Vegetation Water Consumption Research Articles

Identification of suitable vegetation restoration areas and carrying capacity thresholds on the Loess Plateau.

The Loess Plateau is one of the most ecologically fragile areas in the world. It has long faced the twin dilemmas of ecological degradation and water resource shortage. In recent decades, large-scale vegetation restoration projects have been carried out on the Loess Plateau with the aim of improving the ecological environment. However, as the vegetation cover increases, the water consumption of vegetation also increases, which further exacerbates the problem of water resource shortages. In order to effectively utilize water resources and balance the relationship between forests and water use, suitable vegetation restoration areas were identified on the Loess Plateau by constructing a vegetation suitability evaluation model based on multiple index factors (precipitation, temperature, altitude, slope, aspect, soil texture, soil depth, soil organic matter and ecological water consumption). The suitable restoration area results are given as follows: trees comprised 18.58% of the total vegetation coverage area and were mainly distributed across the central and southern Loess Plateau; shrublands comprised 32.58% of the total vegetation coverage area and were mainly distributed across the northern part of the Loess Plateau; and grasslands comprised 48.84% of the total vegetation coverage area and were mainly distributed across the western and northeastern regions of the Loess Plateau. On this basis, the Eagleson model was used to identify the bearing capacity of vegetation in the suitable restoration area. The optimal simulated vegetation coverage values of the suitable restoration areas are given as follows: grassland, 0.246-1.000; shrubland, 0.186-0.783; and trees, 0.137-0.868. These results can help guide the local ecological environment construction, offer theoretical support for the ecological restoration of similar areas and provide a scientific reference for the effective use of water resources and vegetation restoration on the Loess Plateau.

Enhanced relationship between seasonal soil moisture droughts and vegetation under climate change over China

Climate change could intensify seasonal soil moisture droughts and subsequently degrade vegetation, but it can also facilitate vegetation growth with the rising temperature and CO2 concentrations. Therefore, the change of the vegetation-drought relationship under climate change remains elusive. Here, we investigate the effects of vegetation greening (i.e., increasing leaf area index (LAI)) on seasonal soil moisture drought trends by performing a set of land surface model simulations with the Conjunctive Surface-Subsurface Process model version 2 (CSSPv2), as well as the impact of seasonal soil moisture drought change on vegetation productivity via a statistical fitting model. Our results indicate that both the impact of increasing LAI on exacerbating seasonal droughts and the impact of increasing seasonal droughts on reducing vegetation productivity have been enhanced over China during 1961–2018. Specifically, increased LAI accounts for 48 % of the rising drought frequency through escalated evapotranspiration losses, with more pronounced effects in northern semiarid regions. The decrease in vegetation stomatal conductance caused by rising CO2 concentrations limits transpiration and alleviates 11 % of the increase in drought frequency, but it cannot fully offset the drought aggravation induced by increased vegetation water consumption under climate warming. Meanwhile, increased drought frequency and intensity have reduced the upward trend in vegetation productivity by 5 % over China, and by 8 % in water-limited northern regions. Our study shows the relationship between seasonal soil moisture droughts and vegetation over China has strengthened, indicating that vegetation greening will lead to increased water shortages and further impact vegetation growth and carbon sequestration. This challenges water resources management and environmental sustainability, especially in semiarid regions.

Effects of Xerophytic Vegetation-Salix on Soil Water Redistribution in Semiarid Region

Xerophytic vegetation re-regulates and allocates water resources through canopy interception, root water uptake and transpiration, and changes the water budget among precipitation, runoff, interception and infiltration, thus having a significant impact on the processes of the hydrological cycle. In this study, we investigated the effect of xerophytic shrub-Salix on soil water redistribution and water budget through an in situ monitoring experiment combined with two-dimensional vegetation water consumption modeling. The results showed that, due to the interception effect of root water uptake, it was difficult for precipitation infiltration to recharge deep soil water and groundwater. The measured data of soil moisture content, hydraulic head and precipitation were used to verify and calibrate the performance of the soil water flow model in the vadose zone by HYDRUS-2D. The effect of roots system on soil water was simulated, and the appropriate spacing of Salix replanting was estimated. Combined with the relationship between the transverse roots system and the crown width obtained by the investigation, it was determined that the spacing between the Salix should be greater than five times the crown width, so that the balance between the water consumption of Salix and the water supply of deep soil by precipitation could be considered. The results of this study are important for estimating groundwater recharge in arid areas and provide practical vegetation replanting options for similar regions.

A dataset of monthly potential evapotranspiration at ecological stations in arid central Asia from 2005 to 2020

The potential evapotranspiration represents the atmospheric evaporation capacity, which is an important indicator to measure the regional evaporation capacity, and also a key parameter to evaluate drought degree, the balance between supply and demand of water resources, and the water consumption of vegetation. Based on the meteorological data collected by 12 ecological field stations of Central Asia Ecosystem Monitoring Network and 11 ecological field stations of China Ecosystem Research Network in the arid region of Northwest China, and by using Penman-Monteith method recommended by FAO, the potential evapotranspiration was calculated from 2005 to 2020. This dataset has a long time series and covers a variety of ecosystem types. It can be used as basic data, model input data, simulation result verification data for drought research in Central Asia, and also provide data support for the research on the rational development and utilization of water resources, ecological environmental protection and other aspects in this region.

Study on Ecological Water Demand Pressure of Forest and Grass Vegetation Construction in Northwest Loess Plateau Based on Fitting Verification

In this paper, the minimum ecological water requirement of forest and grass vegetation in different types and regions and small basins in Pingliang City was analyzed and evaluated by using the quota of water consumption for ecological construction. The actual evapotranspiration water consumption of different types of vegetation was used as the quota to calculate the appropriate ecological water demand of vegetation, and the actual evapotranspiration water consumption of vegetation was used as the quota to calculate the appropriate ecological water consumption of vegetation in this region. At the same time, in order to make the calculation result more accurate, the water consumption per unit area after the actual evapotranspiration of different regions and different types of vegetation is used as the calculation quota. In addition, according to the principles of similar vegetation types, similar site conditions and similar climate environment, the research results of He Wentao et al., Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, on the ecological water requirement of forest in the whole Jinghe River basin (He Wentao et al. Determination and calculation of ecological water requirement of forest vegetation, Journal of Soil and Water Conservation, 2004, 18(6)) were selected and compared with this study. This study verifies the reliability of the calculation results of evapotranspiration water consumption of vegetation in this area. It should be noted that He Wentao et al. also evaluated the ecological water requirement of vegetation in the whole Jinghe River basin by calculating the evapotranspiration water consumption of vegetation, and analyzed the vegetation ecological water requirement deficit in 2020 by comparing the calculated minimum ecological water requirement of vegetation in the region, so as to reflect the ecological water demand pressure faced by vegetation construction in the region. It provides a basic basis for coordinating the relationship between vegetation construction and water resources in this region.

Research on Vegetation Ecological Security in Arid Region Mountain Front River Valleys Based on Ecological Water Consumption and Water Demand

The central region of the Eurasian continent is widely affected by arid conditions, but the valleys in front of the mountains nurture ecosystems consisting of forests, shrubs, and grasslands. Preserving the ecological balance in these arid valley areas is an essential aspect of water resource planning and management. This study utilizes calculations of vegetation’s ecological water consumption and water requirements to quantitatively simulate groundwater levels. These simulated levels are then compared with the threshold depth suitable for vegetation, ultimately leading to the development of an ecological security assessment method for valley areas. The results show the following: (1) During 30 years, the water demand of river valley vegetation increased slowly, and the overall stability is about 4.82 × 108 m3. Among them, the ecological water demand of grassland is the largest. The water demand from June to August is about 68% of the whole year. (2) The results indicate that over a period of 30 years, the groundwater levels in the valley area have shown a gradual decline. The rate of decline in groundwater levels is approximately twice as fast in areas farther away from the river compared to areas closer to the river. The decline in groundwater levels typically begins in May each year. During the period of valley flooding in June, there is a temporary rise in water levels, followed by a continued decline afterwards. (3) The study area has a significant proportion of groundwater suitable areas, accounting for approximately 65% on average annually. Over the course of 30 years, the area experiencing groundwater deficiency has increased from 31% to 37%. (4) Over the past 30 years, the ratio of annual vegetation water consumption to water demand in the river valley has been slowly decreasing, and the vegetation growth status has changed from good growth to normal growth. (5) In the past 30 years, the area of ecological quality areas has decreased significantly, and most of them have been transformed into general areas. The area of ecologically fragile areas is increasing, and the area of fencing protected areas is slowly declining.

Variability analysis and the conservation capacity of soil water storage under different vegetation types in arid regions

Time-series analysis of soil water storage (SWS) can provide important information on critical hydrological variability related to soil water recharge, retention, and vegetation water consumption, all of which are highly non-linear and non-stationary, making mining and analysis extremely challenging. In this study, Multivariate Empirical Mode Decomposition (MEMD) was used to separate and analyze time-series data on soil moisture, soil temperature, and meteorological factors in three different land types (bare land [BL], grassland [GL], and shrubland [SL]) in the Mu Us Desert, Shaanxi Province, China. Path analysis was then used to reveal the driving force of periodic variability in SWS after decomposition. Using daily SWS data, two new indicators, evapotranspiration capacity (Ke) and rainfall interception capacity (Kp), were also proposed in order to improve the accuracy of soil water conservation capacity calculation. The results revealed strong time-persistent memory of SWS in all land types, with hydrological periodic variability mainly reflected on a monthly scale (34–45 d). The greatest memory period was observed in SL followed by BL and GL. Subsequent path analysis suggested that dry-wet alternation (R2=0.32–0.48) driven by interactions between precipitation, solar radiation, and saturated vapor pressure were the main causes of SWS variability in the summer. While, freeze–thaw cycles (R2=0.73–0.86) driven by the soil temperature and meteorological factors were the main causes of SWS variability in winter. In the root zone (0–150 cm), the water conservation capacity of BL, GL, and SL was 139.24, 38.24, and 24.76 mm/y, respectively. In addition, the Ke/Kp values and MEMD residual component revealed that SL has greater potential for water conservation than GL. Overall, these findings suggest that in order to conserve local groundwater aquifers, areas of BL require appropriate protection in arid regions. The results of this study provide a basis for future analyses of soil moisture variability and water conservation in arid regions.

Influence of vegetation change on water consumption in watersheds

AbstractEvapotranspiration is one of the hot issues of ecological hydrology. However, few studies have analysed the impact of vegetation changes on water consumption from the perspective of natural and artificial vegetation. Taking the Ziya River Basin as an example, the daily meteorological data from 2001 to 2015 were used to calculate the water consumption of vegetation based on the Penman–Monteith model. The results showed that the vegetation coverage increased. The total water consumption increased from 2001 (2.60 × 1,010 m3) to 2005 (2.65 × 1,010 m3) and decreased from 2005 (2.65 × 1,010 m3) to 2015 (2.40 × 1,010 m3). The water consumption per unit area in descending order was mixed forests (660 mm, annual average), croplands (640 mm), closed shrublands (581 mm), deciduous broadleaf forests (528 mm), grasslands (514 mm), savannas (459 mm), and woody savannas (454 mm). Finally, the regression equation between vegetation coverage change and water consumption was y = 0.377x + 84.516, which showed that there was a proportional relationship. Therefore, attention should be given to balancing local water allocation during vegetation restoration. The results can provide a reference for vegetation restoration policies

Spatial Water Consumption Test and Analysis of Various Typical Vegetation in the Sanjiangyuan Region

Vegetation water consumption in the Sanjiangyuan Region is of direct significance to the utilization of local water resources. To measure the actual evapotranspiration of various typical vegetation with different vegetation types in the Sanjiangyuan Region, a Lysimeter was used between November 2019 and October 2020. Additionally, the Penman–Monteith equation was used to estimate the condensation water of different vegetation types. Based on the measured data, this paper analyzes the spatial distribution of annual water consumption and annual runoff of various vegetation types. Furthermore, the spatial and temporal distribution of monthly water consumption of vegetation types on different underlying surfaces are discussed. To establish the relationship between the precipitation and runoff of various vegetation types, an artificial rainfall test was conducted. This study’s results reveal several key findings: (1) Condensation water is widespread and can be observed throughout the year. The annual condensation water volume ranges between 28.47 and 56.88 mm, which is particularly significant for the growth of alpine desert steppe and alpine steppe vegetation. (2) The annual water consumption in the Sanjiangyuan Region was higher in the south than in the north. Shrub water consumption was found to be 58.1–73.3 mm higher than that of grasses. Water consumption primarily occurred during the growing season, spanning from May to October. (3) The total water consumption in the growing season of the alpine meadow was less affected by precipitation compared to the non-growing season (from November to the next April). (4) The runoff yield can be ignored in the non-growing season when calculating water balance. However, during the growing season, the calculation of runoff cannot be ignored due to its significant impact on vegetation water consumption.

Soil water dynamics and groundwater evolutions of check dams under natural rainfall reduction in semi-arid areas

Stable regional water resource distribution is essential for ecosystems, yet soil water dynamics and groundwater evolutions of check dams remain many uncertainties under natural rainfall reduction in semi-arid areas. To explore these changeable hydrologic processes, continuous fixed-point observation and water balance models were introduced in nearly-four consecutive hydrological years (2018–2021). The results showed that soil water storage presented a downward fluctuation in each soil layer of all land uses. Moreover, the grassland profile moisture descended slowly and had deeper infiltration depths than others, which might be an ideal land-use type for the reservoir’s sustainable utilization in check dams. The results also indicated that surface soil moisture (<50 cm) could rapidly respond to a single rainfall event > 10 mm d−1, whereas deep soil moisture (>50 cm) and shallow groundwater fluctuations were mainly affected by annual cumulative precipitation. Furthermore, a conceptual hydrological model of rainwater falling to the ground, percolating through soil profiles, and reaching groundwater through different vegetation covers in check dams has been proposed. Soil infiltration rates varied under different land use types and depths, ranging from 0.82 to 3.47 cm h−1. The groundwater recharge time from accumulated annual rainfall was 69–250 days, whereas the discharge time due to vegetation water consumption and groundwater lateral movement was 66–774 days. With a decrease in annual rainfall, the recharge time gradually increased, whereas the discharge time gradually decreased. These results inaugurate new perspectives for a deeper understanding of ecohydrological equilibrium in check dams and provide theoretical insights into ecological restoration in semi-arid areas.

Quantitative assessment of vegetation suitability in China based on carbon-water balance

Driven by climate change and ecological restoration, the contradiction between rising vegetation water consumption and declining terrestrial water availability becomes more apparent in non-humid regions in China, putting significant strain on the stability of water balance pattern. Thus, evaluating scientifically the suitability of plant coverage and types from the standpoint water balance is crucial to preserve or construct a relatively stable pattern of “carbon-water balance”, while which has not been investigated thoroughly. Here the study quantified the appropriate vegetation coverage of forest, shrubland and grassland, and identified unsuitable vegetation types over China in 2018 under 2 constraints of water balance (land-atmosphere water balance and terrestrial water storage stability). The findings revealed that, majority of China was across a stable state of "carbon-water balance" in 2018, but there was still a space to lower plant coverage in about 345,052 km2 (14.87%) of China with the declines mostly falling within 0.3, in 8.94% of which vegetation types were unsustainable; vegetation adjustment is advised to be prioritized in the locations (final hotspot regions, accounting for 7.43% of vegetation area of China) with water deficit, descending terrestrial water storage and the artificial vegetation areas. This study proposed a new quantitative assessment method for vegetation suitability aiming at “carbon-water balance” and provided scientific basis and practical value for maintaining the balance between the vegetation restoration and sustainable utilization of water resources.

Effect of Smoking and Type of Nutrition on the Activity of Liver Alanine Aminotransferase and Aspartate Aminotransferase

Introduction: A healthy diet provides the body with essential nutrition that includes fluids, macronutrients, and micronutrients and calories. The liver is one of the most important organs in the body that has the function of detoxification and cleansing, and smoking causes an additional burden for the detoxification function of the liver, which can lead to inflammation and fatty liver. This study was designed to investigate the effects of smoking on liver function. Materials and Methods: This is a cross-sectional descriptive analytical study in which the relationship between smoking and the type of nutrition of liver enzymes in healthy people and people who smoke was investigated in Zabol. In this study, 150 people were selected who were divided into two groups of healthy people without smoking (75 people) and people with smoking with liver problems (75 people). Results: There was no statistical relationship between age and levels of AST and ALT liver enzymes (P&gt; 0.05), but there was a relationship between weight and levels of liver enzymes AST and ALT. Hepatitis also increased (P &lt;0.05). There was a statistical relationship between alcohol consumption with AST and ALT liver enzymes, ie the more alcohol consumption, the higher the amount of liver enzymes (P &lt;0.05). There was no statistically significant relationship between fruit and vegetable consumption, rice consumption, meat consumption and water consumption (P&gt; 0.05). Discussion and Conclusion: This relationship is positive and direct, in other words, the higher the consumption of tobacco, the higher the activity of liver enzymes ALT and AST.

Spatial and Temporal Evolution of Vegetation Water Consumption in Arid and Semi-Arid Areas against the Background of Returning Farmland to Forestland

Sustainable development in arid and semi-arid areas is largely constrained by water resources. Expanding ecological space is considered an effective way to conserve water resources. The innovation of this study is the analysis of water consumption in different land-use types from a complete watershed scale, which can evaluate space management against the background of returning farmland to forestland during the past 20 years, and provide suggestions for future space management in semi-arid areas. Based on meteorological data and GIS technology, the current study quantitatively analyzes the spatial and temporal variation characteristics of the water consumption of different vegetation growth stages in the Yanhe River Basin by using the improved Penman formula. The results show that the water consumption of vegetation in the Yanhe River Basin increased from 0.44 km³ in 2000 to 0.68 km³ in 2020. The water consumption of vegetation showed obvious spatial heterogeneity, with the highest value in the central Baota area (1.094 km³) followed by the western Ansai region (0.727 km³), whereas the consumption in the eastern Yanchang area is relatively low (0.483 km³). In addition, the annual average water consumption is (0.381 km³). The cultivated land consumes the most water (0.21 km3), while the woodland consumes the least (0.072 km³). The water consumption per unit area of forested land is the highest, reaching 190 m, and the water consumption of low-coverage grassland is the lowest, only reaching 50 m. Vegetation distribution change could be the main influencing factor of vegetation water consumption change in the Yanhe River Basin. Through the establishment of the sustainable development path of ecological space with water as the core, the high-quality development of ecological environments in arid and semi-arid areas will be achieved.

Evaluation of the temporal reconstruction methods for MODIS-based continuous daily actual evapotranspiration estimation

Monitoring continuous daily actual evapotranspiration (ET) is very useful for managing regional water resources and understanding vegetation water consumption and water use efficiency. However, the research on remote sensing-based temporal reconstruction methods for mapping continuous daily ET is still limited, lacking comparative evaluations and mechanism discussions. In the study, four reconstruction methods, including two interpolation methods (the reference evaporative fraction (ETrF) and evaporative fraction (EF) method) and two calibration methods (the advection-aridity (AA) and modified Katerji-Perrier (KP) method), were systematically evaluated to reconstruct continuous daily ET from discrete daily ET based on MODIS products and atmospheric data. Meanwhile, an additional test using in situ measurements as a perfect proxy for the retrievals on satellite overpass dates was added as a baseline case that is independent of remotely sensed ET error. The internal coupling mechanism between each model’s simulations and the underlying surface physical and atmospheric driving factors were also analyzed using the sensitivity and uncertainty analysis methods. The results demonstrated that the interpolation methods performed better and had a higher potential for improvement as the quality of remote sensing ET inputs improved. Although the underestimation errors in the remote sensing-based ET estimates propagated to subsequent reconstructions and caused underestimation to a certain extent, the four methods could still effectively simulate continuous daily ET. Among them, the EF method with a simple calculation process, which used reference quantity directly related to solar radiation, had the best performance based on in situ with an R2 of 0.8233 and an NRMSE of 0.0889. Given remote sensing estimates, the AA method was the best due to the compensation effects, with an R2 of 0.7267 and an NRMSE of 0.1442. As all methods showed high sensitivity to ET of satellite overpass days, its accuracy should be a top priority for continuous daily ET reconstruction work.

Decomposing the impacts of climate change and human activities on runoff changes in the Yangtze River Basin: Insights from regional differences and spatial correlations of multiple factors

On large scales, runoff changes are complex due to the regional differences in basin characteristics and interactions among multiple influencing factors. Accurately and quantitatively decomposing the impacts of climate change and human activities on runoff changes in large basins with significant spatial heterogeneity remains a challenge. In this paper, the fuzzy C-means (FCM) algorithm was used to identify the regional differences in hydrological processes of the Yangtze River Basin (YZRB) based on multiple factors. Then, regional Budyko equations with synthetic parameters were constructed for runoff decomposition using the hierarchical Bayesian model, considering the spatial correlations of multiple factors among basins. Results showed that 44 subbasins in the YZRB can be clustered into five clusters based on 10 factors including precipitation, temperature, precipitation seasonality, vegetation coverage, saturated hydraulic conductivity, elevation, slope, topographic wetness index, irrigation water consumption, and proportion of built-up area per unit area. From Cluster 1 to 5, P, T, IRR, and B decreased from about 1400 mm, 17 °C, 57.9 mm, and 1.59 % to about 870 mm, 12 °C, 15.6 mm, and 0.40 %, respectively, while ELEV and SLP increased from about 300 m and 3° to about 3500 m and 10°, respectively. Hierarchical Bayesian models can improve the performance of Budyko equations by better-simulating n, compared with linear regression models. Their R2, RB, and RMSE for the whole YZRB were as follows: 0.9104 versus 0.7591, 4.33 % versus 8.21 %, and 0.06 versus 0.11, respectively. Runoff decomposition from 1982 to 2018 showed that precipitation led to more than 34 % change in runoff in Cluster 2, while the influence of potential evapotranspiration on runoff changes was less than 3.00 % in each cluster. Rising temperature caused runoff to decrease by more than 7.90 % in Cluster 1, 3, and 4. In addition, precipitation seasonality, vegetation, and irrigation water consumption had different influences in different clusters. This study improves the ability of the Budyko equation to quantitatively decompose the impacts of multiple factors on regional runoff changes and provides more reasonable suggestions for water resource management.

Assessment on spatiotemporal variations for minimum water consumption of vegetation in China based on constraint line method

Driven by climate change and artificial vegetation restoration, the actual vegetation water consumption (evapotranspiration) changes dramatically, in some relatively arid areas, the contradiction between growing vegetation water demand and limited terrestrial water resources becomes more prominent in recent years. For this reason, in actual ecological restoration or adjustment projects, clarifying the maximum vegetation coverage aiming at water balance is critical to maintain normal vegetation growth and sustainable use of water resources, and quantifying the minimum water consumption of vegetation (WCVmin) is a vital path to calculate this index. Currently, how to quantify WCVmin and identify its spatiotemporal variations remains unclear. Here we put forward an approach of quantifying WCVmin by using constraint line method and water balance principle, and we calculated the WCVmin of forest, shrubland and grassland and its spatiotemporal changes across China in 1990 and 2018, respectively. The results indicate: (1) our proposed method was proved to have robust spatiotemporal applicability; (2) compared with 1990, the average WCVmin rose by 7.46% in 2018, and the area that WCVmin enhanced accounts for 59.25%, in temperate continental and alpine climate zone, this proportion reached 81.76%; (3) meanwhile, the maximum plantable area of vegetation identified based on water balance (precipitation equals to WCVmin) reduced by 3.77%, which means it is increasingly difficult to implement sustainable vegetation restoration projects in relatively arid regions across China. This study is not only conducive to identify the regions where sustainable revegetation can be implemented under the constraint of water balance, but it also contributes to illustrate the evolution of the trade-off between vegetation water consumption and terrestrial water availability under changing circumstances.

Spatio-temporal relationship between vegetation restoration and ecosystem services in the Loess Plateau of Northern Shaanxi, China

As the core region of the "Grain to Green" Program, the Loess Plateau of Northern Shaanxi became an example with the most dramatic changes in earth surface pattern and vegetation cover. Evaluating the effectiveness of vegetation restoration is important for promoting regional ecological environment. In this study, the fractional vegetation coverage (FVC) was used as the index to analyze the changes in vegetation coverage in this area. Soil conservation service, carbon sequestration service, habitat quality, and water yield were used to characterize the regional ecosystem services (ESs). The effects of FVC on ESs were analyzed based on the bivariate spatial autocorrelation model. The trade-off synergies and spatio-temporal variations of different scales of those indices were discussed. The results showed that the FVC of the study area presented a fluctuating upward trend from 2000 to 2020, with the annual average value increasing from 31.7% to 47.1%. Carbon sequestration service and soil conservation service were increased, habitat quality was stable. Water yield increased firstly and then decreased, with an overall upward trend. The ESs changes were scale-dependent. There was an obvious synergistic relationship among ESs. There was a significant spatial dependence between FVC and ESs, with some differences in the degree of correlation. FVC had the strongest impact on soil conservation, followed by carbon sequestration service. However, the increase of vegetation coverage and water consumption of forest and grass led to the negative effect of water yield reduction. In gene-ral, FVC in the Loess Plateau of Northern Shaanxi had achieved remarkable success, and the ecological environment had been significantly improved.

The Effect of Vegetative Coverage and Altitude on the Vegetation Water Consumption in the Alpine Inland River Basin of the Northeastern Qinghai–Tibet Plateau

Estimating accurately the vegetation water consumption (VWC) in the Qinghai Lake Basin (QLB) is conducive to the effective utilization and management of water resources in the QLB, which is of great significance to the construction of a national park in the QLB. We used Geographic Information System (GIS) technology and remote sensing (RS) technology based on potential evapotranspiration data to calculate the VWC in the QLB from 2000 to 2020, and analyzed the influencing factors of the VWC in the QLB from 2000 to 2020. The results showed that (1) the average value of the VWC in the QLB varied from 242.96 mm to 287.99 mm, the average value of the VWC was 267.07 mm, and the average value of the total VWC was 79.05 × 108 m3 from 2000 to 2020. (2) In terms of spatial variation of the VWC, the VWC in the QLB did not increase significantly from 2000 to 2014, however, the VWC in the QLB showed a significant increase from 2015 to 2020. (3) As the altitude gradient increases, the VWC in the QLB from 2000 to 2020 showed a significant downward trend with the increase in altitude. When the altitude increases by 100 m, the value of the VWC decreases by 13.47 mm from 2000 to 2014 and 22.8 mm from 2015 to 2020, respectively. (4) Exploring the influencing factors of the VWC in the QLB from 2000 to 2020, the results showed that the VWC was mainly affected by the average annual precipitation and normalized difference vegetation index (NDVI) from 2000 to 2014. It was mainly affected by the combined effects of annual temperature, precipitation, and vegetation coverage from 2015 to 2020. The VWC was mainly affected by the average annual temperature, precipitation, and vegetation coverage along the altitude gradient from 2000 to 2014. It was mainly affected by the average annual temperature and vegetation coverage in the QLB from 2015 to 2020. Obviously, vegetation coverage was the most important factor affecting the VWC regardless of spatial or altitude gradient variations.

亚热带岩溶区典型常绿和落叶树种的蒸腾特征及其对环境因子的响应

植物蒸腾是水循环的重要组成部分，为了解亚热带岩溶区树木的蒸腾耗水情况，探究气候和水文地质条件对植物蒸腾的影响，运用Granier热耗散探针技术，对亚热带岩溶区次生林内的常绿树种女贞（L.lucidum）和落叶树种刺槐（R.pseudoacacia）的树干液流进行了连续监测，并同步监测了气象因子及土壤含水率（SMC），探讨在不同时间尺度下两种生活型树种的蒸腾特征及其对环境因子的响应。结果表明：（1）在季节尺度下，影响两树种整树蒸腾量（ET）的主要因子为太阳辐射强度（Rs）、气温（T）和水汽压亏缺（VPD）；女贞蒸腾量（ET_L）表现为夏季（1.29 kg/h） > 春季（0.57 kg/h） > 冬季（0.15 kg/h） > 秋季（0.13 kg/h），刺槐蒸腾量（ET_R）表现为夏季（0.90 kg/h） > 春季（0.31 kg/h） > 秋季（0.16 kg/h） > 冬季（0.04 kg/h）。（2）在日尺度下，晴天两树种ET呈现出明显的单峰日变化，且主要影响因子均为T、VPD和Rs；但由于常绿和落叶树种的生理特征差异，降雨时ET_L受到抑制，而ET_R则显著提升。（3）从昼夜层面来看，两树种夜间蒸腾量不足日蒸腾总量的35%。在夜雨现象和树木生理特征的影响下，秋冬季夜间蒸腾量占比明显高于春夏季，刺槐的平均夜间蒸腾量及其占比（1.56 kg，24.1%）高于女贞（1.08 kg，13.9%）。;Plant transpiration is an important part of water cycle in ecosystem, that is, the process of water transfer from soil to atmosphere through plants. It is driven by solar radiation, air temperature, air humidity and wind speed, and also affected by soil water storage capacity. Understanding and quantifying the influence mechanism of transpiration is an important basis to explore the water consumption of vegetation and the water balance of ecosystem. However, although the climate conditions in the subtropical karst area are good, there is a drought period of 4-5 months. At the same time, plants are often affected by water stress because of the thin soil layer and low water holding capacity of soil in karst area. The study of plant transpiration characteristics helps us understand the water consumption of trees in subtropical karst areas, and is also of great significance for exploring the impact of climate and hydro-geological conditions on plant transpiration. Granier's thermal dissipation probe method was used to continuously monitor the trunk sap flow of the evergreen tree species (L.lucidum) and the deciduous tree species (R.pseudoacacia) in the secondary forest in the subtropical karst area. The meteorological factors and soil moisture content (SMC) are also monitored simultaneously. Our purpose is to analyze the transpiration characteristics of two life-form tree species and their responses to environmental factors on different time scales. The results show that:(1) at the seasonal scale, the main factors affecting the whole-tree transpiration (ET) are solar radiation intensity (Rs), air temperature (T) and vapor pressure deficiency (VPD). The transpiration of L.lucidum (ET_L) is shown as summer (1.29 kg/h) > spring (0.57 kg/h) > winter (0.15 kg/h) > autumn (0.13 kg/h), transpiration of R.pseudoacacia (ET_R) is shown as summer (0.90 kg/h) > spring (0.31 kg/h) > autumn (0.16 kg/h) > winter (0.04 kg/h). (2) On the daily scale, the ET of the two tree species shown obvious single peak curve on sunny day, and the main factors affecting transpiration are T, VPD and Rs. However, due to the differences in the physiological characteristics of evergreen and deciduous tree species, ET_L is weakened during rainfall, while ET_R is significantly increased. (3) in terms of day and night, the nocturnal transpiration of the two tree species accounts for less than 35% of the total daily transpiration on average. Affected by the phenomenon of night precipitation and the physiological characteristics of trees, the proportion of nocturnal transpiration in the autumn and winter is significantly higher than that in the spring and summer. At the same time, the average daily nocturnal transpiration and its proportion of R.pseudoacacia (1.56 kg, 24.1%) is higher than that of L.lucidum (1.08 kg, 13.9%).

Unravelling the role of vegetation on the different trends between climatic and hydrologic drought in headwater catchments of Spain

The availability of water resources is a major challenge of the Mediterranean region. Intense land use transformation has impacted the headwaters of river basins that generate most of the water resources, reducing streamflow This study analyses the evolution of hydrological and climatic drought in headwater catchments of Spain and it explores the extent to which vegetation can reinforce trends in hydrological drought severity in comparison to the evolution of cFlimatic drought severity. We have used the Standardized Precipitation Evapotranspiration Index and Standardized Streamflow Index to examine hydrological and climatic drought, respectively, and examined the changes in the frequency, magnitude, and duration of climatic and hydrologic droughts over non-perturbed headwater catchments of Spain from 1961 to 2013. We quantified vegetation changes over time in the analysed catchments and we compared the changes in the climatic and hydrological droughts with changes in vegetation coverage using Pearson’s r correlations and linear regression model. The results show that the trends toward higher frequency, duration and severity of hydrological droughts are more marked than the observed trends in climatic droughts, which can be associated to the dominant increase in vegetation coverage and activity in the study domain. Finally, it is concluded that the spatial differences observed between the trends of climatic and hydrological droughts show some relationship with the patterns of forest succession observed in recent decades. Our results stress the relevance of land transformation processes on trends in water resources availability, particularly during periods of climatic droughts in which competence between vegetation water consumption and streamflow production is much more relevant.