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1. chinaXiv:202112.00103 [pdf]

基于Catboost 的AMSR-2 半经验地表温度降尺度

李永康
Subjects: Geosciences >> Geography

以古尔班通古特沙漠为研究对象,采用2019年AMSR-2的4通道被动微波亮温及MODIS植被指数,探索Catboost算法对被动微波地表温度空间降尺度的可行性,填补古尔班通古特沙漠MYD11A1的缺失像元,为获取全天候日、夜间多层土壤温度提供数据参考。结果表明:(1)古尔班通古特沙漠日、夜间用于降尺度研究的特征向量(23.8 GHz V、36.5 GHz V、18.7 GHz H、89 GHz V、36.5-23.8 GHz V、36.5 V-18.7 GHz H、EVI、NDVI)与地表温度的相关性空间分异特征明显,显示沙漠相关性高,绿洲相关性低,且日间分异性更强;而盐矿覆盖会降低微波与地表温度相关性。(2)Catboost 4通道模型建立的被动微波亮温与地表温度间映射关系表现出鲁棒性。降尺度结果精度较高,日夜间R2分别为0.977、0.980,RMSE分别为3.69 K、2.38 K,MAE分别为2.71 K、1.70 K。(3)单通道相关性统计结果与重要性分析结果存在差异,表明特征因子相关性统计结果不能直接作为Catboost被动微波反演地表温度特征选择依据。(4)降尺度结果与站点6层土壤温度均呈极显著正相关,并随着深度的增加相关系数r 总体呈下降趋势,RMSE呈增加趋势。

submitted time 2021-12-12 From cooperative journals:《干旱区研究》 Hits51Downloads31 Comment 0

2. chinaXiv:202110.00027 [pdf]

新疆阿克苏河流域生态承载力监测及安全格局构建

杨振民; 刘新平
Subjects: Geosciences >> Geography

阿克苏河流域作为西北干旱区内陆河,生态环境极为脆弱,研究其生态安全格局对优化区 域国土空间开发保护格局,推动生产生活方式向绿色转型,促进人与自然和谐共生具有重要战略 意义。基于研究区本底特征,运用空间主成分分析法(SPCA)对阿克苏河流域 1980—2018 年生态 承载力时空演变进行评估监测,利用最小累积阻力(MCR)模型提取生态廊道及生态节点,构建生 态安全格局。研究表明:(1)阿克苏河流域生态承载力空间差异明显,以中等承载为主,生态承载 优势区呈现由中东部向西部转移趋势。(2)阿克苏河流域生态承载力呈增长趋势。近 40 a 阿克苏 河流域整体生态承载力呈上升趋势,强承载区面积不断增加,弱承载区面积呈现波动下降趋势,表 明流域环境有所改善。(3)生态源地占整体面积较少,分布较为集中。根据生态承载力评估结果, 提取生态源地 23465.21 km2,约占研究区面积的 35.61%。生态源地集中分布于流域中部地区,北部 高山地区与西南部盆地、沙漠地区分布较少。(4)利用 MCR 模型及遥感影像,将阿克苏河流域划分 为 16 个生态安全格局分区,提取生态廊道 67 条,识别生态节点 71 处,并结合生态承载力评估结果, 对流域生态空间结构提出优化建议。

submitted time 2021-10-10 From cooperative journals:《干旱区地理》 Hits3946Downloads228 Comment 0

3. chinaXiv:202106.00080 [pdf]

塔里木河生态输水条件下土地利用/覆被变化 对生态系统服务价值的影响

张帅
Subjects: Geosciences >> Geography

基于 2000—2020 年土地利用数据,采用修正后的单位面积价值当量法、生态系统服务变化 指数与探索性空间分析手段,分析了塔里木河下游自生态输水以来生态系统服务功能的时空变化特征。结果表明:(1)自 2000 年生态输水以来,塔里木河下游耕地、林地和草地面积分别增长了18.6 km2、54.7 km2 和 76.7 km2,裸地面积减少了 104.0 km2;其中耕地和林地增长面积主要分布在大西海子水库—英苏段,草地增长面积主要分布在英苏—阿拉干段和阿拉干—台特玛湖段。(2)塔里木河下游生态系统服务价值由 2000 年的42.66×109 元增长到了 2020 年的 45.86×109 元,增长了3.20×109 元,且生态系统服务价值低值土地利用类型向高值土地利用类型转化频繁。(3)塔里木河下游生态系统服务价值 Global Moran’s I 由 2000 年的 0.7552 增长到 2020 年的 0.7639,该地区生态 系统服务价值存在明显的正向空间自相关关系,且增值区主要集中分布在大西海子水库—英苏段,损失区主要分布在英苏—阿拉干段和阿拉干—台特玛湖段。塔里木河下游生态输水对该地区 生态环境修复起到了积极的作用,有效提升了该区域的生态系统服务价值。

submitted time 2021-06-17 From cooperative journals:《干旱区地理》 Hits2433Downloads482 Comment 0

4. chinaXiv:202103.00034 [pdf]

基于 FSDAF 模型的干旱区典型绿洲城市 夏季地表热岛效应时空演变研究

王爽; 王承武
Subjects: Geosciences >> Geography

全球城市化进程加快引起的干旱区绿洲城市热岛效应变化及其生态环境问题已成为当前 国内外城市气候、环境和生态等领域的研究热点之一。基于遥感热红外通道反演的地表温度 (Land surface temperature,LST)是开展城市地表热岛(Surface urban heat island,SUHI)效应监测研 究的关键参数。然而,受热红外遥感数据“时空矛盾”的制约,目前在单一星载卫星传感器下尚不 存在同时具有高时间分辨率和高空间分辨率的热红外遥感数据源,因而制约了在干旱区绿洲城市 范围内开展高精度地表热岛效应监测研究。针对上述问题,以干旱区典型绿洲城市——乌鲁木齐 市为研究区域,以 Landsat 系列影像和 MODIS 地表温度产品为基础数据源,基于 FSDAF(Flexible spatiotemporal data fusion method)时空融合模型分析了 2001—2018 年乌鲁木齐市在城市扩张背景 下夏季地表热岛效应的时空变化特征以及夏季 LST 与城市地表参数之间的关系。研究结果表明:(1)乌鲁木齐市夏季热岛强度(SUHI intensity,SUHII)在不同的郊区范围内均呈现增加的趋势。在较小的郊区范围内,SUHII1 从 2001 年的 1.24 ℃增加到了 2018 年的 2.83 ℃;在较大的郊区范围内,SUHII2 从 2001 年的 1.44 ℃增加到了 2018 年的 2.88 ℃;(2)在研究区各土地利用类型中,裸地的夏 季 LST 最高,水体最低;(3)研究区地表反照率和不透水面的增加与城市夏季 LST 升高呈正相关,而植被指数与植被覆盖度则与 LST 呈负相关关系;(4)在干旱区绿洲城市,城区内部植被面积的增 加有助于缓解城市热岛效应,而仅郊区植被的增加则会导致 SUHII 的进一步增强。

submitted time 2021-03-03 From cooperative journals:《干旱区地理》 Hits723Downloads425 Comment 0

5. chinaXiv:202101.00071 [pdf]

Damage by wind-blown sand and its control measures along the Taklimakan Desert Highway in China

LI Congjuan; WANG Yongdong; LEI Jiaqiang; XU Xinwen; WANG Shijie; FAN Jinglong; LI Shengyu
Subjects: Geosciences >> Geography

Desertification is one of the most serious environmental problems in the world, especially in the arid desert regions. Combating desertification, therefore, is an urgent task on a regional or even global scale. The Taklimakan Desert in China is the second largest mobile desert in the world and has been called the ''Dead Sea'' due to few organisms can exist in such a harsh environment. The Taklimakan Desert Highway, the longest desert highway (a total length of 446 km) across the mobile desert in the world, was built in the 1990s within the Taklimakan Desert. It has an important strategic significance regarding oil and gas resources exploration and plays a vital role in the socio-economic development of southern Xinjiang, China. However, wind-blow sand seriously damages the smoothness of the desert highway and, in this case, mechanical sand control system (including sand barrier fences and straw checkerboards) was used early in the life of the desert highway to protect the road. Unfortunately, more than 70% of the sand barrier fences and straw checkerboards have lost their functions, and the desert highway has often been buried and frequently blocked since 1999. To solve this problem, a long artificial shelterbelt with the length of 437 km was built along the desert highway since 2000. However, some potential problems still exist for the sustainable development of the desert highway, such as water shortage, strong sandstorms, extreme environmental characteristics and large maintenance costs. The study aims to provide an overview of the damages caused by wind-blown sand and the effects of sand control measures along the Taklimakan Desert Highway. Ultimately, we provide some suggestions for the biological sand control system to ensure the sustainable development of the Taklimakan Desert Highway, such as screening drought-resistant species to reduce the irrigation requirement and ensure the sound development of groundwater, screening halophytes to restore vegetation in the case of soil salinization, and planting cash crops, such as Cistanche, Wolfberry, Apocynum and other cash crops to decrease the high cost of maintenance on highways and shelterbelts.

submitted time 2021-01-22 From cooperative journals:《Journal of Arid Land》 Hits1486Downloads754 Comment 0

6. chinaXiv:202101.00045 [pdf]

Spectral parameter-based models for leaf potassium concentration estimation in Ping'ou hybrid hazelnut

ZHAO Shanchao; PAN Cunde
Subjects: Geosciences >> Geography

Ping′ou hybrid hazelnut is produced by cross cultivation and is widely cultivated in northern China with good development prospects. Based on a field experiment of fertilizer efficiency, the leaf spectral reflectance and leaf potassium (K) concentration were measured with different quantities of K fertilizer applied at four fruit growth stages (fruit setting stage, fruit rapid growth stage, fruit fat-change stage, and fruit near-maturity stage) of Ping′ou hybrid hazelnut in 2019. Spectral parameters that were significantly correlated with leaf K concentration were selected using Pearson correlation analysis, and spectral parameter estimation models of leaf K concentration were established by employing six different modelling methods (exponential function, power function, logarithmic function, linear function, quadratic function, and cubic function). The results indicated that at the fruit setting period, leaf K concentration was significantly correlated with Dy (spectra slope of yellow edge), Rg (reflectance of the green peak position), λo (red valley position), SDb (blue edge area), SDr/SDb (where SDr represents red edge area), and (SDr–SDb)/(SDr+SDb) (P<0.01). There were significant correlations of leaf K concentration with Dy, Rg, SDb, Rg/Ro (where Ro is the reflectance of the red valley position), and (Rg–Ro)/(Rg+Ro) at the fruit rapid growth stage (P<0.01). Further, significant correlations of leaf K concentration with Rg, Ro, RNIR/Green, and RNIR/Blue were obtained at the fruit fat-change period (P<0.01). Finally, leaf K concentration showed significant correlations with Dr, Rg, Ro, SDy (yellow edge area), and SDr at the fruit near-maturity stage (P<0.01). Through a cubic function analysis, regression estimation model of leaf K concentration with highest fitting degree (R2) values at the four fruit growth stages was established. The findings in this study demonstrated that it is feasible to estimate leaf K concentration of Ping′ou hybrid hazelnut at the various phenological stages of fruit development by establishing regression models between leaf K concentration and spectral parameters.

submitted time 2021-01-15 From cooperative journals:《Journal of Arid Land》 Hits1027Downloads569 Comment 0

7. chinaXiv:202010.00024 [pdf]

Relationship of species diversity between overstory trees and understory herbs along the environmental gradients in the Tianshan Wild Fruit Forests, Northwest China

CHENG,Junhui; SHI,Xiaojun; FAN,Pengrui; ZHOU,Xiaobing; SHENG,Jiandong; ZHANG,Yuanming
Subjects: Geosciences >> History of Geosciences

In forest ecosystems, interactions between overstory trees and understory herbs play an important role in driving plant species diversity. However, reported links between overstory tree and understory herb species diversity have been inconsistent, due to variations in forest types and environmental conditions. Here, we measured species richness (SR) and diversity (Shannon-Wiener (H') and Simpson's (D) indices) of overstory trees and understory herbs in the protected Tianshan Wild Fruit Forest (TWFF), Northwest China, to explore their relationships along the latitudinal, longitudinal, elevational, and climatic (current climate and paleoclimate) gradients in 2018. We found that SR, and H' and D diversity indices of overstory trees and understory herbs exhibited a unimodal pattern with increasing latitude and elevation (P<0.05) and negative associations with longitude (P<0.01). Along the climatic gradients, there were U-shaped patterns in SR, and H' and D diversity indices between trees and herbs (P<0.05). SR, and H' and D diversity indices for overstory tree species were positively associated with those for understory herbs (P<0.01). These findings indicate that overstory trees and understory herbs should be protected concurrently in the TWFF to increase effectiveness of species diversity conservation programs.

submitted time 2020-10-20 From cooperative journals:《Journal of Arid Land》 Hits2318Downloads791 Comment 0

8. chinaXiv:202006.00243 [pdf]

Community structure and carbon and nitrogen storage of sagebrush desert under grazing exclusion in Northwest China

DONG Yiqiang; SUN Zongjiu; AN Shazhou; JIANG Shasha; WEI Peng
Subjects: Geosciences >> History of Geosciences

Overgrazing is regarded as one of the key factors of vegetation and soil degradation in the arid and semi-arid regions of Northwest China. Grazing exclusion (GE) is one of the most common pathways used to restore degraded grasslands and to improve their ecosystem services. Nevertheless, there are still significant controversies concerning GE's effects on grassland diversity as well as carbon (C) and nitrogen (N) storage. It remains poorly understood in the arid desert regions, whilst being essential for the sustainable use of grassland resources. To assess the effects of GE on community characteristics and C and N storage of desert plant community in the arid desert regions, we investigated the community structure and plant biomass, as well as C and N storage of plants and soil (0–100 cm depth) in short-term GE (three years) plots and adjacent long-term freely grazing (FG) plots in the areas of sagebrush desert in Northwest China, which are important both for spring-autumn seasonal pasture and for ecological conservation. Our findings indicated that GE was beneficial to the average height, coverage and aboveground biomass (including stems, leaves and inflorescences, and litter) of desert plant community, to the species richness and importance values of subshrubs and perennial herbs, and to the biomass C and N storage of aboveground parts (P<0.05). However, GE was not beneficial to the importance values of annual herbs, root/shoot ratio and total N concentration in the 0–5 and 5–10 cm soil layers (P<0.05). Additionally, the plant density, belowground biomass, and soil organic C concentration and C storage in the 0–100 cm soil layer could not be significantly changed by short-term GE (three years). The results suggest that, although GE was not beneficial for C sequestration in the sagebrush desert ecosystem, it is an effective strategy for improving productivity, diversity, and C and N storage of plants. As a result, GE can be used to rehabilitate degraded grasslands in the arid desert regions of Northwest China.

submitted time 2020-06-22 From cooperative journals:《Journal of Arid Land》 Hits7432Downloads844 Comment 0

9. chinaXiv:202006.00113 [pdf]

叶尔羌河流域土地生态脆弱性差异评价

乌宁巴特; 刘新平; 马相平
Subjects: Geosciences >> Geography

综合评估叶尔羌河流域土地生态脆弱性,为流域重点治理、恢复绿洲生机提供决策依据和理论支持。本文以叶尔羌河流域作为研究区,获取2008—2018年各时期不同指标层数据,利用ArcGIS 10.5的栅格计算功能与自然间断分类法,综合计算研究区生态脆弱性指数,并将其划分为五种脆弱等级并表征其时空分布。研究结果表明:在空间分布上,研究区以微度、轻度脆弱区为主,面积占比分别为35.67%、33.63%,主要分布在叶尔羌河中下游冲积扇平原;中、重度脆弱区比重次之,分别占比为14.89%、12.93%,主要分布在叶尔羌河上游山地丘陵区;极度脆弱区面积占比最小,仅为2.89%,但面积亦有3 000平方公里,主要分布在叶尔羌河中下游人口密集区,对流域整体生态环境起着“木桶效应”。局部地区生态环境持续恶化,致使流域整体生态压力与生态“阈值”的平衡受到影响。在时间分布上,2008-2011年整体评价指数下降0.043 24,2010—2014年整体评价指数下降0.005 41,2014—2018年整体评价指数下降0.05686。虽然各时期土地生态脆弱指数不同程度降低,流域整体生态环境呈改善趋势,但中、重、极度脆弱区依旧分布广泛,亟需研究其分布规律,针对不同脆弱区提出具体调控对策。

submitted time 2020-06-12 From cooperative journals:《干旱区地理》 Hits8691Downloads1081 Comment 0

10. chinaXiv:202006.00125 [pdf]

配重浮球覆盖下干旱区平原水库节水率研究

韩克武; 侍克斌; 杨云鹏
Subjects: Geosciences >> Hydrology

干旱区平原水库具有水面积大、蒸发强烈等特点,本文采用直径100 mm的配重浮球来抑制平原水库的无效蒸发。以月为时间尺度,分别从浮球间孔隙造成的蒸发损失率和风浪环境中配重浮球湿润表面造成的蒸发损失率进行研究,最终建立浮球覆盖下水面蒸发抑制率和节水率计算模型。结果表明:(1)非冰冻期内,浮球间孔隙造成的蒸发损失率呈现先增大后减小,在7月达到全年最高值11.6%;冰冻期内(12月和1月),浮球间孔隙造成的蒸发损失率达到全年最低值9%。(2)相同覆盖面积下,浮球润湿率随风速的增大呈曲线增长,且覆盖面积越大,润湿率随风速的变化速率越慢。相同风速下,浮球润湿率随覆盖面积的增大呈直线下降。各覆盖面积下,单位面积节水率在7月达到最大值,分别为76.6%、78.1%、79.6%、81.2%;在4月达到最低值,分别为51.9%、54.0%、58.2%、61.3%。综上所述,配重浮球在风浪环境中稳定性好、防蒸发节水率高,是一种较为理想的防蒸发材料。

submitted time 2020-06-12 From cooperative journals:《干旱区地理》 Hits7952Downloads1099 Comment 0

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