as a multi-criteria decision-making tool to evaluate the simulation and determine the optimal water supply source priority for the Urmia Lake. Our findings underscore the critical importance of reducing agricultural water consumption as the foremost step in preserving the lake. Following this, inter-basin water transfers are suggested, with a detailed consideration of the inherent challenges and limitations faced by the source watersheds. It is imperative to conduct assessments on the impacts of these transfers on the downstream users and the potential environmental risks, advocating for a diplomatic and cooperative approach with adjacent country. This study also aims to forecast the volumes of water that can be transferred under different climatic conditions—drought, normal, and wet years—to inform strategic water management planning for the Urmia Lake. According to our projection, implementing the strategic scenarios outlined could significantly augment the lake’s level and volume, potentially by 3.57×109–9.38×109 m3 over the coming 10 a and 3.57×109–10.70×109 m3 in the subsequent 15 a.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0019-x
- Temporal and spatial variation and prediction of water yield and water
conservation in the Bosten Lake Basin based on the PLUS-InVEST model-
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Abstract: Abstract To comprehensively evaluate the alterations in water ecosystem service functions within arid watersheds, this study focused on the Bosten Lake Basin, which is situated in the arid region of Northwest China. The research was based on land use/land cover (LULC), natural, socioeconomic, and accessibility data, utilizing the Patch-level Land Use Simulation (PLUS) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) models to dynamically assess LULC change and associated variations in water yield and water conservation. The analyses included the evaluation of contribution indices of various land use types and the investigation of driving factors that influence water yield and water conservation. The results showed that the change of LULC in the Bosten Lake Basin from 2000 to 2020 showed a trend of increasing in cultivated land and construction land, and decreasing in grassland, forest, and unused land. The unused land of all the three predicted scenarios of 2030 (S1, a natural development scenario; S2, an ecological protection scenario; and S3, a cultivated land protection scenario) showed a decreasing trend. The scenarios S1 and S3 showed a trend of decreasing in grassland and increasing in cultivated land; while the scenario S2 showed a trend of decreasing in cultivated land and increasing in grassland. The water yield of the Bosten Lake Basin exhibited an initial decline followed by a slight increase from 2000 to 2020. The areas with higher water yield values were primarily located in the northern section of the basin, which is characterized by higher altitude. Water conservation demonstrated a pattern of initial decrease followed by stabilization, with the northeastern region demonstrating higher water conservation values. In the projected LULC scenarios of 2030, the estimated water yield under scenarios S1 and S3 was marginally greater than that under scenario S2; while the level of water conservation across all three scenarios remained rather consistent. The results showed that Hejing County is an important water conservation function zone, and the eastern part of the Xiaoyouledusi Basin is particularly important and should be protected. The findings of this study offer a scientific foundation for advancing sustainable development in arid watersheds and facilitating efficient water resource management.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0101-4
- Spatiotemporal variations of ecosystem services and driving factors in the
Tianchi Bogda Peak Natural Reserve of Xinjiang, China-
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Abstract: Abstract Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation. The Tianchi Bogda Peak Natural Reserve (TBPNR), located in Xinjiang Uygur Autonomous Region, China, is an important ecological barrier area in the temperate arid zone. The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve. In the present study, we assessed the spatiotemporal variations of four ecosystem services (including net primary productivity (NPP), water yield, soil conservation, and habitat quality) in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. In addition, the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis, and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector. During the study period, NPP and soil conservation values in the reserve increased by 48.20% and 25.56%, respectively; conversely, water yield decreased by 16.56%, and there was no significant change in habitat quality. Spatially, both NPP and habitat quality values were higher in the northern part and lower in the southern part, whereas water yield showed an opposite trend. Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation, and exhibited a trade-off relationship with water yield. Water yield and habitat quality also had a trade-off relationship. NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index (NDVI), respectively, while water yield and soil conservation were more affected by digital elevation model (DEM). Therefore, attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management. The findings of the present study provide a reference that could facilitate the sustainable utilization of ecosystem services in the typical fragile areas of Northwest China.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0058-3
- Extreme drought with seasonal timing consistently promotes CH4 uptake
through inconsistent pathways in a temperate grassland, China-
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Abstract: Abstract Methane (CH4) is a potent greenhouse gas that has a substantial impact on global warming due to its substantial influence on the greenhouse effect. Increasing extreme precipitation events, such as drought, attributable to global warming that caused by greenhouse gases, exert a profound impact on the intricate biological processes associated with CH4 uptake. Notably, the timing of extreme drought occurrence emerges as a pivotal factor influencing CH4 uptake, even when the degree of drought remains constant. However, it is still unclear how the growing season regulates the response of CH4 uptake to extreme drought. In an effort to bridge this knowledge gap, we conducted a field manipulative experiment to evaluate the impact of extreme drought on CH4 uptake during early, middle, and late growing stages in a temperate steppe of Inner Mongolia Autonomous Region, China. The result showed that all extreme drought consistently exerted positive effects on CH4 uptake regardless of seasonal timing. However, the magnitude of this effect varied depending on the timing of season, as evidenced by a stronger effect in early growing stage than in middle and late growing stages. Besides, the pathways of CH4 uptake were different from seasonal timing. Extreme drought affected soil physical-chemical properties and aboveground biomass (AGB), consequently leading to changes in CH4 uptake. The structural equation model showed that drought both in the early and middle growing stages enhanced CH4 uptake due to reduced soil water content (SWC), leading to a decrease in NO3−-N and an increase in pmoA abundance. However, drought in late growing stage primarily enhanced CH4 uptake only by decreasing SWC. Our results suggested that seasonal timing significantly contributed to regulate the impacts of extreme drought pathways and magnitudes on CH4 uptake. The findings can provide substantial implications for understanding how extreme droughts affect CH4 uptake and improve the prediction of potential ecological consequence under future climate change.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0017-z
- Impact of climate change and human activities on the spatiotemporal
dynamics of surface water area in Gansu Province, China-
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Abstract: Abstract Understanding the dynamics of surface water area and their drivers is crucial for human survival and ecosystem stability in inland arid and semi-arid areas. This study took Gansu Province, China, a typical area with complex terrain and variable climate, as the research subject. Based on Google Earth Engine, we used Landsat data and the Open-surface Water Detection Method with Enhanced Impurity Control method to monitor the spatiotemporal dynamics of surface water area in Gansu Province from 1985 to 2022, and quantitatively analyzed the main causes of regional differences in surface water area. The findings revealed that surface water area in Gansu Province expanded by 406.88 km2 from 1985 to 2022. Seasonal surface water area exhibited significant fluctuations, while permanent surface water area showed a steady increase. Notably, terrestrial water storage exhibited a trend of first decreasing and then increasing, correlated with the dynamics of surface water area. Climate change and human activities jointly affected surface hydrological processes, with the impact of climate change being slightly higher than that of human activities. Spatially, climate change affected the ‘source’ of surface water to a greater extent, while human activities tended to affect the ‘destination’ of surface water. Challenges of surface water resources faced by inland arid and semi-arid areas like Gansu Province are multifaceted. Therefore, we summarized the surface hydrology patterns typical in inland arid and semiarid areas and tailored surface water ‘supply-demand’ balance strategies. The study not only sheds light on the dynamics of surface water area in Gansu Province, but also offers valuable insights for ecological protection and surface water resource management in inland arid and semi-arid areas facing water scarcity.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0078-z
- Characterization of alpine meadow surface crack and its correlation with
root-soil properties-
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Abstract: Abstract Quantifying surface cracks in alpine meadows is a prerequisite and a key aspect in the study of grassland crack development. Crack characterization indices are crucial for the quantitative characterization of complex cracks, serving as vital factors in assessing the degree of cracking and the development morphology. So far, research on evaluating the degree of grassland degradation through crack characterization indices is rare, especially the quantitative analysis of the development of surface cracks in alpine meadows is relatively scarce. Therefore, based on the phenomenon of surface cracking during the degradation of alpine meadows in some regions of the Qinghai-Tibet Plateau, we selected the alpine meadow in the Huangcheng Mongolian Township, Menyuan Hui Autonomous County, Qinghai Province, China as the study area, used unmanned aerial vehicle (UAV) sensing technology to acquire low-altitude images of alpine meadow surface cracks at different degrees of degradation (light, medium, and heavy degradation), and analyzed the representative metrics characterizing the degree of crack development by interpreting the crack length, length density, branch angle, and burrow (rat hole) distribution density and combining them with in situ crack width and depth measurements. Finally, the correlations between the crack characterization indices and the soil and root parameters of sample plots at different degrees of degradation in the study area were analyzed using the grey relation analysis. The results revealed that with the increase of degradation, the physical and chemical properties of soil and the mechanical properties of root-soil composite changed significantly, the vegetation coverage reduced, and the root system aggregated in the surface layer of alpine meadow. As the degree of degradation increased, the fracture morphology developed from “linear” to “dendritic”, and eventually to a complex and irregular “polygonal” pattern. The crack length, width, depth, and length density were identified as the crack characterization indices via analysis of variance. The results of grey relation analysis also revealed that the crack length, width, depth, and length density were all highly correlated with root length density, and as the degradation of alpine meadows intensified, the underground biomass increased dramatically, forming a dense layer of grass felt, which has a significant impact on the formation and expansion of cracks.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0100-5
- Comparison of isotope-based linear and Bayesian mixing models in
determining moisture recycling ratio-
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Abstract: Abstract Stable water isotopes are natural tracers quantifying the contribution of moisture recycling to local precipitation, i.e., the moisture recycling ratio, but various isotope-based models usually lead to different results, which affects the accuracy of local moisture recycling. In this study, a total of 18 stations from four typical areas in China were selected to compare the performance of isotope-based linear and Bayesian mixing models and to determine local moisture recycling ratio. Among the three vapor sources including advection, transpiration, and surface evaporation, the advection vapor usually played a dominant role, and the contribution of surface evaporation was less than that of transpiration. When the abnormal values were ignored, the arithmetic averages of differences between isotope-based linear and the Bayesian mixing models were 0.9% for transpiration, 0.2% for surface evaporation, and −1.1% for advection, respectively, and the medians were 0.5%, 0.2%, and −0.8%, respectively. The importance of transpiration was slightly less for most cases when the Bayesian mixing model was applied, and the contribution of advection was relatively larger. The Bayesian mixing model was found to perform better in determining an efficient solution since linear model sometimes resulted in negative contribution ratios. Sensitivity test with two isotope scenarios indicated that the Bayesian model had a relatively low sensitivity to the changes in isotope input, and it was important to accurately estimate the isotopes in precipitation vapor. Generally, the Bayesian mixing model should be recommended instead of a linear model. The findings are useful for understanding the performance of isotope-based linear and Bayesian mixing models under various climate backgrounds.
PubDate: 2024-06-01
DOI: 10.1007/s40333-024-0016-0
- Influence of vapor pressure deficit on vegetation growth in China
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Abstract: Abstract Vapor pressure deficit (VPD) plays a crucial role in determining plant physiological functions and exerts a substantial influence on vegetation, second only to carbon dioxide (CO2). As a robust indicator of atmospheric water demand, VPD has implications for global water resources, and its significance extends to the structure and functioning of ecosystems. However, the influence of VPD on vegetation growth under climate change remains unclear in China. This study employed empirical equations to estimate the VPD in China from 2000 to 2020 based on meteorological reanalysis data of the Climatic Research Unit (CRU) Time-Series version 4.6 (TS4.06) and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA-5). Vegetation growth status was characterized using three vegetation indices, namely gross primary productivity (GPP), leaf area index (LAI), and near-infrared reflectance of vegetation (NIRv). The spatiotemporal dynamics of VPD and vegetation indices were analyzed using the Theil-Sen median trend analysis and Mann-Kendall test. Furthermore, the influence of VPD on vegetation growth and its relative contribution were assessed using a multiple linear regression model. The results indicated an overall negative correlation between VPD and vegetation indices. Three VPD intervals for the correlations between VPD and vegetation indices were identified: a significant positive correlation at VPD below 4.820 hPa, a significant negative correlation at VPD within 4.820–9.000 hPa, and a notable weakening of negative correlation at VPD above 9.000 hPa. VPD exhibited a pronounced negative impact on vegetation growth, surpassing those of temperature, precipitation, and solar radiation in absolute magnitude. CO2 contributed most positively to vegetation growth, with VPD offsetting approximately 30.00% of the positive effect of CO2. As the rise of VPD decelerated, its relative contribution to vegetation growth diminished. Additionally, the intensification of spatial variations in temperature and precipitation accentuated the spatial heterogeneity in the impact of VPD on vegetation growth in China. This research provides a theoretical foundation for addressing climate change in China, especially regarding the challenges posed by increasing VPD.
PubDate: 2024-05-17
DOI: 10.1007/s40333-024-0077-0
- Host plant traits play a crucial role in shaping the composition of
epiphytic microbiota in the arid desert, Northwest China-
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Abstract: Abstract Phyllosphere microorganisms are a crucial component of environmental microorganisms, highly influenced by host characteristics, and play a significant role in plant health and productivity. Nonetheless, the impact of host characteristics on shaping phyllosphere microbial communities of plants with different life forms remains ambiguous. Utilizing high-throughput sequencing technology, this study analyzed the diversity and community composition of phyllosphere epiphytic microorganisms (e.g., bacteria and fungi) of various plant life forms in the hinterland of the Gurbantunggut Desert, Northwest China. Functional annotation of prokaryotic taxa (FAPROTAX) and fungi function guild (FUNGuild) were employed to assess the ecological functions of microorganisms and to investigate the role of stochastic and deterministic processes in shaping phyllosphere microbial communities. Result showed a diverse array of phyllosphere epiphytic microorganisms in the desert plants, with Proteobacteria, Cyanobacteria, and Actinobacteriota dominating bacterial community, while Ascomycota and Basidiomycota were prevalent in fungal community. Comparison across different plant life forms highlighted distinct microbial communities, indicating strong filtering effects by plant characteristics. FAPROTAX prediction identified intracellular parasites (accounting for 27.44% of bacterial community abundance), chemoheterotrophy (10.12%), and phototrophy (17.41%) as the main functions of epiphytic bacteria on leaves of different life form plants. FUNGuild prediction indicated that phyllosphere epiphytic fungi primarily served as Saprotrophs (81.77%), Pathotrophs (17.41%), and Symbiotrophs (0.82%). Co-occurrence network analysis demonstrated a predominance of positive correlations among different microbial taxa. Raup-Crick dissimilarity index analysis revealed that deterministic processes predominantly influenced phyllosphere bacterial and fungal community assembly. Variance partitioning analysis and random forest modeling suggested that plant leaf functional traits significantly impacted both bacterial and fungal community composition, with fungal community composition showing a closer association with leaf nutrients and physiology compared with bacterial community composition. The distinct responses of bacterial and fungal communities to plant traits were attributed to the differing properties of bacteria and fungi, such as bacteria having higher potential dispersal rates and broader ecological niches than fungi. Overall, the results indicate that phyllosphere bacterial and fungal communities undergo similar community assembly processes, with fungi being more influenced by plant characteristics than bacteria. These findings offer novel insights into the ecology of phyllosphere microbial communities of desert plants.
PubDate: 2024-05-01
DOI: 10.1007/s40333-024-0014-2
- Environmental dynamics of nitrogen and phosphorus release from river
sediments of arid areas-
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Abstract: Abstract Human activities lead to the accumulation of a large amount of nitrogen and phosphorus in sediments in rivers. Simultaneously, nitrogen and phosphorus can be affected by environment and re-enter the upper water body, causing secondary pollution of the river water. In this study, laboratory simulation experiments were conducted initially to investigate the release of nitrogen and phosphorus from river sediments in Urumqi City and the surrounding areas in Xinjiang Uygur Autonomous Region of China and determine the factors that influence their release. The results of this study showed significant short-term differences in nitrogen and phosphorus release characteristics from sediments at different sampling points. The proposed secondary kinetics model (i.e., pseudo-second-order kinetics model) better fitted the release process of sediment nitrogen and phosphorus. The release of nitrogen and phosphorus from sediments is a complex process driven by multiple factors, therefore, we tested the influence of three factors (pH, temperature, and disturbance intensity) on the release of nitrogen and phosphorus from sediments in this study. The most amount of nitrate nitrogen (NO3−-N) was released under neutral conditions, while the most significant release of ammonia nitrogen (NH4+-N) occurred under acidic and alkaline conditions. The release of nitrite nitrogen (NO2−-N) was less affected by pH. The dissolved total phosphorus (DTP) released significantly in the alkaline water environment, while the release of dissolved organic phosphorus (DOP) was more significant in acidic water. The release amount of soluble reactive phosphorus (SRP) increased with an increase in pH. The sediments released nitrogen and phosphorus at higher temperatures, particularly NH4+-N, NO3−-N, and SRP. The highest amount of DOP was released at 15.0°C. An increase in disturbance intensity exacerbated the release of nitrogen and phosphorus from sediments. NH4+-N, DTP, and SRP levels increased linearly with the intensity of disturbance, while NO3−-N and NO2−-N were more stable. This study provides valuable information for protecting and restoring the water environment in arid areas and has significant practical reference value.
PubDate: 2024-05-01
DOI: 10.1007/s40333-024-0099-7
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