Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： As the most widespread ecosystem on Earth, grassland is vital for maintaining ecological security,sustainability, and human well-being. In this study, we used systemic methods of maximum synthesis, regressionanalysis, and partial correlation analysis to investigate the spatiotemporal dynamics of grassland and its responsesto temperature and precipitation on the northern slope of the Tianshan Mountains in Changji Hui AutonomousPrefecture, Xinjiang, from 2000 to 2020. The research was based on remote- sensed time series images (e.g.,MODIS NPP and EVI) and related auxiliary data. The results indicate a significant increase in grassland NPP andEVI from 2000 to 2020, with temporal fluctuations. However, after 2016, both NPP, and EVI declined year overyear. Over the past 20 years, the mean average NPP, and EVI of grassland vegetation were 0.095 kg C·m− 2 and0.186, respectively. In 2020, grassland NPP (0.099 kg C·m−2）and EVI (0.194) increased by 28.57% and 16.87%,respectively, compared to their values in 2000 (NPP: 0.077 kg C·m− 2; EVI: 0.166). The spatial heterogeneity ofgrassland vegetation NPP increased substantially and showed a trend toward expansion, while the spatialheterogeneity of grassland EVI increased annually. The range of variation observed during this research was0.038 kg C·m− 2 for NPP and 0.059 for EVI. Overall, the spatial distribution of grassland NPP and EVI wasgenerally coherent, but variations also existed. Grassland NPP and EVI showed an upward trend with altitude,with an elevated EVI along the oasis edge and the southern edge of the Gurbantunggut Desert. In this study, wesuggest that abundant water and heat induce the formation of vigorous layers of short- lived plants, resulting inhigher coverage than other grassland plants after withering. These short-lived plants begin their life cycle in earlyspring, when hydrothermal conditions (e.g., temperature, soil moisture, and root zone soil temperature) arefavorable, and they complete their germination, growth, fruiting, and withering phases from April to June. Thearea percentages of NPP (65.01%) and EVI (21.93%) showed a significant increasing trend on the northern slopeof Tianshan Mountains in the Changji Hui Autonomous Prefecture, Xinjiang, over the last 20 years. Theproportion of vegetation NPP and EVI in the 9 grassland types showed a significant positive correlation withprecipitation, which was much greater than that with temperature during the same period, confirming thatprecipitation is the major factor affecting grassland vegetation. Furthermore, the reactions of each grasslandvegetation type (e.g., NPP and EVI) to precipitation varied. While precipitation remained a key driver forgrassland, moderate warming, especially at high altitudes, was found to be suitable for the growth of grasslandvegetation. These findings provide theoretical references for evaluating grassland ecological health anddegradation, as well as the high-quality development of grassland on the northern slope of Tianshan Mountains inthe Changji Hui Autonomous Prefecture, Xinjiang.
Subjects: Geosciences >> Geography submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： The construction of an ecological security pattern in arid zones is conducive to promoting a dynamic balance between the supply and demand of regional ecosystem services. This study involves the Kaidu-Kongque River Basin in an arid zone and uses the InVEST model, the RWEQ model, and the Getis- Ord Gi* model to analyze the ecological supply sources, degree of land use, GDP per km2, population density, and the nighttime light index. This approach was used to analyze the ecological demand sources and determine the ecological corridors between supply and demand sources based on the minimum cumulative resistance model so as to construct an ecological security pattern of the study area. The results of the study are as follows: (1) There are 14 ecological supply source areas in the Kaidu-Kongque River Basin, accounting for 21.46% of the study area, and a total of 9 patches of key ecological demand source areas, accounting for 4.63% of the total area of the basin; 126 ecological corridors, including a total of 17 important corridors with a total length of 654.68 km; 65 ecological nodes, including 24 key ecological nodes. (2) The spatial mismatch between supply and demand of ecosystem services in Kaidu-Kongque River Basin is obvious, and the high supply area and high demand area show obvious characteristics with urban boundary as the dividing line. (3) Combining the natural geographic characteristics and the mobility of landscape ecosystem services in the study area, the resistance surface model is used to construct “two cores, two zones, three horizons, four verticals, and multiple nodes”of the Kaidu-Kongque River Basin. In conclusion, the ecological security pattern of the Kaidu-Kongque River Basin can provide a scientific reference for protecting regional ecosystem service functions and formulating sustainable development policies.
Subjects: Biology >> Ecology submitted time 2023-02-27 Cooperative journals: 《干旱区地理》
Abstract： Ecological water conveyance is an important measure in the special action of Populus euphratica forest protection, and the analysis of the effect of submerged irrigation on the restoration of P. euphratica forest is critical for evaluating the effect of ecological restoration. We select the National Nature Reserve of P. euphratica in Tarim Basin, Xinjiang, China, as the study area. Based on dense time-series remote sensing data, NDWI threshold segmentation and human-computer interaction were used to extract the overflowing surface of ecological water conveyance, and the modified maximal gradient difference model was used to retrieve the vegetation coverage of the P. euphratica forest. Geographical information system spatial analysis and regression analysis were used to dynamically monitor the ecological water conveyance since the implementation of the special action for P. euphratica forest protection in 2016 and quantitatively analyze the impact of the submerged irrigation area and frequency on the restoration of the P. euphratica forest vegetation coverage. The results are as follows: (1) The submerged irrigation area is mainly rising from the end of July to the beginning of August, reaching the maximum overflow area in September. In 2017, the area of ecological water conveyance was the largest, reaching 246.7 km2 , and the ecological water conveyance force in 2018—2021 was reduced compared with the previous two years. The smallest area in 2020 was 70.5 km2 . There is a tendency for the spatial distribution to be more in the north and less in the south and for downstream to be greater than upstream. (2) The vegetation coverage of the National Nature Reserve of P. euphratica in Tarim, increased from 18.88% to 19.61% from 2016 to 2021. The north side of the Tarim River with a greater submerged irrigation area shows an increasing trend, whereas the P. euphratica forest on the south side of the Tarim River with less ecological water conveyance still exhibits a degradation trend. (3) The restoration degree of vegetation coverage of the P. euphratica forest increased significantly with an increase in the ecological water submerged irrigation frequency. When the submerged irrigation frequency exceeded three times, the growth rate of vegetation coverage of the P. euphratica forest was approximately 0.93%·a-1 -1.11%·a-1 , which was 4-5 times higher than that of the nonecological water conveyance overflow area. This study provides a new idea for the evaluation of ecological water conveyance benefits of the P. euphratica forest and is of great significance for evaluating the effectiveness of the special action of P. euphratica forest protection and developing a more rational water transport strategy.
Subjects: Geosciences >> Hydrology submitted time 2022-12-20 Cooperative journals: 《干旱区研究》
Abstract：
Based on the satellite data, the water level and area information of Lake Issyk-Kul was extracted, and the water volume was reconstruct; combined with CRU meteorological data from 1960-2020, the temperature and precipitation observation data from 1960- 2000 at the Cholpon- Ata meteorological station and the water volume observation data into the lake, the lake water balance model was established to analyze the changing characteristics of each element of the water balance and to explore its influencing factors. The results indicated that: (1) Since 1960, the water volume of Issyk-Kul Lake has undergone a process of continuous decrease and fluctuating increase, with 1998 being the inflection point of the change; from the 1960s to the mid-1980s, the water volume into the lake decreased continuously mainly due to the influence of irrigation diversions, and then turned to an increasing trend after 1986 with the decrease of irrigation water and the increase of precipitation and glacial meltwater; precipitation in the lake area increased at a rate of 9.1 mm·(10a)-1 , and the evapotranspiration tends to increase significantly with increasing temperature and lake area. (2) Before the mid-1980s, Issyk-Kul had a negative water balance in most years, and groundwater continued to recharge the lake; since 1986, the water balance deficit of the lake gradually decreased, and since 1998, the positive balance has been dominated. (3) The interaction of water balance components such as runoff, precipitation and evaporation determines the changes in lake water volume, while climate change in the flow-producing areas and irrigation diversions in irrigation areas indirectly drive the changes in lake water volume by changing runoff; from 1960 to 1986, human activities, mainly irrigation diversions, were the dominant factor driving the changes in Issyk- Kul water volume, with a contribution of 71.6%, and since 1987 the cumulative contribution of climate change factors to changes in lake water volume exceeds 80%.
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2020-07-14 Cooperative journals: 《干旱区研究》
Abstract：荒漠河岸带植被在维护极端干旱区生态稳定起着极其重要的作用，研究干旱区荒漠河岸带植被对生态输水的响应及其变化过程，对生态保育恢复及输水政策制定具有重要意义。本文以塔里木河下游流域内的荒漠河岸带植被为研究对象，利用Landsat8 OLI、Sentinel-2A等数据构建植被覆被数据与典型监测断面植被指数时序数据，分析2013—2018年荒漠河岸带植被时空变化特征，并结合地下水位数据分析荒漠河岸带植被对生态输水的响应。结果表明：2013—2018年间，塔里木河下游植被面积呈持续的增加趋势，其中灌木面积恢复最大。胡杨和草本距离河岸较近，沿河岸带植被恢复的区域分布位于距离河道1.0km和2.5km的范围，而灌木林恢复区域在双通道输水措施和地下水上升的影响下，沿河岸11km范围内的灌木均呈现不同程度增加。通过对不同生态断面的3种主要植被的长势分析表明，当地下水埋深大于-5.75m时，塔里木河下游植被出现明显改善。
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2020-06-19 Cooperative journals: 《干旱区研究》
Abstract：利用遥感、水文、气象、统计年鉴等数据，基于水量平衡原理建立以生态耗水为主要水资源约束条件的耕地适宜规模模型，以渭干河流域为研究对象，估算1990—2017年4期耕地适宜面积并评价其开发潜力。结果表明：① 1990—2017年渭干河流域耕地面积持续增加，其转化来源以灌木林、草地为主。② 流域水源主要来自地表径流与可利用降水，流域耗水以生态耗水为主。③ 来水量、作物种植结构与节水灌溉是影响适宜耕地面积估算的主要因素。④ 1990年耕地达到相对饱和状态；2000年耕地水平不稳定，其扩张影响生态环境的平衡；随着作物种植结构调整与节水灌溉普及，2010、2017年实际耕地面积远小于其当年来水量下适宜耕地面积，未来耕地具有较大开发潜力。
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