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1. chinaXiv:202109.00022 [pdf]

乌鲁木齐市生态环境遥感评价及驱动因子分析

排日海·合力力
Subjects: Geosciences >> Geography

生态环境质量评估对于区域社会经济的可持续发展至关重要。以新疆乌鲁木齐市为研究区,通过对2000年、2010年和2019年3期Landsat系列数据进行预处理,利用主成分分析法构建遥感生态指数(Remote Sensing Eco?logical Index, RSEI),使用地理探测器中单因子分析和多因子交互作用分析法对RSEI的8个影响因子(人口密度、土地利用类型、海拔高度、经济密度、绿度、湿度、热度和干度)进行影响程度的定量探测,进而揭示出影响研究区生态环境质量的主导因素。结果表明:(1)2000年、2010年和2019年乌鲁木齐市RSEI均值分别为0.21、0.21、0.23呈增加趋势,研究期内乌鲁木齐市生态变好的面积大于变差的面积,说明乌鲁木齐市的生态环境质量处于转好的状态;(2)近20 a研究区8个影响因子中单因子热度指标对RSEI的空间分异特征解释力最强;(3)研究区生态环境的空间分布特征是多种影响因子共同交互作用的结果,在考虑多因子交互作用情景下人口密度,绿度指标和干度指标是区域生态环境质量状况的主要影响因素和关键驱动力。评价区域生态环境质量,了解生态环境状况及掌握其变化规律,不仅有利于促进区域经济可持续发展,而且对于城市生态文明建设具有重要的现实意义和参考价值。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits2380Downloads23 Comment 0

2. chinaXiv:202109.00024 [pdf]

哈萨克斯坦首都努尔苏丹人工林健康评价

闫晋升
Subjects: Geosciences >> Geography

通过分析努尔苏丹不同人工林,筛选健康综合评价指标,建立健康综合评价模型,为努尔苏丹及其周边人工林提供健康综合评价理论基础。调查努尔苏丹25块人工林样地和2块天然林样地,选取林下植物Shannon-Wie?ner指数(X1)、Pielou指数(X2)、Simpson指数(X3)、林分空间综合结构综合指数(X4)、土壤有机质(X5)、全氮(X6)、全磷(X7)、pH(X8)、质量含水量(X9)、林木平均株高(X10)、平均胸径(X11)、平均枝下高(X12)、平均冠幅(X13)和林下更新(X14)共14个指标,采用因子分析、聚类分析、判别分析和逐步回归分析等多元统计分析法,对努尔苏丹人工林健康状况开展综合评价。通过因子分析将14个单项指标转换为4个相互独立的综合指标,其贡献率分别为30.482%、24.374%、19.711%和8.646%,代表了全部数据83.212%的信息量。结合因子得分系数矩阵与各因子权重得到健康综合得分值。对健康综合得分值进行聚类分析,将选择的样地划分为5类,优质健康(Ⅰ)、良好健康(Ⅱ)、一般健康(Ⅲ)、亚健康(Ⅳ)和不健康(Ⅴ)。使用判别分析验证聚类分析的效果,其自身验证与交叉验证的准确率分别为100%、85.185%。采取逐步回归分析建立努尔苏丹人工林健康评价最优数学模型,H= 0 + 0.293X13 +0.186X5 + 0.079X3 + 0.100X2 + 0.038X7(R2=0.987),筛选出5个判断人工林健康状况的指标,分别为平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷。平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷可作为判断努尔苏丹人工林健康状况的指标,可在相同条件下测定这5项指标,计算健康综合评价值并预测其健康状况。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits27Downloads18 Comment 0

3. chinaXiv:202109.00025 [pdf]

基于VSD的近20 a 来浑善达克沙地生态脆弱性变化研究

陈臻琦
Subjects: Geosciences >> Geography

如何协调区域社会经济和人口、资源环境发展,已成为生态环境建设面临的紧迫任务,识别特定地区的脆弱性则是实现有效生态系统管理的前提。以京津风沙源——浑善达克沙地为研究区,采用“暴露-敏感-适应”(VSD)模型建立评价指标体系,结合Moran’s I 指数与主成分分析,对2000—2019年该沙地生态脆弱性进行评价和驱动机制分析。结果表明:浑善达克沙地生态脆弱性20 a间呈现增加的趋势;其生态脆弱性空间上呈集聚现象,表现为西部高-高聚集、东部低-低聚集的分布格局,且具有明显的空间相关性;生态脆弱性的时空分布的异质性是由不同程度的人类活动与气候因素的叠加效应造成的。该研究为浑善达克沙地的生态建设和生态恢复提供理论依据,并提出因地制宜的治理建议和措施。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits14Downloads8 Comment 0

4. chinaXiv:202109.00026 [pdf]

巴尔喀什湖流域土地利用/覆被变化过程与趋势

刘婉如
Subjects: Geosciences >> Geography

巴尔喀什湖流域是跨越中国新疆(境内)和哈萨克斯坦(境外)的重要流域。利用1970s、2005年和2015年3期土地利用/土地覆被(Land Use and Land Cover, LULC)数据与马尔科夫模型等方法,分析1972年流域内最大的水利工程卡普恰盖水库建成和前苏联解体以来流域LULC变化过程和趋势,并对比流域境内外差异,为该地区土地资源管理及生态环境保护提供依据。结果表明:巴尔喀什湖流域LULC变化呈现出耕地和林地面积先减后增(总体增加)、水域和未利用地面积先增后减(总体减少)、草地和城乡建设用地面积持续增加的变化趋势。这表明后期LULC变化对整个研究期LULC变化影响更大。以上变化以双向转换为主,因此,整个研究期内全流域变化过程始终处于平衡状态。境内外LULC类型结构和变化过程均不相同,境内分配比境外均匀,单一类型和区域LULC变化趋势与状态指数均表明境内LULC类型变化过程比境外稳定,但由于境外面积占全流域86%,主导了全流域LULC类型结构和变化过程。全流域在研究期内始终处于平衡状态。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits19Downloads11 Comment 0

5. chinaXiv:202109.00011 [pdf]

Effects of water and nitrogen on growth and relative competitive ability of introduced versus native C4 grass species in the semi-arid Loess Plateau of China

DING Wenli; XU Weizhou; GAO Zhijuan; XU Bingcheng
Subjects: Geosciences >> Geography

Switchgrass is an introduced C4 grass in the semi-arid Loess Plateau of China, but there is a lack of information to assess its ecological invasive risk. In this study, Old World bluestems (native C4 grass) and switchgrass were sowed at five mixture ratios (8:0, 6:2, 4:4, 2:6 and 0:8) under two soil water levels (80% field capacity (FC) and 40% FC) and two nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) in a pot experiment in 2012. Biomass, root morphological traits and relative competitive abilities of these two species were analyzed. Results showed that biomass of both species was significantly greater under 80% FC or N fertilization, and switchgrass had a relatively larger root: shoot ratio (RSR). Total root length (TRL) and root surface area (RSA) of switchgrass were significantly higher under 80% FC irrespective of N treatment, while those of Old World bluestems were only significantly higher under N fertilization. N had no significant effect on TRL and RSA of switchgrass, while RSA of Old World bluestems significantly increased under 80% FC and N fertilization. Under 40% FC and N0-unfertilized treatment, the aggressivity of Old World bluestems was larger than zero at 2:6 and 4:4 mixture ratios of two species, whereas it was close to zero at 6:2 mixture ratio. Root competitive ability of switchgrass significantly increased under 80% FC or N fertilization. The aggressivity of Old World bluestems was negative at 6:2 mixture ratio under 80% FC and N fertilization, while it was positive at 2:6 mixture ratio. Switchgrass may become more aggressive when N deposition or rainfall increases, while a proper mixture ratio with appropriate water and N management could help with grassland management in the semi-arid Loess Plateau.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2480Downloads57 Comment 0

6. chinaXiv:202109.00012 [pdf]

Spatiotemporal variations of evapotranspiration and reference crop water requirement over 1957–2016 in Iran based on CRU TS gridded dataset

Brian COLLINS; Hadi RAMEZANI ETEDALI; Ameneh TAVAKOL; Abbas KAVIANI
Subjects: Geosciences >> Geography

Agriculture needs to produce more food to feed the growing population in the 21st century. It makes the reference crop water requirement (WREQ) a major challenge especially in regions with limited water and high water demand. Iran, with large climatic variability, is experiencing a serious water crisis due to limited water resources and inefficient agriculture. In order to overcome the issue of uneven distribution of weather stations, gridded Climatic Research Unit (CRU) data was applied to analyze the changes in potential evapotranspiration (PET), effective precipitation (EFFPRE) and WREQ. Validation of data using in situ observation showed an acceptable performance of CRU in Iran. Changes in PET, EFFPRE and WREQ were analyzed in two 30-a periods 1957–1986 and 1987–2016. Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast, more significant in summer and spring. However, EFFPRE decreased in the southeast, northeast, and northwest, especially in winter and spring. Analysis of annual trends revealed an upward trend in PET (14.32 mm/decade) and WREQ (25.50 mm/decade), but a downward trend in EFFPRE (–11.8 mm/decade) over the second period. Changes in PET, EFFPRE and WREQ in winter have the impact on the annual trend. Among climate variables, WREQ showed a significant correlation (r=0.59) with minimum temperature. The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran. With all changes in PET and WREQ, immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2571Downloads67 Comment 0

7. chinaXiv:202109.00013 [pdf]

Synergistic effects of multiple driving factors on the runoff variations in the Yellow River Basin, China

WANG Junjie; SHI Bing; ZHAO Enjin; CHEN Xuguang; YANG Shaopeng
Subjects: Geosciences >> Geography

River runoff plays an important role in watershed ecosystems and human survival, and it is controlled by multiple environmental factors. However, the synergistic effects of various large-scale circulation factors and meteorological factors on the runoff on different time-frequency scales have rarely been explored. In light of this, the underlying mechanism of the synergistic effects of the different environmental factors on the runoff variations was investigated in the Yellow River Basin of China during the period 1950–2019 using the bivariate wavelet coherence (WTC) and multiple wavelet coherence (MWC) methods. First, the continuous wavelet transform (CWT) method was used to analyze the multiscale characteristics of the runoff. The results of the CWT indicate that the runoff exhibited significant continuous or discontinuous annual and semiannual oscillations during the study period. Scattered inter-annual time scales were also observed for the runoff in the Yellow River Basin. The meteorological factors better explained the runoff variations on seasonal and annual time scales. The average wavelet coherence (AWC) and the percent area of the significant coherence (PASC) between the runoff and individual meteorological factors were 0.454 and 19.89%, respectively. The circulation factors mainly regulated the runoff on the inter-annual and decadal time scales with more complicated phase relationships due to their indirect effects on the runoff. The AWC and PASC between the runoff and individual circulation factors were 0.359 and 7.31%, respectively. The MWC analysis revealed that the synergistic effects of multiple factors should be taken into consideration to explain the multiscale characteristic variations of the runoff. The AWC or MWC ranges were 0.320–0.560, 0.617–0.755, and 0.819–0.884 for the combinations of one, two, and three circulation and meteorological factors, respectively. The PASC ranges were 3.53%–33.77%, 12.93%–36.90%, and 20.67%–39.34% for the combinations one, two, and three driving factors, respectively. The combinations of precipitation, evapotranspiration (or the number of rainy days), and the Arctic Oscillation performed well in explaining the variability in the runoff on all time scales, and the average MWC and PASC were 0.847 and 28.79%, respectively. These findings are of great significance for improving our understanding of hydro-climate interactions and water resources prediction in the Yellow River Basin.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2207Downloads299 Comment 0

8. chinaXiv:202109.00014 [pdf]

Spatial-temporal variations of ecological vulnerability in the Tarim River Basin, Northwest China

BAI Jie; LI Junli; BAO Anmin; CHANG Cun
Subjects: Geosciences >> Geography

As the largest inland river basin of China, the Tarim River Basin (TRB), known for its various natural resources and fragile environment, has an increased risk of ecological crisis due to the intensive exploitation and utilization of water and land resources. Since the Ecological Water Diversion Project (EWDP), which was implemented in 2001 to save endangered desert vegetation, there has been growing evidence of ecological improvement in local regions, but few studies have performed a comprehensive ecological vulnerability assessment of the whole TRB. This study established an evaluation framework integrating the analytic hierarchy process (AHP) and entropy method to estimate the ecological vulnerability of the TRB covering climatic, ecological, and socioeconomic indicators during 2000–2017. Based on the geographical detector model, the importance of ten driving factors on the spatial-temporal variations of ecological vulnerability was explored. The results showed that the ecosystem of the TRB was fragile, with more than half of the area (57.27%) dominated by very heavy and heavy grades of ecological vulnerability, and 28.40% of the area had potential and light grades of ecological vulnerability. The light grade of ecological vulnerability was distributed in the northern regions (Aksu River and Weigan River catchments) and western regions (Kashgar River and Yarkant River catchments), while the heavy grade was located in the southern regions (Kunlun Mountains and Qarqan River catchments) and the Mainstream catchment. The ecosystems in the western and northern regions were less vulnerable than those in the southern and eastern regions. From 2000 to 2017, the overall improvement in ecological vulnerability in the whole TRB showed that the areas with great ecological improvement increased by 46.11%, while the areas with ecological degradation decreased by 9.64%. The vegetation cover and potential evapotranspiration (PET) were the obvious driving factors, explaining 57.56% and 21.55% of the changes in ecological vulnerability across the TRB, respectively. In terms of ecological vulnerability grade changes, obvious spatial differences were observed in the upper, middle, and lower reaches of the TRB due to the different vegetation and hydrothermal conditions. The alpine source region of the TRB showed obvious ecological improvement due to increased precipitation and temperature, but the alpine meadow of the Kaidu River catchment in the Middle Tianshan Mountains experienced degradation associated with overgrazing and local drought. The improved agricultural management technologies had positive effects on farmland ecological improvement, while the desert vegetation in oasis-desert ecotones showed a decreasing trend as a result of cropland reclamation and intensive drought. The desert riparian vegetation in the lower reaches of the Tarim River was greatly improved due to the implementation of the EWDP, which has been active for tens of years. These results provide comprehensive knowledge about ecological processes and mechanisms in the whole TRB and help to develop environmental restoration measures based on different ecological vulnerability grades in each sub-catchment.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2462Downloads60 Comment 0

9. chinaXiv:202109.00015 [pdf]

Spatial-temporal variations of ecological vulnerability in the Tarim River Basin, Northwest China

BAI Jie; LI Junli; BAO Anmin; CHANG Cun
Subjects: Geosciences >> Geography

As the largest inland river basin of China, the Tarim River Basin (TRB), known for its various natural resources and fragile environment, has an increased risk of ecological crisis due to the intensive exploitation and utilization of water and land resources. Since the Ecological Water Diversion Project (EWDP), which was implemented in 2001 to save endangered desert vegetation, there has been growing evidence of ecological improvement in local regions, but few studies have performed a comprehensive ecological vulnerability assessment of the whole TRB. This study established an evaluation framework integrating the analytic hierarchy process (AHP) and entropy method to estimate the ecological vulnerability of the TRB covering climatic, ecological, and socioeconomic indicators during 2000–2017. Based on the geographical detector model, the importance of ten driving factors on the spatial-temporal variations of ecological vulnerability was explored. The results showed that the ecosystem of the TRB was fragile, with more than half of the area (57.27%) dominated by very heavy and heavy grades of ecological vulnerability, and 28.40% of the area had potential and light grades of ecological vulnerability. The light grade of ecological vulnerability was distributed in the northern regions (Aksu River and Weigan River catchments) and western regions (Kashgar River and Yarkant River catchments), while the heavy grade was located in the southern regions (Kunlun Mountains and Qarqan River catchments) and the Mainstream catchment. The ecosystems in the western and northern regions were less vulnerable than those in the southern and eastern regions. From 2000 to 2017, the overall improvement in ecological vulnerability in the whole TRB showed that the areas with great ecological improvement increased by 46.11%, while the areas with ecological degradation decreased by 9.64%. The vegetation cover and potential evapotranspiration (PET) were the obvious driving factors, explaining 57.56% and 21.55% of the changes in ecological vulnerability across the TRB, respectively. In terms of ecological vulnerability grade changes, obvious spatial differences were observed in the upper, middle, and lower reaches of the TRB due to the different vegetation and hydrothermal conditions. The alpine source region of the TRB showed obvious ecological improvement due to increased precipitation and temperature, but the alpine meadow of the Kaidu River catchment in the Middle Tianshan Mountains experienced degradation associated with overgrazing and local drought. The improved agricultural management technologies had positive effects on farmland ecological improvement, while the desert vegetation in oasis-desert ecotones showed a decreasing trend as a result of cropland reclamation and intensive drought. The desert riparian vegetation in the lower reaches of the Tarim River was greatly improved due to the implementation of the EWDP, which has been active for tens of years. These results provide comprehensive knowledge about ecological processes and mechanisms in the whole TRB and help to develop environmental restoration measures based on different ecological vulnerability grades in each sub-catchment.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits1816Downloads43 Comment 0

10. chinaXiv:202109.00016 [pdf]

Mathematical and statistical modeling of morphometric and planar parameters of barchans in Pashoeyeh Erg in the west of Lut Desert, Iran

Hossein GHAZANFARPOUR; Mohsen POURKHOSRAVANI; Sayed H MOUSAVI; Ali MEHRABI
Subjects: Geosciences >> Geography

Barchan dunes are among the most common accumulative phenomena made by wind erosion, which are usually formed in regions where the prevailing wind direction is almost constant throughout the year and there is not enough sand to completely cover the land surface. Barchans are among the most common windy landscapes in Pashoueyeh Erg in the west of Lut Desert, Iran. This study aims to elaborate on morphological properties of barchans in this region using mathematical and statistical models. The results of these methods are very important in investigating barchan shapes and identifying their behavior. Barchan shapes were mathematically modeled by simulating them in the coordinate system through nonlinear parabolic equations, so that two separate equations were calculated for barchan windward and slip-face parabolas. The type and intensity of relationships between barchan morphology and mathematical parameters were determined by the statistical modeling. The results indicated that the existing relationships followed the power correlation with the maximum coefficient of determination and minimum error of estimate. Combining the above two methods is a powerful basis for stimulating barchans in virtual and laboratory environments. The most important result of this study is to convert the mathematical and statistical models of barchan morphology to each other. Focal length is one of the most important parameters of barchan parabolas, suggesting different states of barchans in comparison with each other. As the barchan's focal length decreases, its opening becomes narrower, and the divergence of the barchan's horns reduces. Barchans with longer focal length have greater width, dimensions, and volume. In general, identifying and estimating the morphometric and planar parameters of barchans is effective in how they move, how much they move, and how they behave in the environment. These cases play an important role in the management of desert areas.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits1780Downloads37 Comment 0

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