Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： To explore the dynamic evolution of vegetation and its influencing factors in Ji County during the last 30 years, this study used Landsat images, along with meteorological, land use, and night light data. This study adopted trend, partial correlation, random forest, and residual analysis methods to explore the temporal and spatial variation-related characteristics in vegetation coverage and the influence of the climate and human factors on the vegetation changes in the County. (1) FVC in the study area demonstrated a significant upward trend from 1990 to 2020, with an annual growth rate of 0.49%, and the vegetation quality was distinctly higher. (2) The low and high rates of FVC had an obvious staggered spatial distribution. The proportion of areas with a marked enhancement in FVC was 51%, and a remarkable reduction in FVC was 7%. (3) Temperature and precipitation inhibited vegetation growth in the FVC high-value and built-up areas, but promoted vegetation cover in others. The contribution rates of climate change and human activities to vegetation dynamics were 53.43% and 46.57%, respectively, and were considered global influencing factors. When used as local variables, the relative contribution rates were reduced to 13.07% . Human activity was an essential factor affecting vegetation degradation in certain areas, such as the central and eastern parts of Jixian County, and the vegetation restoration in the west and south. This study can provide a scientific basis for the follow- up work of regional ecological restoration.
Subjects: Geosciences >> Geography submitted time 2023-06-28 Cooperative journals: 《干旱区地理》
Abstract：植被覆盖变化不仅与气候因子密切相关，而且也受人类活动的影响。目前，从省级尺度研究中国植被时空变化特征以及定量分析气候因子结合人类活动对植被覆盖影响研究仍较少。基于Google Earth Engine（GEE）平台和20002020Landsat数据及同期气候与夜间灯光数据，采用像元二分法、线性回归分析、变异系数、偏相关分析和贡献度模型等方法对中国植被覆盖度时空演变及其对气候变化和城市化的响应进行了分析。结果表明：（1）20002020年中国植被覆盖度以0.32%a-1的速率增长。植被覆盖区域以高覆盖度为主，面积占研究区域的38%，总体呈现从东南至西北递减的趋势。（2）黄土高原、云南省、西藏自治区和新疆维吾尔自治区西部植被覆盖度呈现增长趋势。植被年际波动在南部比北部、东部比西部稳定。黑龙江省植被覆盖度最高，为91.7%；新疆维吾尔自治区最低，为14.4%；宁夏回族自治区植被覆盖度以0.98%a-1的速率增长，植被得到显著改善。（3）气候因子和城市化对植被覆盖度的影响存在明显空间差异性。气温和降水量对中国北部地区植被覆盖度的影响分别为负相关和正相关，城市化主要影响经济较为发达的省份。气温是宁夏回族自治区的主要贡献因子，平均贡献度为84.3%；降水量是台湾省的主要贡献因子，平均贡献度为71.7%；城市化贡献度最大的城市为上海，平均贡献度为26.5%。
Subjects: Geosciences >> Geography submitted time 2022-12-12 Cooperative journals: 《干旱区科学》
Abstract： Vegetation growth status is an important indicator of ecological security. The Tarim River Basin is located in the inland arid region of Northwest China and has a highly fragile ecological environment. Assessing the vegetation net primary productivity (NPP) of the Tarim River Basin can provide insights into the vegetation growth variations in the region. Therefore, based on the Google Earth Engine (GEE) cloud platform, we studied the spatiotemporal variation of vegetation NPP in the Tarim River Basin (except for the eastern Gobi and Kumutag deserts) from 2001 to 2020 and analyzed the correlations between vegetation NPP and meteorological factors (air temperature and precipitation) using the Sen slope estimation method, coefficient of variation, and rescaled range analysis method. In terms of temporal characteristics, vegetation NPP in the Tarim River Basin showed an overall fluctuating upward trend from 2001 to 2020, with the smallest value of 118.99 g C/(m2•a) in 2001 and the largest value of 155.07 g C/(m2•a) in 2017. Regarding the spatial characteristics, vegetation NPP in the Tarim River Basin showed a downward trend from northwest to southeast along the outer edge of the study area. The annual average value of vegetation NPP was 133.35 g C/(m2•a), and the area with annual average vegetation NPP values greater than 100.00 g C/(m2•a) was 82,638.75 km2, accounting for 57.76% of the basin. The future trend of vegetation NPP was dominated by anti-continuity characteristic; the percentage of the area with anti-continuity characteristic was 63.57%. The area with a significant positive correlation between vegetation NPP and air temperature accounted for 53.74% of the regions that passed the significance test, while the area with a significant positive correlation between vegetation NPP and precipitation occupied 98.68% of the regions that passed the significance test. Hence, the effect of precipitation on vegetation NPP was greater than that of air temperature. The results of this study improve the understanding on the spatiotemporal variation of vegetation NPP in the Tarim River Basin and the impact of meteorological factors on vegetation NPP.
Subjects: Geosciences >> Geography submitted time 2022-11-12 Cooperative journals: 《干旱区科学》
Abstract： The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals (UN SDGs). The ecological environment of Northwest China is vulnerable to changes in climate and land use/land cover, and the changes in ecological quality in this arid region over the last two decades are not well understood. This makes it more difficult to advance the UN SDGs and develop appropriate measures at the regional level. In this study, we used the Moderate Resolution Imaging Spectroradiometer (MODIS) products to generate remote sensing ecological index (RSEI) on the Google Earth Engine (GEE) platform to examine the relationship between ecological quality and environment in Xinjiang during the last two decades (from 2000 to 2020). We analyzed a 21-year time series of the trends and spatial characteristics of ecological quality. We further assessed the importance of different environmental factors affecting ecological quality through the random forest algorithm using data from statistical yearbooks and land use products. Our results show that the RSEI constructed using the GEE platform can accurately reflect the ecological quality information in Xinjiang because the contribution of the first principal component was higher than 90.00%. The ecological quality in Xinjiang has increased significantly over the last two decades, with the northern part of this region having a better ecological quality than the southern part. The areas with slightly improved ecological quality accounted for 31.26% of the total land area of Xinjiang, whereas only 3.55% of the land area was classified as having a slightly worsen (3.16%) or worsen (0.39%) ecological quality. The vast majority of the deterioration in ecological quality mainly occurred in the barren areas Temperature, precipitation, closed shrublands, grasslands and savannas were the top five environmental factors affecting the changes in RSEI. Environmental factors were allocated different weights for different RSEI categories. In general, the recovery of ecological quality in Xinjiang has been controlled by climate and land use/land cover during the last two decades and policy-driven ecological restoration is therefore crucial. Rapid monitoring of inland ecological quality using the GEE platform is projected to aid in the advancement of the comprehensive assessment of the UN SDGs.
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Soil Science submitted time 2023-08-26 Cooperative journals: 《干旱区研究》
Abstract： Soil salinization caused by natural and anthropogenic factors is an environmental hazard that isespecially important in arid and semi-arid regions of the world. The accumulation of salts in soil is a major threatto crop production and global agriculture. Therefore, the rapid and precise detection of salt- affected lands ishighly critical for sustaining soil productivity. This paper aims to analyze the performance of the random forestalgorithm in mapping soil salinity in the Yinchuan Plain using Landsat-8 OLI, Sentinel-2A satellite images, andground-based soil salt content (SSC) measurements with the aid of the Google Earth Engine (GEE) platform. Weestimated SSC by establishing the relationship between spectral index characteristics and ground-measured soilsalt content. The results show that GEE can provide reliable data support for soil salinity prediction. The randomforest model established with Sentinel-2A as the data source performed better (R2 = 0.789, RMSE = 1.487) thanand can therefore be used for the estimation of soil salinity using high- resolution remote sensing, which canprovide theoretical support for large-scale soil salinity monitoring.
Subjects: Geosciences >> Geography submitted time 2023-03-19 Cooperative journals: 《干旱区科学》
Abstract： Eco-environmental quality is a measure of the suitability of the ecological environment for human survival and socioeconomic development. Understanding the spatial-temporal distribution and variation trend of eco-environmental quality is essential for environmental protection and ecological balance. The remote sensing ecological index (RSEI) can quickly and objectively quantify eco-environmental quality and has been extensively utilized in regional ecological environment assessment. In this paper, Moderate Resolution Imaging Spectroradiometer (MODIS) images during the growing period (July–September) from 2000 to 2020 were obtained from the Google Earth Engine (GEE) platform to calculate the RSEI in the three northern regions of China (the Three-North region). The Theil-Sen median trend method combined with the Mann-Kendall test was used to analyze the spatial-temporal variation trend of eco-environmental quality, and the Hurst exponent and the Theil-Sen median trend were superimposed to predict the future evolution trend of eco-environmental quality. In addition, ten variables from two categories of natural and anthropogenic factors were analyzed to determine the drivers of the spatial differentiation of eco-environmental quality by the geographical detector. The results showed that from 2000 to 2020, the RSEI in the Three-North region exhibited obvious regional characteristics: the RSEI values in Northwest China were generally between 0.2 and 0.4; the RSEI values in North China gradually increased from north to south, ranging from 0.2 to 0.8; and the RSEI values in Northeast China were mostly above 0.6. The average RSEI value in the Three-North region increased at an average growth rate of 0.0016/a, showing the spatial distribution characteristics of overall improvement and local degradation in eco-environmental quality, of which the areas with improved, basically stable and degraded eco-environmental quality accounted for 65.39%, 26.82% and 7.79% of the total study area, respectively. The Hurst exponent of the RSEI ranged from 0.20 to 0.76 and the future trend of eco-environmental quality was generally consistent with the trend over the past 21 years. However, the areas exhibiting an improvement trend in eco-environmental quality mainly had weak persistence, and there was a possibility of degradation in eco-environmental quality without strengthening ecological protection. Average relative humidity, accumulated precipitation and land use type were the dominant factors driving the spatial distribution of eco-environmental quality in the Three-North region, and two-factor interaction also had a greater influence on eco-environmental quality than single factors. The explanatory power of meteorological factors on the spatial distribution of eco-environmental quality was stronger than that of topographic factors. The effect of anthropogenic factors (such as population density and land use type) on eco-environmental quality gradually increased over time. This study can serve as a reference to protect the ecological environment in arid and semi-arid regions.
Subjects: Geosciences >> Geography submitted time 2024-07-11 Cooperative journals: 《干旱区地理》
Abstract：论文旨在快速提取新疆红枣种植区分布信息和种植面积，为预测产量、价格，巩固脱贫攻坚成果和助力乡村振兴提供数据支持。基于Google Earth Engine云平台，快速获取覆盖全疆的Sentinel-1雷达影像、Sentinel-2光学影像及SRTM地形数据，从中提取光谱、纹理、地形等44个特征并进行特征优选过程，在对随机森林分类器进行超参数调优后，得到新疆2021年10 m分辨率红枣种植区空间分布图，运用超像素聚类的方法对全疆主要红枣种植区域进行分类后处理及分区统计，最终得到全疆红枣种植面积。结果表明：（1）通过基于简单非迭代聚类算法进行分类处理，得到全疆红枣种植面积为4253 km2，其主要分布在南疆的阿克苏、喀什、和田地区、巴音郭楞蒙古自治州和东疆的吐鲁番市、哈密市等地。（2）对随机森林分类器进行超参数调优后，能够有效提高提取精度，基于混淆矩阵计算的平均总体分类精度为0.86，平均Kappa系数为0.82，红枣提取的生产者精度为0.87，用户精度为0.80。（3）Sentinel-1极化波段特征在红枣信息提取中占据重要地位，光谱特征和纹理特征次之。结合多源遥感数据能够快速提取新疆红枣种植区分布与面积信息，对推动该地区农业现代化、资源保护和经济发展具有重要意义。
Subjects: Geosciences >> Geography submitted time 2023-11-13 Cooperative journals: 《干旱区地理》
Abstract：作物水分生产率的准确和定量化评价是提高干旱区作物产量的基础，对缓解水资源短缺和农业可持续发展具有重要意义。以塔里木盆地北岸的渭干河-库车河绿洲（渭库绿洲）为典型区域，基于Google Earth Engine（GEE）云平台，通过建立20092020年流域SEBAL遥感蒸散发模型、棉花分布识别模型及估产模型，对流域棉花水分生产率进行评价。结果表明：（1） 渭库绿洲棉花产量从2009年的1610.10 kghm-2增长到2020年的1855.05 kghm-2，增长率为13.20%，棉花种植面积逐年向绿洲边缘延伸，棉花产量重心整体自西向东移动2485 m。（2） 棉花生长期2009年蒸散发均值为686.80 mm，2020年为738.66 mm，整体呈上升趋势，其增长率为7.02%，棉花生长期蒸散发最大值为花铃期和吐絮期，蒸散发较高值主要分布在绿洲内部与塔里木河北岸边缘。（3） 2009年水分生产率均值为0.21 kgm-3，2020年均值为0.25 kgm-3，12 a间水分生产率均值增长率为16%。在空间上，渭库绿洲水分生产率重心在红旗镇自东北向西南移动1832 m，年均移动速度为152.67 ma-1。绿洲棉花水分生产率呈现东西方向大于南北方向扩张趋势，空间分布方向趋势增强，空间格局趋向集聚化。（4） 12 a间产量的增长速度超过了蒸散发的上升速度，促使水分生产率提高。其次，水分生产率与棉花种植面积和合理的水量灌溉技术密切相关，水分生产率高值主要分布于沙雅县新垦农场和新和县桑塔木农场，由于农场规模化种植和集约化管理，促进了棉花增产、农业水资源的稳定分配和高效利用。
Subjects: Geosciences >> Hydrology submitted time 2024-06-21 Cooperative journals: 《干旱区科学》
Abstract： Understanding the dynamics of surface water area and their drivers is crucial for human survival and ecosystem stability in inland arid and semi-arid areas. This study took Gansu Province, China, a typical area with complex terrain and variable climate, as the research subject. Based on Google Earth Engine, we used Landsat data and the Open-surface Water Detection Method with Enhanced Impurity Control method to monitor the spatiotemporal dynamics of surface water area in Gansu Province from 1985 to 2022, and quantitatively analyzed the main causes of regional differences in surface water area. The findings revealed that surface water area in Gansu Province expanded by 406.88 km2 from 1985 to 2022. Seasonal surface water area exhibited significant fluctuations, while permanent surface water area showed a steady increase. Notably, terrestrial water storage exhibited a trend of first decreasing and then increasing, correlated with the dynamics of surface water area. Climate change and human activities jointly affected surface hydrological processes, with the impact of climate change being slightly higher than that of human activities. Spatially, climate change affected the 'source' of surface water to a greater extent, while human activities tended to affect the 'destination' of surface water. Challenges of surface water resources faced by inland arid and semi-arid areas like Gansu Province are multifaceted. Therefore, we summarized the surface hydrology patterns typical in inland arid and semi-arid areas and tailored surface water 'supply-demand' balance strategies. The study not only sheds light on the dynamics of surface water area in Gansu Province, but also offers valuable insights for ecological protection and surface water resource management in inland arid and semi-arid areas facing water scarcity.
Subjects: Geosciences >> Geography submitted time 2021-10-10 Cooperative journals: 《干旱区地理》
Abstract： 近年来，水资源利用超载导致新疆生产建设兵团（下称“兵团”）生产生态问题频发，科学精 准评估水资源承载现状能够为兵团社会经济发展和生态环境治理提供重要参考。兵团社会经济 用水中绝大部分为灌溉用水，因此耕地面积数据精度显著影响水资源承载现状评价结果，然而现 实中耕地面积统计数据存在一定偏差，增加了水资源承载现状评估的不确定性。基于此，通过引 入 Google Earth Engine（GEE）大数据平台和净耕地系数，精确修订耕地面积；并模拟常规灌溉、膜上 灌溉和混合灌溉 3 种灌溉用水情景，构建三生用水核算体系，对兵团及各师水资源承载现状进行精 准评估。结果表明：兵团耕地校正系数为 1.27，说明兵团耕地面积有约 27%的偏差；在与实际用水 相近的混合灌溉情景中，基于耕地面积统计数据的兵团总需水量为 106.45×108 m3，相对兵团总引 水量尚有 9.20%余量；通过 GEE 校正耕地面积后，兵团总需水量为 125.64×108 m3，超载 7.16%，且 13 个师中仅四师和十师 2 个师用水量不超载，表明灌溉用水过度占用有限的水资源量、挤占大量生态 用水，是导致兵团水资源超载和生产生态问题频发的关键。本研究实现了对兵团水资源承载现状 的科学精准评估，能够为兵团水资源利用及优化配置、区域可持续发展提供参考。
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