Ecological Water Conveyance Project Research Articles

Drought Stress Might Induce Sexual Spatial Segregation in Dioecious Populus euphratica-Insights from Long-Term Water Use Efficiency and Growth Rates.

P. euphratica stands as the pioneering and dominant tree within desert riparian forests in arid and semi-arid regions. The aim of our work was to reveal why dioecious P. euphratica in natural desert riparian forests in the lower Tarim River exhibits sexual spatial distribution differences combined with field investigation, tree ring techniques, isotope analysis techniques, and statistical analyses. The results showed that P. euphratica was a male-biased population, with the operational sex ratio (OSR) exhibiting spatial distribution differences to variations in drought stress resulting from groundwater depth change. The highest OSR was observed under mild drought stress (groundwater depth of 6-7 m), and it was reduced under non-drought stress (groundwater depth below 6 m) or severe drought stress (groundwater depth exceeding 7 m). As drought stress escalated, the degradation and aging of the P. euphratica forest became more pronounced. Males exhibited significantly higher growth rates and WUEi than females under mild drought stress. However, under severe drought stress, males' growth rates significantly slowed down, accompanied by significantly lower WUEi than in females. This divergence determined the sexual spatial segregation of P. euphratica in the natural desert riparian forests of the lower Tarim River. Furthermore, the current ecological water conveyance project (EWCP) in the lower Tarim River was hard to fundamentally reverse the degradation and aging of the P. euphratica forest due to inadequate population regeneration. Consequently, we advocated for an optimized ecological water conveyance mode to restore, conserve, and rejuvenate natural P. euphratica forests.

The potential risk of soil salinization on vegetation restoration by ecological water conveyance project in Qingtu Lake Wetland, northwestern China

AbstractThe Ecological Water Conveyance Project (EWCP) is an important measure to restore the degraded vegetation ecosystem in Qingtu Lake Wetland (QLW), a terminal lake wetland of an arid inland river basin in northwestern China. Although many previous studies have demonstrated the positive effect of EWCP for vegetation restoration, they have ignored the possible soil salinization by EWCP which could lead to re‐degradation of restored vegetation in QLW. Therefore, the purpose of this study is to reveal the potential risk of soil salinization on sustainable vegetation restoration in QLW. Three satellite remote sensing‐based indices (i.e., Normalized Difference Vegetation Index (NDVI), Salinity Index, and Normalized Difference Water Index) are used to indicate the spatio‐temporal evolutions of vegetation growth status, surface soil salinity, and water surface. Additionally, ground data of groundwater, soil, and ecological water volume are collected. The development of soil salinization and its risk on vegetation restoration as well as its controlling factors are subsequently studied by combining remote sensing and ground‐based data. The results indicate that the vegetation restored during the first few years of EWCP in the southwest, west, and north of QLW has degraded again due to the aggravation of soil salinization in these regions since 2019. Soil salinization was accelerated by the low groundwater depth with high mineralization and high evaporation capacity of climate without adequate inundation of ecological water. Under current ecological water management in QLW, soil salinization will intensify and vegetation will further degrade. The artificial management of ecological water in QLW has created a complex relationship among vegetation growth, soil salinization, and groundwater. This indicates the irrationality of using a fixed relationship between groundwater depth and NDVI for the computation of optimal ecological water volume in previous studies. More field monitoring of groundwater‐soil‐surface water‐plant‐atmosphere continuum and process‐based modeling of water‐salt transport and vegetation growth should be conducted in the future.

Change and Driving Factor Analysis of Eco-Environment of Typical Lakes in Arid Areas

In arid regions with scarce water resources, lakes play an extremely vital role in maintaining the ecological environment. Therefore, the Chinese government has launched an ecological water conveyance project in the Tarim River basin in Xinjiang with the aim of restoring the ecological environment of the area. In previous studies, there was no complete evaluation system used to quantify changes in the ecological environment of arid regions after ecological water conveyance. In this paper, Lake Taitema was selected as the study area, which is both a terminal lake in the Tarim River basin and an object of the ecological water conveyance project. This study utilized Landsat TM/OLI satellite remote sensing images and MODIS datasets to build a remote sensing ecological index model and systematically evaluated the changes in the ecological environment and land use types in the Taitema Lake area. A structural equation model was constructed to analyze the correlation between the area of Taitema Lake and its driving factors. The results show that over the selected 20 years, the proportion of pixels with an upward trend (Zc > 0) of the RSEI was 56.5%, while the proportion of pixels with a downward trend (Zc < 0) of the RSEI was 43.5%. The area proportion of regions with poor ecological environment quality decreased by about 40%, and the area proportions of regions with moderate, good, and excellent ecological environment quality increased by 29.7%, 10%, and 0.6%, respectively. By comparing the land use data from 2000 and 2020, the proportion of grassland increased by 6%, the proportion of water area increased by 4.4%, and the proportion of unused land decreased by 9.6%. In summary, after the implementation of the ecological water conveyance project, the ecological environment quality of the Lake Taitema area gradually improved, and ecological water conveyance was the main driving factor of the area change in Lake Taitema.

Land Use and Land Cover Change Effects on the Value of Ecosystem Services in the Konqi River Basin, China, under Ecological Water Conveyance Conditions

Basin ecosystems are vulnerable to natural resource depletion, ecological damage, and environmental pollution due to their fragile natural environment. Assessing the value of basin ecosystem services (ES) can facilitate informed decision making by policy makers and stakeholders in the context of competing resource use. The Konqi River Basin in China, an arid inland river basin, has suffered from degraded ecosystems due to overexploitation of soil and water resources. In response, the local government launched an ecological water conveyance (EWC) project in 2016 to enhance ecological restoration efforts. This paper analyzes and evaluates the value of ES in the Konqi River Basin based on land use and land cover (LULC) change characteristics before and after EWC in 2013 and 2020, respectively. Remote sensing data and related socioeconomic statistics data are used to assess a typical river basin from three unique locations in the Konqi River Basin, divided into upper and lower reaches. The results show that cropland and unused land are the most important land use types in the upper and lower reaches. The characteristics of ecosystem service value (ESV) changes in the study area are consistent with land use structure changes. The total ESV shows a decreasing trend in the upper reaches from 2013 to 2020, while the lower reaches show an increasing trend. The total ESV increases in the typical river reaches of the Konqi River Basin. Spatially, low-ESV areas are mainly located in ecologically fragile areas that are difficult to develop and use. The sensitivity indexes of the study area are all less than 1, making the results of this study credible. The Moran index shows a significant spatial correlation in the study area, indicating that the distribution characteristics of high-ESV areas are agglomerative. Hot spot areas in the upper reaches show an overall increasing trend, while in the lower reaches, former sub-hot spot areas transform into hot spot areas. Due to data limitations, this study is limited to demonstrating that the value of ES in the area changes due to a combination of EWC policies and other factors. Nevertheless, the analysis shows that EWC policies actively change the ESV of a typical river basin in Konqi. This study can provide a reference for evaluating ESV in inland river basins in the northwest arid region and a scientific basis for the rational development and utilization of water and soil resources in the study area, located in an arid and ecologically fragile area.

Changes of Lake Area, Groundwater Level and Vegetation under the Influence of Ecological Water Conveyance—A Case Study of the Tail Lake of Tarim River in China

To study the changes of water and vegetation coverage, groundwater level and plant diversity of lakes at the end of Tarim River in Northwest China, the changes of various indicators in more than 20 years (2000–2019) were analyzed through field investigation and indoor remote sensing methods. The results showed that (1): with the initiation of the development of ecological water conveyance project, water and vegetation areas increased significantly, especially the trend of vegetation areas becoming more significant, and area of sandy land decreased significantly. (2): the plant diversity increased in the early stage of ecological water conveyance, however, with the increase of lake area and groundwater level, the species composition tends to be simplified. According to the variation characteristics of species importance value in the overflow area in recent 20 years, it is found that the top communities of plant succession are Phragmites australis and Hexinia polydichotoma. (3): with the increase in the lake area, the groundwater level showed an up-lifted trend, the correlation between the two was significant, but there was a lag in the response of the groundwater level. (4): The intra-annual variations in the lake areas were considerable before and after the ecological water conveyance.

Ecological Water Demand of Taitema Lake in the Lower Reaches of the Tarim River and the Cherchen River

Taitema Lake, located in the lower reaches of the Tarim River and the Cherchen River, is one of the most important ecological barriers in Ruoqiang County. The amount of water in Taitema Lake plays an important role in maintaining a healthy cycle within the ecosystem, curbing sandstorms, and improving salinization and desertification. The aim of this study was to reasonably determine the volume of ecological water conveyance by calculating the ecological water demand. We systematically analyzed the spatial and temporal variation characteristics of Taitema Lake during 21 ecological water conveyance processes from 2000 to 2020. The results showed that the area of Taitema Lake increased at a rate of 144% per year because of the Ecological Water Conveyance Project (EWCP). The areas of water in dry, normal, and high flow years were 30.35, 57.76, and 103.5 km2, respectively. The corresponding ecological water demand was 1.58 × 108, 3.09 × 108, and 5.66 × 108 m3, respectively. We calculated that the Cherchen River and the Tarim River carried 0.87 × 108–3.11 × 108 m3 and 0.71 × 108–2.55 × 108 m3 of water, respectively, under different inflow frequencies. This study has significance as a reference for estimates of the ecological water demand of terminal lakes under the condition of artificial water transport in arid inland river basins, and provides the basis for the rational allocation of water resources in the Tarim River Basin.

Assessment of the environmental effects of ecological water conveyance over 31 years for a terminal lake in Central Asia

Inland river terminal lakes help maintain the regional ecological environment. However, terminal lakes in arid regions have shrunk dramatically over the past 50 years. We extracted the water areas of Taitema Lake in the arid region of Central Asia and calculated the fractional vegetation coverage (FVC) of the surrounding areas based on Landsat images from 1989 to 2019. We analysed the evolution and driving factors of the FVC and lake area before and after implementing an ecological water conveyance (EWC) project in 2000. The contributions of the driving factors were derived using regression analysis, and the effect coefficients were calculated with a path analysis. Results showed that before EWC (1989–1999), Taitema Lake was dry, the proportions of medium and high FVC areas were small, and FVC varied moderately. The contributions of land use and inflow water from Qarqan River to the regional FVC were 57.4% and 45.3%, respectively, and the effect coefficients of temperature and precipitation on FVC were 0.09 and 0.02, respectively. Human-dominated land-use change was the main factor affecting FVC change. After EWC (2000–2019), the water in Taitema Lake was restored, and the average annual proportions of medium and high FVC were 9.5% and 2.7% higher than the pre-EWC period, respectively. The contributions of land use and river inflow to the water area were 39.1% and 60.9%, and those to FVC were 40.7% and 59.3%, respectively. Precipitation had a slightly stronger effect on the water area and FVC than the temperature in the study area, whereas the influence of river inflow on the water area and FVC was less evident than that of the EWC. EWC can replenish lake water quickly, which is essential for improving the ecological environment of terminal lake areas.

Cumulative ecohydrological response to hydrological processes in arid basins

Abstract As a main anthropogenic hydrological process in arid areas, an ecological water conveyance project usually shows profound effects on the hydro- and bio-systems in the region. In order to explore novel methods and theories to assess cumulative effects of human activities on an ecological system, this study presents a method of cumulative ecohydrological response curves to quantitatively evaluate the effects of an ecological water conveyance project which the lag time of the cumulative response and growth rates of the cumulative effects can also be identified. With the lower Tarim River, Northwest China as a case study, we analyzed the spatiotemporal variations of the cumulative ecohydrological response in terms of two indicators, groundwater depth and vegetation coverage, based on the eighteen phases of the ecological water conveyance project. The cumulative ecohydrological response to the ecological water conveyance project was evaluated with an integrated methodology of combining the Spearman empirical statistical model, the dimidiate pixel model and the Kriging Interpolation. A cumulative ecological water conveyance volume model was further built using the Four-Parameter Logistic Model to make the cumulative response quantifiable. The cumulative quantified scheme can give a keen insight into the cumulative effects of hydrological processes under the influence of human activities. The cumulative ecohydrological response shows that: 1) the cumulative effects reflected by the positive correlation among the cumulative ecological water conveyance volume, the groundwater depth and the vegetation coverage, 2) there existed time lags in the cumulative time response, 80-day lag for groundwater and 4–7 years lag for vegetation, 3) and the cumulative spatial response of groundwater depth and vegetation was deduced. Our results suggest that the ecological water conveyance volume can be lowered to 0.5 × 108–1.5 × 108 m3 at each period. With a reasonable water conveyance strategy, the cumulative effects can reach the groundwater depth at 3.6885 m–3.7651 m and the vegetation coverage at 0.1339–0.1374 after the 5 phases of water infusion in consecutive years.

Climate change may accelerate the decline of desert riparian forest in the lower Tarim River, Northwestern China: Evidence from tree-rings of Populus euphratica

Although climate change has emerged as a major threat to biodiversity, few assessments exist of the sensitivity of desert riparian forests to climate in extremely arid plain areas. We mapped tree growth-climate correlations (time period: 1957–2015) to identify the sensitivities of Populus euphratica (P. euphratica), a dominant and important tree species in the desert riparian forest in the lower Tarim River, an extremely arid area in China, to climate change. The results indicated that groundwater depth was the key factor for controlling tree growth in the study area. In order to accurately assess sensitivity to climate change of the desert riparian forest, it was necessary to consider the effects of hydrological fluctuations on P. euphratica because the sensitivities of tree growth to precipitation and temperature depended on changes in the groundwater environment. The groundwater depth threshold to distinguish the sensitivity of climate change to P. euphratica growth was 6–7 m. Moreover, warming would accelerate desert riparian forest decline when the groundwater depth was more than 6 m because an anomalously high temperature would intensify evapotranspiration and the shortage of soil moisture during the growing season, and offset the benefits from precipitation, which would cause more drought if groundwater was not compensated by sufficient runoff. Therefore, global warming would bring great disadvantages to desert riparian forests if the current mode of the ecological water conveyance project (EWCP) continues to be implemented without a fixed time and water amount in the lower Tarim River, which could not steadily decrease and actively maintain shallow groundwater depth.

Do Ecosystem Service Value Increase and Environmental Quality Improve due to Large–Scale Ecological Water Conveyance in an Arid Region of China?

With the rapid development of the economy and the intensification of human activities, ecological systems have been degraded, especially in arid areas. The lower reaches of the Tarim River represent a typical arid area in China. Since 2000, the Chinese government has been heavily investing in the protection and restoration of the natural ecological environment of the lower reaches of the Tarim River. In this study, we aimed to resolve two key scientific issues: (1) reveal the changing characteristics of land-use in the region and identify the changes in ecosystem service value caused by these land-use changes and (2) evaluate whether the environmental quality has improved or worsened. The objective of this study is to verify whether the ecological water conveyance project promotes an increase in the ecosystem service value, with an improvement in the ecological environment, to thereby provide references for the evaluated effects of ecological water conveyance for the management of water resources. In this way, economic development can support environmental protection. Thus, the economy can be sustainably developed. Hence, based on the remote sensing data of land-use in 1990, 2000, 2010, and 2016, with the value coefficients proposed by Constanza in 1997 and changing characteristics in the land-use, the ecological service value, and environmental conditions from 1990 to 2016 were analysed. According to our results, from 1990 to 2016, the ecosystem service value has increased substantially, indicating that the benefits of ecological water conveyance were significant. The environmental condition index increased by 21.14%, showing that the ecological environment has improved. However, the environmental quality remained low. In the future, we should formulate plans for reasonable land-use that control the replacement of woodlands and grasslands with farmlands and construction. The results of this study provide a scientific basis and practical guide for restoring inland river ecosystems in arid regions.

Tree rings: A key ecological indicator for reconstruction of groundwater depth in the lower Tarim River, Northwest China

AbstractGroundwater is becoming increasingly important in extremely arid areas due to climate change and human activities. Little is known, however, regarding the long‐term dynamics of groundwater due to the lack of long‐term historical records of groundwater depth data. In this study, we investigated the relationship between hydrometeorology and tree rings of Populus euphratica (P. euphratica) and the feasibility of reconstructing historical groundwater depths from these tree rings in the lower reaches of the Tarim River, an extremely arid area in China. Tree‐ring growth of P. euphratica mainly reflected historical changes in regional water environments (including runoff and shallow groundwater), rather than climatic variables (including temperature, precipitation, relative humidity, and sunshine hours). Groundwater depth constituted the key environmental factor for directly controlling P. euphratica growth. Linear regression models using tree rings were developed to reconstruct historical changes of groundwater depths in the calendar year (January–December) and the growing season (April–August) from 1950 to 2015. Results tracked well with the main hydrological events in the study area. Our findings demonstrate that tree rings of P. euphratica are a key and effective ecological indicator for quantitatively reconstructing and elucidating historical changes of groundwater depth in the lower reaches of the Tarim River. Additionally, the suitable sampling range for establishing tree‐ring chronologies of P. euphratica and reconstructing groundwater depth is 0–300 m from the river channel in the lower Tarim River. Taking into consideration the lagged effect between runoff of the Ecological Water Conveyance Project (EWCP), decrease in groundwater and tree growth, we recommend that the optimal implementation time of ecological water conveyance is between the previous September and November in the lower Tarim River. This application will effectively improve the groundwater environment in the current year and ensure the growth of riparian trees.

Change in Spatial Distribution Patterns and Regeneration of Populus euphratica under Different Surface Soil Salinity Conditions

Ecological conservation and restoration have increasingly captured attention worldwide due to the degradation of ecosystems. As one of the most ecologically fragile areas, the Tarim River Basin, of Xinjiang, China, encountered serious decline of desert riparian forests. The Chinese government has implemented the “Ecological Water Conveyance Project” (EWCP) since 2000, protecting and restoring the dominant natural species of the desert riparian forests, i.e., Populus euphratica Oliv. The regenerative effect after the water conveyance was noteworthy. For the purpose of clarifying the mechanism of P. euphratica forest regeneration to find a better prescription for the ecological restoration works in the Tarim River Basin, we investigated the relationship between the distribution of P. euphratica and soil salinity. Experimentally evaluated the effects of surface soil salinity on P. euphratica seed germination and the influence of river flooding on the salinity of surface soils. The results showed that (1) P. euphratica trees mainly spread along the river channel within 2 km; with increasing vertical distance to the channel, the number of trees declined significantly; (2) where the salinity of the surface soil is high, there are less living P. euphratica trees; (3) the germination of P. euphratica seeds decreases with increased soil conductivity; when the soil conductivity was higher than 7 ms/cm, the germination of P. euphratica seeds was severely curtailed. (4) Flooding regimes were a pre-condition of P. euphratica restoration; they had profound effects on improving the germination of the seeds via ameliorating water conditions and reducing salinity. Our results point out that the most efficient ecological prescription for restoring and protecting desert riparian forests is to induce flooding twice yearly during June to August with 10- to 15-day durations each time. Such a plan (especially in the Tarim River Basin) should prioritize the protection of seedlings.

Hydroclimatic changes of Lake Bosten in Northwest China during the last decades

Bosten Lake, the largest inland freshwater lake in China, has experienced drastic change over the past five decades. Based on the lake water balance model and climate elasticity method, we identify annual changes in the lake’s water components during 1961–2016 and investigate its water balance. We find a complex pattern in the lake’s water: a decrease (1961–1987), a rapid increase (1988–2002), a drastic decrease (2003–2012), and a recent drastic increase (2013–2016). We also estimated the lake’s water balance, finding that the drastic changes are caused by a climate-driven regime shift coupled with human disturbance. The changes in the lake accelerated after 1987, which may have been driven by regional climate wetting. During 2003 to 2012, implementation of the ecological water conveyance project (EWCP) significantly increased the lake’s outflow, while a decreased precipitation led to an increased drought frequency. The glacier retreating trend accelerated by warming, and caused large variations in the observed lake’s changes in recent years. Furthermore, wastewater emissions may give rise to water degradation, human activity is completely changing the natural water cycle system in the Bosten Lake. Indeed, the future of Bosten Lake is largely dependent on mankind.

Variation of the floodplain forest ecosystem service value in the lower reaches of Tarim River, China

AbstractEcosystem service and human activity assessment are essential for effective natural resources allocation; however, these were seldom researched in arid region. This study used the theory proposed by Millennium Ecosystem Assessment to analyse ecosystem services provided by the floodplain forest in the lower reaches of the Tarim River. Results showed the following: (a) In the research area, the ecosystem service values of approximately US$216.78 × 108 occurring from 1972 to 2015 showed a decreasing trend; (b) the total ecosystem service values for floodplain forest and water area for all land use and land cover types accounted for 87.43% of the total value in the research area, and water supply, biodiversity protection, and waste treatment accounted for 55% of the total function values—these were the highest service values; (c) this research showed that the estimated ecosystem service values of research area were inelastic to value coefficients. This study showed that future work should allow land use and Ecological Water Conveyance Project to follow with rigorous environmental impact analyses. These analyses will be crucial to maintain the stability and sustainable development in the lower reaches of the Tarim River and also can provide references for research in the arid regions of Northwest China and Central Asia.

Vegetation responses to an ecological water conveyance project in the lower reaches of the Heihe River basin

AbstractThe lower reaches of the Heihe River basin (HHLR), which is located in arid and semiarid areas of Northwest China, has experienced severe environmental deterioration in the past several decades. The ecological water conveyance project was initiated by the Chinese Government in 2000 to address this degraded ecosystem.In this paper, runoff, vegetation changes, and the relationship between runoff and vegetation in different regions were explored after the project, normalized difference vegetation index (NDVI), as a proxy of vegetation cover. For the entire lower reaches, NDVI and runoff exhibit an increasing trend after the project. In spatial, 44% of the vegetation‐covered area is significantly increased; whereas, 37% also exhibits an insignificant increasing trend. Moreover, 15% of the vegetation‐covered area shows an insignificant decreasing trend, and 5% exhibits a significant decrease. Overall, vegetation in HHLR improved after the ecological water conveyance project. The maximum time lag for NDVI along the east river and runoff from the east river, NDVI in the Ejina Oasis and runoff from the east river and the east canal, and NDVI along the west river and runoff from the west river was 4, 4, 3, and 6 years, respectively. However, runoff from last year had a significant influence on the current year's NDVI for the east river and the east canal. Meanwhile, autumn runoff shows a significant influence on the next year's NDVI, and spring runoff is important to the current year's NDVI. So we concluded that it is reasonable to convey more water into HHLR in autumn and spring.

Impacts of ecological water conveyance on groundwater dynamics and vegetation recovery in the lower reaches of the Tarim River in northwest China.

The ecological water conveyance project (EWCP) in the lower reaches of the Tarim River provided a valuable opportunity to study hydro-ecological processes of desert riparian vegetation. Ecological effects of the EWCP were assessed at large spatial and temporal scales based on 13years of monitoring data. This study analyzed the trends in hydrological processes and the ecological effects of the EWCP. The EWCP resulted in increased groundwater storage-expressed as a general rise in the groundwater table-and improved soil moisture conditions. The change of water conditions also directly affected vegetative cover and the phenology of herbs, trees, and shrubs. Vegetative cover of herbs was most closely correlated to groundwater depth at the last year-end (R = 0.81), and trees and shrubs were most closely correlated to annual average groundwater depth (R = 0.79 and 0.66, respectively). The Normalized Difference Vegetation Index (NDVI) responded to groundwater depth on a 1-year time lag. Although the EWCP improved the NDVI, the study area is still sparsely vegetated. The main limitation of the EWCP is that it can only preserve the survival of existing vegetation, but it does not effectively promote the reproduction and regeneration of natural vegetation.

Spatial Pattern of Populus euphratica Forest Change as Affected by Water Conveyance in the Lower Tarim River

To restore declining species, including Populus euphratica and other riparian communities, in the river ecosystem of the lower Tarim River, the ecological water conveyance project (EWCP), as a part of an integrated water resource management plan, was implemented in 2000. The EWCP aims to schedule and manage the water resources in the upper reaches and transfer water to the lower reaches by a series of intermittent water deliveries. The delivered water flows along a modified river channel and nourishes riparian communities by river overflow flooding. Since it began, it has caused a fierce debate over the response of riparian vegetation to the water conveyance scheme. This study focuses on the lower Tarim River, where Populus euphratica forests have undergone watering, due to the EWCP. Twelve Landsat sensor images and one IKONOS satellite imagery acquired between 1999 and 2009 were used to monitor the change in Populus euphratica forests. Bi-temporal change detection and temporal trajectory analysis were employed to represent the spatial pattern of the forest change. Field investigations were used to analyze the driving forces behind forest change from the perspectives of anthropogenic activities and natural forces. The results showed that Populus euphratica forest have been declining in area, which implies that ecological risks have been increased during the watering process. However, forests areas have increased in the regions where the water supply is abundant, and vice versa.

Erratum to: Desert riparian forest colonization in the lower reaches of Tarim River based on remote sensing analysis

The ecological water conveyance project that pipes water from Daxihaizi reservoir to lower reaches of Tarim River has been implemented ten times since 2000. After ecological water conveyance, restoration has taken place for vegetation along the dried-up lower reaches of the Tarim River. The changes of vegetation fluctuated yearly due to ecological water conveyance. In order to reveal the detailed process of vegetation changes, remote sensing images from 1999 to 2010 were all classified individually into vegetated and non-vegetated areas using the soil-adjusted vegetation index threshold method. Then inter-annual changes of vegetation over a period of 12 years were obtained using a post-classification change detection technique. Finally, spatial–temporal changes distribution of vegetation cover and its response to ecological water conveyance were analyzed. The results indicate: (1) vegetation area increased by 8.52 % overall after ecological water conveyance. Vegetation between 2003 and 2004 increased dramatically with 45.87 % while vegetation between 2002 and 2003 decreased dramatically with 17.83 %. (2) Vegetation area gain is greater than vegetation loss during 1999–2000, 2001–2002, 2003–2004 and 2009–2010 periods. Although vegetation restoration is obvious from 1999 to 2010, vegetation loss also existed except for the periods above. It indicates that vegetation restoration fluctuated due to ecological water conveyance. (3) Spatial distribution of vegetation restoration presented “strip” distribution along the river and group shaper in the lower terrain area, while spatial distribution of vegetation loss mainly located in the upper reaches of river and area far away from the river. (4) Vegetation restoration area had a positive relative with total ecological water conveyance volume. The scheme and season of ecological water conveyance had also influenced the vegetation restoration. The vegetation change process monitoring, based on continuous remote sensing data, can provide the spatial–temporal distribution of vegetation cover in a large-scale area and scientific evidences for implementing ecological water conveyance in the lower Tarim River.

The influence of 10 years of water conveyances on groundwater and juvenile Populus euphratica of the lower Tarim River

The changes in the depth of groundwater were studied from the period before water conveyance through 2010, and the TDS of groundwater was analyzed in the lower reaches of the Tarim River during the period 2001–2010. Besides, the numbers of juvenile P. euphratica were investigated in the lower reaches of the Tarim River during the period 2001–2010. The findings indicate that: (1) the hydrological environment of the lower reaches has slowly deteriorated again; and (2) few juvenile P. euphratica were observed along the channel. These results show that the positive influence of the ecological water conveyance project on the ecosystem of the lower Tarim River should be beneficial in the long term; however, the long-term stability of the ecosystem cannot be achieved by the current water diversion scheme.

漫溢干扰过程中微地形对幼苗定居的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 漫溢干扰过程中微地形对幼苗定居的影响 DOI: 10.5846/stxb201105170646 作者: 作者单位: 中国科学院 新疆生态与地理研究所,中国科学院 新疆生态与地理研究所,新疆师范大学地理科学与旅游学院,新疆师范大学地理科学与旅游学院,新疆师范大学地理科学与旅游学院,中国科学院 新疆生态与地理研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(30970549,40971284);自治区高校青年教师培育基金项目(XJEDU2008S41) Effects of the microhabitats on the seedling emergence during the flooding disturbance Author: Affiliation: Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Geography Science and Tourism Department of Xinjiang National University,Geography Science and Tourism Department of Xinjiang National University,Geography Science and Tourism Department of Xinjiang National University,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:通过对比漫溢干扰后边坡、坡中和坡底幼苗的物种组成、密度、幼苗周边的环境条件及土壤种子库的差异来分析漫溢干扰过程中,微地形对幼苗定居的影响。结果表明:(1)微地形对幼苗物种组成和生物多样性指数的影响很大。漫溢干扰后,位于边坡、坡中和坡底幼苗的Simpson多样性指数和Mcintosh均匀度指数在0.01的水平上差异极显著,Margalef丰富度指数在0.05的水平上差异显著。(2)微地形对土壤盐分含量影响很大。方差分析的结果表明,除HCO3-和K+外,边坡、坡中和坡底的pH值、CO32-、SO42-、Ca2+和Mg2+各指标在0.01的水平上差异极显著;全盐、总盐、Cl-和Na+各指标均在0.05的水平上差异显著。(3)微地形通过改变幼苗定居的环境条件,进而影响幼苗库的物种组成、密度和生物多样性指数。微地形中,幼苗库的各种生态指标均小于对应的土壤种子库的生态指标,从坡底到坡中到边坡,除单位面积上的植被密度外,土壤种子库和幼苗库的各项生态指标的变化趋势均不同。 Abstract:The Tarim River is the longest continental river in China and charactered by its fragile ecosystem in the word. The ecological processes of the Tarim River basin have undergone great changes due to the irrational human activities over the past 50 years, especially in the lower reaches of Tarim River. Therefore, the ecological water conveyance project(EWCP) has been implemented since 2000. The EWCP is an emergency plan for conserving the natural vegetation, controlling the desertification and improving the environment in the lower reaches of Tarim River. It transfers water from the Bosten Lake, to Daxihaizi Reservoir, and finally to Taitema Lake along the water channel. There have been 12 times of watering to the lower Tarim River during the period from 2000 to 2011. After the EWCP,the natural vegetation has obvious response to the water condition change. The studies on the soil seed bank in the region are very important to restoring the degraded ecosystem in lower reaches.Soil seed bank is the potential plant population or plant community. It plays an important role in occurrence, succession, and recovery process of vegetation. The germinated species and germinated seed number in soil seed bank determine the species composition and species number of seedlings in a certain degree. Meanwhile, the topography condition in the study areas is also an important factor on influencing germination ability of soil seed bank. Micro-topography impacts the seedling species composition and distribution pattern through the spatial differences in germination ability of soil seed bank, light, water and salt conditions. This paper takes the EWCP as a case study to analyze the effects of micro-topography on the seedling emergence during the flooding disturbance by the method of variance analysis. The species composition, seedling density, environmental condition and soil seed bank in three micro-topography type of the side slope, hillside and base of slope are compared after river flooding disturbance. The study results revealed that: (1) Species composition and diversity indices of the seedling were significantly influenced by different types of the micro-topography. After overflowing disturbance, Simpson index and Mcintosh index of seedling species in three types of micro-topography are aloes highly significant at the level of 0.01, and Margalef index is significantly different at the level of 0.05.(2) There is also a great effect on soil salt in the different micro-topography. The variance analysis showed that: except for the HCO3- and K+, the value of pH, CO32-, SO42-, Ca2+ and Mg2+ in three types of micro-topography are all significantly different at the level of 0.01, and the value to total salt, soluble salt, Cl- and Na+ are significantly different at the level of 0.05. (3) Micro-topography can affect the species composition, density and diversity indices of the seedling by changing the resided seedling's microhabitat. Under the condition of the micro-topography, the values of the ecological indicators in the seedling bank were less than those in the soil seed bank. From the base slope, hillside slope to side slope, the changing trends of the ecological indicators were different between the soil seed bank and seedling bank expect for the indicator of the vegetative density..The results can better reveal the impact mechanism of river flooding on compose and construction of the plant community, which has an important significance on the degraded ecosystem restoration. Furthermore, the results have a practical reference on protecting and recovering of the natural vegetation in the study region after river flooding interference. 参考文献 相似文献 引证文献