Subjects: Geosciences >> Geography submitted time 2023-09-19 Cooperative journals: 《干旱区地理》
Abstract： High- resolution soil salinity maps are urgently needed in arid and semi-arid regions to visualize thesubtle spatial variations in salinity distribution. These maps are crucial for guiding the development of land resource management policies and water resource management policies in salt-affected and potentially salt-affectedareas, aiming to prevent further soil degradation and ensure sustainable agricultural economic development andfood security. Based on PlanetScope imagery, vegetation spectral indices and soil salinity indices were extracted,resulting in a total of 21 variables. These variables were used as input for the Bagging algorithm to construct asoil salinity prediction model, referred to as ModelⅠ- . The max-relevance and min-redundancy (mRMR) methodwas employed to select relevant feature variables, which were then inputted into the Bagging algorithm to build asoil salinity prediction model, referred to as Model-Ⅱ. Field sampling data were used to assist in model buildingand validation. Model-Ⅰ and Model-Ⅱ were evaluated using model evaluation metrics. The results indicate thatthe prediction performance of Model-Ⅱ is better than that of Moedl-Ⅰ (mean R2=0.66, mean RMSE=18.00 dS·m-1,mean PRIQ=3.21 for the validation set), and that mRMR effectively reduces the multidimensional feature redundancy. PlanetScope images combined with the mRMR method successfully mapped high-resolution soil salinity,which provided more detailed information on the spatial distribution of soil salinity, and the results of the studypromoted the use of PlanetScope data to monitor soil salinity information.
Subjects: Geosciences >> Geography submitted time 2023-04-07 Cooperative journals: 《干旱区地理》
Abstract： Accurate monitoring of runoff from small and medium-sized rivers is of great significance for ecological stability in arid areas. However, it is difficult to accurately retrieve the flow of small and medium-sized rivers by remote sensing. Taking the Zhongfengchang river section of Kashi River in Nilka County, Xinjiang, China, as an example, this study constructed a power function relationship model between river width, water depth, and discharge based on the relationship fitting method and measured hydrological data, unmanned aerial vehicle data, and satellite data. Using the time series of satellite data, the runoff volume of the monitored river section was inferred 24 times in different periods. The results show that when the runoff rate is 0-50 m3 ·s −1 and 50-100 m3 ·s −1 , the inversion of the runoff rate based on the hydraulic geometry of the river width is optimal, with root mean square errors (RMSEs) of 7.15 m3 ·s −1 and 2.81 m3 ·s −1 , respectively; when the runoff rate is 100-200 m3 ·s −1 and > 200 m3 ·s −1 , the inversion of the hydraulic geometry based on water depth and river width is the best, with RMSEs of 13.37 m3 ·s−1 and 1.06 m3 ·s−1 , respectively. These findings provide a new method for the fine monitoring and management of runoff of small and medium-sized rivers in areas lacking hydrologic data and have high reference value for flood disaster prediction, hydropower resource development, and water ecosystem restoration.
Subjects: Geosciences >> Hydrology submitted time 2023-03-14 Cooperative journals: 《干旱区地理》
Abstract： Groundwater is important for regulating the water cycle and ecosystem in arid areas. Understanding and managing groundwater resources is the key to preventing the reduction of river baseflow, ground subsidence and water quality degradation. Therefore, this study analyzed the groundwater chemical parameters and hydrogenoxygen stable isotope characteristics of the Ebinur Lake Basin, Xinjiang, China, and explored the sources of groundwater recharge, dynamic changes of water chemical components in different regions by combining linear regression, two-terminal mixed model and GIS spatial analysis. The results showed that: (1) Different circulation processes of groundwater existed in different areas of the Ebinur Lake Basin, with the largest of hydrogen and oxygen isotopes (δ2 H and δ18O) in the middle and lower reaches of the Bortala and Jing Rivers, followed by the area around Lake Ebinur Basin, and the smallest in the upper Bortala River area. (2) Deuterium excess parameter (d-excess) parameter and hydrochemical composition of groundwater reflected different groundwater recharge mechanisms and influencing factors. Groundwater in the upper Bortala River area was mainly recharged by glacial snow melt water. The main sources of groundwater in the middle and lower reaches of the Bortala and Jing Rivers were surface water and precipitation, which were also greatly influenced by the nature of rock formations, farmland development and irrigation measures. Groundwater around Lake Ebinur Basin mainly came from snow and ice melt and precipitation. The middle and lower reaches and groundwater in the river and lake confluence areas are the key areas for pollution prevention and control and management. (3) Different hydraulic connections existed in underground aquifers. The electrical conductance (EC) of flow system I ranged from 210.00 μS·cm-1 to 2500.00 μS·cm-1 , and the d-excess ranged from 6.47‰ to 9.70‰. The EC of flow system II ranged from 141.60 μS·cm-1 to 5260.00 μS·cm-1 , and the d-excess ranged from 9.61‰ to 17.45‰. In conclusion, this study investigated the driving mechanisms of hydrogen and oxygen isotopes and water chemistry in groundwater in the Lake Ebinur Basin, which provided some theoretical reference for the rational use and scientific development of groundwater resources in the basin.
Subjects: Geosciences >> Geography submitted time 2020-01-06 Cooperative journals: 《干旱区地理》
Abstract：土壤电导率 (Electrical conductivity, EC)是评价土壤盐渍化的重要指标。通过实测新疆艾比湖湿地自然保护区土壤EC及可见光—近红外光谱数据，利用波谱响应技术模拟Landsat 8 OLI、Sentinel 2、Sentinel 3卫星的宽波段数据。构建宽波段模拟数据及其5种预处理后的三维光谱指数 (Three-dimensional spectral index, TDSI)，采用梯度提升回归树算法 (Gradient boosting regression tree, GBRT) 建立3种卫星土壤EC估算模型，并比对加入TDSI后模型精度的变化。结果表明：在不同土壤EC条件下，3种卫星具有相似的光谱趋势，均在红、近红外波段附近反射率较高；TDSI与土壤EC相关性基本均在0.4以上，最大程度保留了与土壤EC敏感度高的红、绿、蓝、近红外、短波红外波段信息；GBRT对于土壤EC估算能力表现突出，3种卫星对土壤EC的最佳预测精度R2分别为0.831、0.847、0.903，在加入TDSI后，R2分别提高至0.835、0.857、0.935，综合分析发现，Sentinel 3对土壤EC估算效果最佳 (R2=0.935，均方根误差RMSE=2.986 mS·cm-1，赤池信息准则AIC=57.500)。通过利用波谱响应技术结合TDSI深度挖掘波段间的协同信息，采用GBRT验证了不同卫星对土壤R2的估算效果，二者相结合可以有效提升模型预测精度，为干旱区土壤盐渍化定量监测与防控提供有利指导。
Subjects: Geosciences >> Geography submitted time 2019-11-15 Cooperative journals: 《干旱区地理》
Abstract：为了探讨既能保留光谱信息又能准确对土壤有机质含量进行快速检测。以新疆南部渭干河—库车绿洲内部73个土壤样点及其对应的高光谱数据为研究对象，采用小波变换与数学变换进行光谱数据预处理，分析各小波分解重构光谱在不同有机质含量与不同土壤类型下光谱曲线差异，通过相关分析确定最大小波分解层并筛选敏感波段，结合灰色关联分析与随机森林预测分类模型对各小波分解特征光谱进行重要性分析，最后基于最优特征光谱建立多元线性预测模型并进行分析。结果表明：（1） 耕作土壤与林地土壤光谱曲线波段相较盐渍土壤和荒漠土壤光谱曲线变化较为平缓，同时在水分吸收波段处，盐渍土壤光谱曲线吸收谷最深。（2） 小波变换分解光谱与土壤有机质含量的相关性随着分解层数增加呈现先减后增趋势，在第6层中，特征光谱曲线与敏感波段数量变化趋于稳定，确定为小波变换最大分解层。（3） 随机森林模型相比灰色关联分析对于各小波分解层因子的筛选符合预期，按照对土壤有机质含量影响从高到低排序为L3-(1/LgR)′、L4-(1/LgR)′、L6-(1/LgR)′、L5-(1/LgR)′、L2-(1/LgR)′、L0-1/LgR、L1-1/LgR。（4）在小波分解光谱中，中频范围特征光谱对干旱区土壤有机质含量的估测能力优于高频与低频范围特征光谱，同时基于L-MC建立的模型精度最高。研究表明：基于机器学习分类方法结合小波分解的土壤光谱有机质含量监测，可以有效的减少噪声波段干扰，并提高特征波段的分类预测精度。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：为定量描述干旱区绿洲盐渍化土壤的粒径分布特征，对38个土壤样品的粒径分布与含盐量进行测定，并基于分形理论定量表征了研究区盐渍土和非盐渍土的土壤粒径分布特征。结果表明：粉粒的体积分数占主导地位，砂粒和黏粒次之；土壤含盐量与粉粒和黏粒体积分数呈正相关，而与黏粒呈负相关；单重分形维数D值介于1.990~2.349，且与土壤黏粒和粉粒含量成正比，相关系数分别为0.81和0.64(P<0.01)，与砂粒含量呈反比，相关系数为-0.67(P<0.01)；[WTBZ]土壤粒径分布具有多重分形特征，盐渍土(含盐量≥3 g·kg-1)的粒径分布较非盐渍土(<3 g·kg-1)更广，非均匀性更强；土壤含盐量与多重分形信息维D1和D1/D0呈极显著负相关，相关系数分别为-0.265(P<0.01)和-0.283(P<0.01)，与多重分形谱谱宽呈现极显著正相关，相关系数为0.206(P<0.01)，而与D、容量维D0[WTBZ]和多重分形谱性状特性均没有显著相关性。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：以渭干河—库车河绿洲(渭—库绿洲)为研究区，采用在机器学习方面具有明显优势的随机森林回归算法，对绿洲内的4种典型植被(棉花、芦苇、杨树、大枣)叶片的叶绿素相对含量(soil and plant analyzer development, SPAD)进行估算和验证。首先基于“红边”处光谱信息丰富的哨兵2号(Sentinel-2)影像和由其衍生的一阶微分、二阶微分影像各提取23种对叶绿素敏感的宽波段光谱指数，加入3种影响植物生长的土壤参量(土壤含水量，土壤有机质，土壤电导率)作为影响叶片SPAD的特征变量，再根据以上特征变量对每种植被叶片各建立3种方案的SPAD估算模型，从而实现对绿洲内植被叶绿素的监测。结果表明：① 影像经一阶微分再提取的植被指数相比原位光谱植被指数，在SPAD估测模型中起到了更重要的作用，在随机森林算法的重要性排序中位居前列；② 4种植被叶片的SPAD估测模型都取得了不错的效果，芦苇叶片尤为显著，确定系数(R2)达到了0.926；③ 分析对比3种方案下模型预测能力，方案3(包含土壤参量)的预测能力卓越〔2.143方案1>方案2，土壤属性和模型预测结果有较强的非线性相关。Sentinel-2数据具有理想的估算绿洲植被叶绿素含量的潜力，提供了一种高效、低成本、潜在高精度的方案来估算叶绿素含量，可为干旱区绿洲农业、生态系统实现更有效的保护和管理提供参考。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-09 Cooperative journals: 《干旱区研究》
Abstract：基于艾比湖绿洲4个气象站1960—2013年逐月的气候资料，计算了干燥指数。结果表明：① 艾比湖绿洲近54 a干燥指数的均值为6.97，属于干旱地区，干燥指数呈显著下降趋势，并且持续性较强，下降幅度约为0.49·(10a)-1（P<0.05）；夏季的干燥指数最大，为9.04，冬季最小，仅为2.20。② 艾比湖绿洲全年干燥指数在1985年发生突变性减小，夏季和冬季发生突变性减小的年份为1991年和1983年，而春季和秋季不存在突变点。③ 艾比湖绿洲干燥指数的演变过程存在着7~8 a和20~21 a的周期变化，其变化的第一主周期为9 a，第二、三周期分别为21 a和5 a。④ 干燥指数对于风速的变化最为敏感，并且相对贡献率最高，而日照时数的变化最不敏感。
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2018-09-03 Cooperative journals: 《干旱区研究》
Abstract：利用新疆北部地区（下称北疆）41个气象站1961—2014年月平均气温资料，运用线性倾向率、滑动平均、基于ArcGIS的混合插值法、累积距平分析、Mann—Kendall突变检验，基于Matlab的Morlet小波分析等方法对北疆地区年及季节气温变化进行分析。结果表明：① 北疆地区年及季节平均气温出现多次冷暖波动，均呈显著增温趋势。其中，年及春、夏、秋季从20纪90年代以后增温显著，冬季20世纪80年代以后增温显著。② 北疆地区年平均气温倾向率为0.35 ℃•（10a）-1，增温幅度较大区域主要在准噶尔盆地、塔城地区及富蕴。③ 北疆地区年及四季平均气温均发生突变。其中，年、春、夏、秋季平均气温突变主要发生在20世纪90年代，冬季气温突变主要发生在70年代末。④ 北疆地区年平均气温在近54 a存在27 a主周期和14 a次周期，气温冷暖交替，周期表现具有全域性。
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