Water Conservation Capacity Research Articles

Assessing the Water Conservation Function Based on the InVEST Model: Taking Poyang Lake Region as an Example

This paper analyzes the spatiotemporal patterns, water yield and water conservation function of different land use types in Poyang Lake Region, China, during 1990–2020 by using national land use, meteorological, soil, DEM data, etc., based on the InVEST model. The results showed that: (1) Cultivated land, forestland and water area were the main land use types in Poyang Lake Region during 1990–2020. Construction land and forestland were increasing, while grassland, unused land, cultivated land and water area were decreasing. (2) The increasing construction land was mainly derived from cultivated land. Mutual transfer existed between cultivated land and forestland, as well as between cultivated land and water area. (3) With a downward–upward–downward fluctuating trend, the average annual water yield of Poyang Lake Region was 16.17 × 109 m³, and the water conservation was 53.11 × 108 m³. The average water conservation capacity was 270.98 mm. The vegetation cover area with high water conservation value was mainly concentrated in the northwest of Jiujiang City and the northeast of Poyang County. (4) The average water conservation of different land use types during 1990–2020 was ranked as follows: water area > cultivated land > forestland > construction land > grassland > unused land. The water conservation capacity was ranked as follows: water area > grassland > forestland > cultivated land > construction land > unused land.

Difference in soil water holding capacity and the influencing factors under different land use types in the alpine region of Tibet, China

To investigate the variation of soil water holding capacity under different land use types can provide scientific basis for evaluating the change characteristics and regulation mechanism of water conservation capacity in alpine ecosystems. We collected soil samples at different depth intervals (0-10, 10-20 and 20-30 cm) under three land use types (farmland, forest, and grassland) in Tibet alpine region to measure the maximum water holding capacity, capillary water holding capacity, field capacity, and basic soil physicochemical properties. The associated environmental factors (mean annual precipitation, normalized difference vegetation index, altitude, slope gradient and surface roughness) were extracted to analyze the change characteristics and influencing factors of soil water holding capacity under different land use types. The results showed that soil water holding capacity (the maximum water holding capacity, capillary water holding capacity, and field capacity) of farmland, forest, and grassland all decreased with increasing soil depth. The mean values of the maximum water holding capacity, capillary water holding capacity, and field capacity in the 0-30 cm soil layer of grassland were 379.79, 329.57 and 194.39 g·kg-1, respectively, which were significantly higher than that of farmland (301.15, 259.67, and 154.91 g·kg-1) and forest (293.09, 251.49, and 117.01 g·kg-1). Results of the redundancy analysis showed that soil properties significantly influenced soil water holding capacity, with explanation rate of 44.6%, 42.7%, 37.6% and 35.8% for total porosity, soil organic matter, capillary porosity and soil bulk density, respectively. Results of the principal component analysis showed that mean annual precipitation, normalized difference vegetation index, altitude, slope gradient, and surface roughness were the main environmental factors affecting the spatial variation of soil water holding capacity, with a cumulative contribution of 72.4%. The grassland in the alpine region of Tibet had the highest water holding capacity and could effectively prevent soil erosion. Therefore, the implementation of returning farmland to grassland and the enclosure management of degraded grassland would be conducive to improve soil water conservation capacity in the alpine regions.

Evaluation of soil and water conservation function in the Wugong mountain meadow based on the comprehensive index method

Wugong Mountain meadow landscape is well-known both at home and abroad because of its ornamental value. Our study aimed to comprehensively evaluate the function of soil and water conservation at different altitudes of Wugong Mountain meadow soil. The hydro-physical characteristics, including the soil bulk density, porosity, water content, water holding capacity, and permeability of meadow soil at 1600 m–1900 m altitudes, were analyzed. The results showed that the mountain meadow soil's hydro-physiological characteristics and water conservation function significantly differed with altitude. However, the trend of each index did not follow the same law with altitude change. There was a decrease in bulk density of the soil from 1700 m to 1900 m, but a significant increase in porosity and water-holding capacity. Despite the higher porosity and water holding capacity found at 1600 m than at 1700 m and 1800 m, a similar bulk density was found at 1600 m as 1700 m. In addition, the bulk density in the 0–20 cm layer was lower than that in the 20–40 cm layer, while the porosity and water-holding capacity were higher. A higher sequence of soil water conservation capacity was found in soil layers 0–20 cm depth at 1900, 1600, 1800, and 1700 m; in soil layers 20–40 cm depth, it was at 1900, 1800, 1700, and 1600 m. The study found that the sequence of the comprehensive performance of soil water conservation function was at 1900, 1600, 1800, and 1700 m altitudes in the Wugong mountain meadow area. Our comprehensive study of soil water conservation capacity provides a theoretical basis for the rational use of mountain meadow resources in subtropical regions.

The Ecological and Social Effects of Cropland Expansion in the HehuangValley during theMing and Qing Dynasties

In this paper, we strive to showthat the protection of the ecological environment of the Yellow River can impact regional sustainable development and human society. Based on GIS and historical documents, we selected 1640AD in the late Ming Dynasty and 1726, 1746, and 1856AD in the early and middle Qing Dynasty as time sections to reconstruct the distributions of cropland and vegetation in the Hehuang valley. Our results showed that the cropland in the Ming Dynasty was mainly distributed in the valley of Sainei;during the early and mid-Qing Dynasty, the cropland reclamation broke the boundary of the Great Wall. Furthermore, replacing vegetation with cropland resulted in the rapid decline of water conservation capacity in the medium and high mountain areas. The decline of water conservation capacity significantly contributed to the frequent occurrence of natural disasters, such as drought, flood, water erosion, and sand pressure, which led to decreased cropland output. By the mid-Qing Dynasty, the cropland area had saturated while the population was still growing, and the grain yield could not meet the demands of the expanding population. Due to both natural and social factors, two social upheavals occurred in the late Qing Dynasty, which significantly affected the development of the regional social economy. Therefore, the destruction of the ecological environment and the reduction of water conservation capacity became an important driving force for the destruction of sustainable regional development.

Water conservation capacity under climate and land use change scenarios in Changbai Mountain, China

Abstract Regional water conservation is the key to maintain water supply. Based on the data of 2000, 2010 and 2020, this paper takes Jingyu County in the Changbai Mountain as the study area. By land use conversion matrix, geostatistical analysis, InVEST model and scenario analysis, this paper aims to find out the variation of water conservation and the its related influencing factors in Changbai Mountain region. From 2000 to 2020, forest and cultivated land decreased, while grassland and developed land increased. The water conservation increased from 2.94 × 108 m3 to 4.83 × 108 m3, with a total increase of 64.29%. Forest has the highest average water conservation, followed by grassland, cultivated land and developed land. Climatic factors were important to 91.92% of the study area, whereas 6.22% of it was influenced by land use. When forest decrease in some areas, the main control factor of 48.71% of the area shifted into land use, that could lead to a sharp decrease in water conservation. Climate determines the overall spatial pattern of water conservation; land use determines the local characteristics by controlling runoff. The increase of water conservation is beneficial to improve the reserves and development potential of mineral water.

Spatiotemporal variations of water conservation function based on EOF analysis at multi time scales under different ecosystems of Heihe River Basin

Water conservation function is a critical terrestrial ecosystem service in providing water supply and achieving water security, which has raised concerns under the pressure of climate change. However, the knowledge of variance on multi-time scale, spatiotemporal dynamic, and ecosystem variance of water conservation is insufficient. In this paper, the annual, monthly, and daily scales of water conservation and the spatiotemporal pattern of monthly water conservation were estimated based on the SWAT model from 2010 to 2020 in the Heihe River Basin (HRB). Additionally, EOF (Empirical orthogonal function) analysis was conducted to decompose the time series of water conservation function distribution into temporal coefficients and spatial patterns. The HRB was categorized into six representative ecosystems with three slope grades to illustrate the variance of water conservation function. The annual water conservation depth (WC) slightly decreased (−10.36 mm/10a) from 2010 to 2020, the monthly WC was dominated by the effects of seasonal variation, and the daily WC was highly nonlinear. The high variability and importance region is mainly located in the upstream and the central area of midstream, which deserves more attention for ecological management and priority protection. Moreover, the forest ecosystem is of the highest resilience and great ecological significance, which increased risk of reduced water conservation under the lack of precipitation. Even in a forest-dominated basin, water conservation can be impacted by other ecosystems with the strong influence of human activities. Our results provide scientific evidence for the improvement of water conservation capacity and making the adapted land use policy in Yellow River basins.

Terrestrial Water Storage Dynamics: Different Roles of Climate Variability, Vegetation Change, and Human Activities across Climate Zones in China

Understanding terrestrial water storage (TWS) dynamics and associated drivers (e.g., climate variability, vegetation change, and human activities) across climate zones is essential for designing water resources management strategies in a changing environment. This study estimated TWS anomalies (TWSAs) based on the corrected Gravity Recovery and Climate Experiment (GRACE) gravity satellite data and derived driving factors for 214 watersheds across six climate zones in China. We evaluated the long-term trends and stationarities of TWSAs from 2004 to 2014 using the Mann–Kendall trend test and Augmented Dickey-Fuller stationarity test, respectively, and identified the key driving factors for TWSAs using the partial correlation analysis. The results indicated that increased TWSAs were observed in watersheds in tropical and subtropical climate zones, while decreased TWSAs were found in alpine and warm temperate watersheds. For tropical watersheds, increases in TWS were caused by increasing water conservation capacity as a result of large-scale plantations and the implementation of natural forest protection programs. For subtropical watersheds, TWS increments were driven by increasing precipitation and forestation. The decreasing tendency in TWS in warm temperate watersheds was related to intensive human activities. In the cold temperate zone, increased precipitation and soil moisture resulting from accelerated and advanced melting of frozen soils outweigh the above-ground evapotranspiration losses, which consequently led to the upward tendency in TWS in some watersheds (e.g., Xiaoxing’anling mountains). In the alpine climate zone, significant declines in TWS were caused by declined precipitation and soil moisture and increased evapotranspiration and glacier retreats due to global warming, as well as increased agriculture activities. These findings can provide critical scientific evidence and guidance for policymakers to design adaptive strategies and plans for watershed-scale water resources and forest management in different climate zones.

Fragmentation alters the soil water conservation capacity of hillside alpine meadows on the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau—known as the roof of the world and the water tower of Asia—is facing serious degradation of its ecosystems, with alpine meadows being particularly threatened. However, little is known about how the loss of mattic epipedon (the characteristic topsoil of alpine meadows) alters the water conservation capacity of the region. Here we examined the effects of different mattic epipedon coverages on surface runoff, evapotranspiration, and soil water storage under different rainfall conditions. Our results showed that the surface runoff was significantly higher under moderate rain conditions (P > 10 mm day−1) than under light rain conditions (P < 10 mm day−1), and that declining coverage significantly increased surface runoff, especially under moderate rain conditions. The average evapotranspiration at 90 %, 60 %, and 30 % mattic epipedon coverages were 5.38 mm, 5.88 mm, and 6.38 mm under non-rainfall conditions, and 0.97 mm, 1.60 mm, and 2.24 mm under moderate rain conditions. Meanwhile, mattic epipedon coverage had a positive effect on the supplementation of soil water under moderate rainfall and on the conservation of soil water under non-rainfall conditions. Overall, alpine meadows with higher mattic epipedon coverage were more effective at maintaining surface runoff and improving soil water conservation. These findings highlight the importance of conserving and restoring alpine meadows to improve the water security in the Qinghai-Tibetan Plateau and other downstream regions.

Evaluation of the water conservation capacity of the Weihe River Basin based on the Integrated Valuation of Ecosystem Services and Tradeoffs model

AbstractThe Weihe River Basin has the worst soil erosion in the Loess Plateau. As the largest tributary of the Yellow River, the water conservation capacity in the Weihe River Basin is of great significance to the Yellow River Basin and the Loess Plateau. In this study, the volume of the water conservation in the Weihe River Basin is estimated based on the Integrated Valuation of Ecosystem Services and Tradeoffs model, and the water conservation capacity of the basin is measured after excluding the influence of rainfall and evapotranspiration. The results show that from 1987 to 2019, the water conservation in the Weihe River Basin showed an overall trend of decreasing first and then increasing. The increasing trend of water conservation is greater than that of water production. The water conservation in the Weihe River Basin decreased to the lowest in 2005 and increased to the highest in 2019. Spatially, the water conservation volume is large in the south and west and small in the north and east. The water conservation volumes increase in the middle reaches of the Weihe River, the source of the Weihe River and the Jinghe River Basin. The overall capacity of the water yield and water conservation in the Weihe River Basin shows the same increasing trend. The projects of returning farms to forests and ecological management contribute to improving the water conservation capacity in the Weihe River Basin.

A healthier water use strategy in primitive forests contributes to stronger water conservation capabilities compared with secondary forests

Water conservation is an important ecological function of forest ecosystems, plant water use strategy is a key factor in regulating forest ecosystem water balance. However, there are still insufficient studies on the water conservation capacity and water use strategies of different forest types, especially in climate-sensitive areas. In this study, we determined the stable isotope values (δD, δ18O and d-excess) of plant water, soil water and precipitation from two typical stand types (primary forest and secondary forest) on Changbai Mountain to reveal plant water use and evaluated the water conservation capacity. The results indicated that rainwater infiltrated into the soil combined with piston flow and preferential flow in the primary forest, and preferential flow was the only form of flow in the secondary forest. The main tree species in the primary forest formed a relatively stable water use niche. Among them, the water use pattern of Quercus mongolica Fisch. ex Ledeb (Qm.) was transformed between shallow and deep soil layers with strong ecological plasticity. The dominant species in secondary forest derived water from similar soil layers with intense interspecific competition. By comparing the water use patterns, the secondary forest conformed to the hypothesis of “two water worlds”, while the primary forest conformed to the hypothesis of one reservoir. The primary forest ecosystem had stronger water conservation capacity than secondary forest ecosystem due to the regulable water use strategies of plants and the stable water conservation capacity of the soil. These results will provide theoretical support and a reference for plan future forest management strategies in the climate-sensitive areas.

Ecological–Economic Assessment and Managerial Significance of Water Conservation in the Headwaters of the Yellow River

The water conservation function plays a vital role in the land–water cycle. As the “Chinese water tower”, the headwaters of the Yellow River are of great significance to the safety of the Yellow River basin and even the global ecosystem. Taking the grassland ecosystem in the Yellow River source area as the research object, the InVEST water yield model with modified parameters and the ecological value evaluation of the modified equivalent factor method were used to explore the simulated spatio-temporal changes and the value of grassland water conservation from 2001 to 2020. The results show that: (1) the average total amount of water conservation in the source area is 549 × 108 m3, which is 16% of the runoff in the Yellow River basin, with a growth rate of 7.5 mm/year 1 and a contribution rate of 30%; (2) the total ecological value of grassland water conservation in 2020 is USD 340.03 × 108. The proportion of improved grassland in ecological restoration and management is only 0.51%, while the proportion of original alpine meadow reaches 67% and its ecological function and value are irreplaceable; (3) based on the comprehensive indicators of water conservation capacity, value and importance, Qumalai, Chengduo and Maduo counties are ranked as priority areas for the ecological protection of water resources.

Evaluation of Remote Sensing Ecological Index Based on Soil and Water Conservation on the Effectiveness of Management of Abandoned Mine Landscaping Transformation.

Abandoned mines are typical areas of soil erosion. Landscape transformation of abandoned mines is an important means to balance the dual objectives of regional ecological restoration and industrial heritage protection, but the secondary development and construction process of mining relics require long-term monitoring with objective scientific indicators and effective assessment of their management effectiveness. This paper takes Tongluo Mountain Mining Park in Chongqing as an example and uses a remote sensing ecological index (RSEI) based on Landsat-8 image data to assess the spatial and temporal differences in the dynamic changes in the ecological and environmental quality of tertiary relic reserves with different degrees of development and protection in the park. Results showed that: ① The effect of vegetation cover, which can significantly improve soil and water conservation capacity. ② The RSEI is applicable to the evaluation of the effectiveness of ecological management of mines with a large amount of bare soil areas. ③ The mean value of the RSEI in the region as a whole increased by 0.090, and the mean values of the RSEI in the primary, secondary and tertiary relic reserves increased by 0.121, 0.112 and 0.006, respectively. ④ The increase in the RSEI in the study area is mainly related to the significant decrease in the dryness index (NDBSI) and the increase in the humidity index (WET). The remote sensing ecological index can objectively reflect the difference in the spatial and temporal dynamics of the ecological environment in tertiary relic protection, and this study provides a theoretical reference for the ecological assessment of secondary development-based management under difficult site conditions.

Litter storage and water-holding capacity of typical forests in mountainous area of Southwest China

Current studies on water conservation capacity of litter in the mountainous area of Southwest China (MASC) mainly focus on local scale. Such results are difficult to evaluate the storage and water-holding capacity of litter in the whole MASC. In this study, the results of site-scale research in the MASC from 2004 to 2021 were collated (a total of 16 research sites and 70 data), as well as the storage and water-holding characteristics of litters of three typical forests in the MASC were compared and analyzed. The results showed that the water-holding processes of litter in coniferous forest, broadleaved forest and mixed forest were similar, which could be divided into three stages: rapid water absorption, gradual slowing, and stable. The absorption rate and duration of different forests were different in each stage. The broadleaved forest had the fastest water absorption rate, while coniferous forest had the slowest with the longest duration to reach stability. There was no significant difference in litter storage among diffe-rent forest types. The total litter storage of coniferous forest, broadleaved forest and mixed forest ranged from 8.26 to 8.82 t·hm-2. The significant spatial variations of litter storage in semi-decomposed layer resulted in that of total litter storage. The total maximum water-holding capacity of litters of the three forests ranged from 17.85 t·hm-2 to 19.87 t·hm-2, and the maximum water-holding rate of litter ranged from 200.6% to 228.0%. There was a positive correlation between the maximum water-holding capacity and litter storage in different forests. The total effective retention capacity of three forest litters ranged from 11.66 to 12.29 t·hm-2, while the total effective retention rate of three forests ranged from 128.1% to 145.2%. There were no significant differences in litter storage and water holding capacity among three forest types with two decomposition degrees in MASC.

Assessment of Changes in Key Ecosystem Factors and Water Conservation with Remote Sensing in the Zoige

As the largest alpine peat swamp wetland distribution area in the world, the Zoige has important ecological functions, including water conservation and biodiversity maintenance. In the past 20 years, the regional ecological protection and restoration measures continuously strengthened under the leadership of the local government have led to gradual improvements in the ecological environment of the region. In this study, multisource satellite remote-sensing image data were used to carry out quantitative monitoring and assessment of the main ecological elements (vegetation and water), as well as the regional leading ecosystem service function in the Zoige. Combined with local ecological protection management policies and measures, we analyzed the characteristics and effectiveness of ecological protection. We compared the ecosystem change trends of the Zoige reserve and the county, from 2001 to 2020, and found that the fractional vegetation cover (FVC) of Zoige county has increased at a rate of 0.25%/year. The growth rate was highest between 2015 and 2020, and the growth rate of FVC in the Zoige Wetland National Nature Reserve is approximately 1.89-fold that of the whole county. The water area also shows similar variation characteristics. On the whole, the water conservation capacity of the Zoige showed a significant increase from 2001 to 2020. We used high-resolution satellite remote-sensing images to capture the details of land use changes brought about by local ecological protection policies and measures, and together with macroecological indicators, we reflected on the effectiveness of regional ecological protection measures. We observed that the ecological effects of nature reserves are more direct and rapid, and the amount of water conservation within the nature reserve is about 1 × 104 m3/km2 higher than that of the surrounding grasslands. Satellite remote-sensing images can not only capture the multiscale change information of ecological indicators, such as vegetation and water, in a timely manner, but can also help us to identify the effectiveness of conservation measures by distinguishing and analyzing the causes of these changes.

Evaluation and analysis of water conservation function of ecosystem in Shaanxi Province in China based on "Grain for Green" Projects.

The evaluation of water conservation function of the ecosystem and the analysis of influencing factors are conducive to the implementation of "Grain for Green" Projects, scientific management of land use types, and the optimization of ecosystem service functions. In this paper, we selected the data of precipitation, soil, evapotranspiration, land use/cover change, and other data to quantitatively evaluate the water conservation function of the ecosystem in Shaanxi Province from 1980 to 2015 and explored the key factors which lead to the spatial differences in water conservation functions. The results showed that (1) from 1980 to 2015, the water production and water conservation of Shaanxi Province's ecosystem based on grid units decreased by 12.81 × 108 m3 and 7.74 × 108 m3, respectively. (2) The use types of cultivated land, forest land, and grassland had a prominent contribution to the water production and water conservation of the ecosystem, while the contribution rate of water area, construction land, and unused land was small. During the research period, "Grain for Green" Projects consumed a lot of water production in a short period of time, which was not conducive to the improvement of water production capacity in Shaanxi Province. However, the conversion of cultivated land to grassland would help improve the water conservation capacity of the ecosystem, increasing the water conservation capacity by 0.77 × 108 m3. (3) The water conservation function of Shaanxi Province was "hot in the south and cold in the north," with obvious regional and spatial heterogeneity from 1980 to 2015. (4) The factors of precipitation, evapotranspiration, slope, common cultivated land area, afforestation area, and water conservation function showed a positive correlation, and the impact was significant, while the overall vegetation coverage index showed a negative correlation with it. Therefore, it is necessary to comprehensively consider the local climatic and environmental conditions to implement ecological protection and restoration policies in terms of enhancing water conservation function of the ecosystem. (5) Targeted measures are proposed for different areas in Shaanxi Province: The Northern Shaanxi area should be regarded as an ecological restoration and management area, focusing on returning farmland to grassland; Central Shaanxi Plain should be considered as an ecological protection zone, and the key task is to effectively protect the ecological land; the Southern Shaanxi area should be regarded as a key water conservation area, and the main function of the forest and grass ecosystem to conserve water is to be exerted.

Response of Runoff Yield to Land Use Changes in the Small Watershed of Core Area for 2022 Winter Olympic Games in Zhangjiakou City Based on SWAT Model

Based on an improved high-precision land use map, the SWAT model of the small watershed of the core area for the 2022 Winter Olympic Games in Zhangjiakou City was established. The model was set up, calibrated, and validated with data from 2017 to 2019. In comparison with the measured flow discharge, all the coefficient of determination values of the simulated results at the upstream, midstream, and downstream (outlet) points were larger than 0.80 in both calibration and validation periods, and the relevant Nash–Sutcliffe efficiency coefficient values were above 0.62. With the model, the response of runoff yield in the small watershed to the land use change before (2015) and after (2019) Olympic construction was simulated and analyzed. The runoff yield change was only −5.1% from 2015 to 2019, which was not statistically significant (p = 0.87 &gt; 0.05). Through simulation of two extreme scenarios, two runoff yield change coefficients were introduced to explore the effects of land use change on runoff yield. The results revealed that the neutralization effects of the land use change from grassland to forest (with strong water conservation capacity) and residential and bare land (with poor water conservation capacity) were the main reasons for the insignificant change of runoff yield. The results of this research may provide some inspiration to the application of SWAT model in small watershed and some guidance to the vegetation restoration practices for water conservation. These results can promote understanding on the response of runoff yield to the land use changes towards two extreme directions of forest land and residential and barren land, and provide some guidance for the vegetation restoration practices in the small watersheds hosting major events.

Study on sediment erosion of high head Francis turbine runner in Minjiang River basin

The Wenchuan earthquake greatly reduced the forest water conservation capacity along the banks of Minjiang River. With the intensified soil erosion and the rapid increasing sediment transport, the sediment erosion of hydraulic turbines running on the river has become more and more serious, especially of high head Francis turbines. In this study, the k-ε multiphase flow turbulence model was used to calculate the sediment-water flow of a high head Francis turbine with long and short blades in Minjiang River. The distribution pattern of sediment concentration (sediment volume fraction) on the blade surface shows that the sediment particles mainly gather on the outlet edge at 10% of the blade height on the suction surface of the long blade, while the sediment concentration on the surface of the short blade is small. The erosion of the 0Cr13Ni5Mo runner blade was tested by the flow around erosion method, and the erosion amount on the blade surface in the severe erosion area was obtained. Based on the test data of erosion and the numerical calculation results of sediment flow, a formula to calculate the sediment erosion rate of flow passage components with 0Cr13Ni5Mo material was given for turbines operating in Minjiang River. By using this formula, the sediment erosion of flow passage components in hydraulic turbines with 0Cr13Ni5Mo or similar materials operating in Minjiang River can be predicted.

Terrain gradient variations in the ecosystem services value of the Qinghai-Tibet Plateau, China

The Qinghai-Tibet Plateau is an important ecological function area in the world, but its ecosystem is very fragile owing to the alpine environment. Owing to varying landforms exhibiting significant spatial differences in terms of temperature, light, soil and water conservation capacity, topography largely determines the spatial distribution of ecosystem services in areas with complex natural conditions. Studying the impact of topography on ecosystem services is important for efficient land use and ecosystem management. However, the effects of topography on ecosystem services have rarely been studied in the Qinghai-Tibet Plateau. In this study, using land use data from 1980, 1990, 2000, 2010, and 2020, the ecosystem services value (ESV) of the Qinghai-Tibet Plateau was estimated, and its spatiotemporal variation characteristics were analyzed using the ESV equivalent factor method. Spatial autocorrelation was introduced to analyze the spatial dependency between ecosystem services and topography. The results showed that the ESV of the Qinghai-Tibet Plateau decreased from $1,700,028 million in 1980 to $1,656,0 38 million in 1990 and then steadily increased to $1,678,294 million in 2020. Moreover, the spatial distribution of the average ESV was mainly characterized by high values in the southeast region and low values in the northwest region. The ESV exhibited different geographical distributions and temporal variation characteristics across the topographic gradient, and a significant spatial dependence was observed between the average ESV and topography. Hence, priority should be given to the ecological protection of high-altitude areas, such as high mountain valley regions of the plateau.

Ecohydrological Service Characteristics of Qilian Mountain Ecosystem in the Next 30 Years Based on Scenario Simulation

Mountain ecosystems have special ecohydrological services, and the study of water conservation and soil conservation services in the Qilian Mountain Ecosystem (QLME) in China has important theoretical value for scientific understanding of the ecological processes and mechanisms of mountain ecosystems. In this study, we quantitatively estimated the spatial-temporal changes of water conservation and soil conservation services in the QLME based on the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model and estimated the future ecosystem services (ESS) of the QLME under RCP4.5 (Representative Concentration Pathways) and RCP8.5 scenarios using the coupled Geosos-FLUS model. Firstly, the QLME ecohydrological service increased from 1985 to 2018, and its spatial heterogeneity was high in the east and low in the west. Among them, water conservation first decreased and then showed a trend of fluctuating increase, and soil conservation services decreased sharply from 2010 to 2015. Secondly, there are differences in the ecohydrological services of the QLME under different land-use types. The water conservation capacity in descending order is glacier snow, grassland, forest land, wetland, and cultivated land. The soil conservation intensity from strong to weak is woodland, grassland, arable land, glacier snow, and bare land. Thirdly, under different scenarios, QLME water conservation and soil conservation functions will increase to varying degrees over the next 30 years. The water conservation in the RCP4.5 scenario is higher than that in the RCP8.5 scenario, and the higher discharge scenario will lead to the decline of the water conservation service function. The increased rate of soil conservation was greater under the RCP8.5 scenario. With the development of Nationally Determined Contributions (NDCs) and scenarios below 2 °C, the future of QLME ecohydrological services will be further understood.

Vertical variations of soil carbon under different land uses in a karst critical zone observatory (CZO), SW China

Soil is a key carbon reservoir balancing global carbon budget and regulating climate change. Barren soils in karst zones have weak capacity for soil and water conservation and are readily erodible, making the carbon biogeochemical processes within karst soils potentially rapid and complex. To explore the vertical variation of soil carbon under karst conditions and its response to land-use change, this study investigated concentrations and isotopic compositions of both soil organic and inorganic carbon (SOC and SIC) in different depths of four land-use types in a typical karst region, SW China. Results show that as soil depth increases, SOC concentrations decrease, and its δ13C ratios (from −27.3‰ to −19.4‰) increase in 0–20 cm depth but decrease at depths below 20 cm. The fresh SOC is mostly sequestered and cycled within the topsoil and subject to different controls than that of the subsoil. The turnover rate of SOC in karst soils does not directly co-vary with isotopic fractionation among different land uses. Long-term cultivation causes SOC loss from karst soils, which can be alleviated or even partially restored after farming cessation. By contrast, SIC represents < 10% of soil total carbon. The vertical heterogeneity of SIC variation and the direct influence of biological factors on SIC are both weaker relative to SOC. The low δ13C ratios of SIC (from −20.4‰ to −3.0‰) indicate there is intense dissolution and reprecipitation of pedogenic carbonate within karst soil, especially in the upper cultivated layers. These results highlight that both SOC and SIC are labile and susceptible to land-use change in karst zones, which need to be considered in estimating karst carbon sink and its role in balancing global carbon budget on variable temporal scales.