Glacier area changes in the Nujiang-Salween River Basin over the past 45 years

Automated image classification and visual interpretation of Landsat imagery were used to extract the glacier boundary in the Nujiang-Salween River Basin(NSRB)around the years 1975,2000,and 2020.The spatiotemporal characteristics of glacier area changes in the NSRB were determined and the reasons for the spatial heterogeneity in glacier area changes were discussed,based on comparative analyses of temperature and precipitation data from meteorological stations around the NSRB.The results indicate that 1)the total glacier area in the NSRB decreased by 477.78 km^(2)(28.17%)at a rate of-0.62%/a in 1975-2020.Most shrinkage occurred at low and mid altitudes,with the most severe occurring at 5290-5540 m,accounting for 40%of the total shrinkage.Considering other river basins in China,the relative glacier area change rate in the NSRB was similar to that for typical inland river basins in northwest China but lower than that for other transboundary river basins in the southeastern Tibetan Plateau.2)These areal changes in the NSRB presented obvious regional differences.The glaciers in the Hengduan Mountains retreated significantly,followed by those in the Nyainqentanglha Mountains,with relatively low shrinkage observed in the Tanggula Mountains.The number of cold and hot spots indicating areal changes increased after 2000,along with their spatial heterogeneity.3)The glacier shrinkage rate over different time intervals was positively correlated with temperature.Thus,spatial heterogeneity of climate change effects could elucidate differences in the glacier area change rate in different regions of the NSRB.The temperature rise was determined as the primary reason for the significant glacial retreat over the past 45 years.As the significant warming trend continues,the glacier area in the NSRB is likely to shrink further.

怒江⁃萨尔温江流域植被覆盖时空变化趋势及驱动力

植被作为陆地生态系统的主要组成部分,对区域生态系统环境变化、全球碳循环和气候调节具有非常重要的作用。怒江⁃萨尔温江流域是东南亚最重要的跨境河流之一,其植被变化会影响区域生态系统和气候。研究以怒江⁃萨尔温江流域为研究区,基于2000—2021年MODIS NDVI数据,利用BFAST模型、Hurst指数以及地理探测器研究了其植被覆盖时空演变趋势和未来可持续性以及驱动因子。结果表明:(1)2000—2021年,怒江⁃萨尔温江流域植被覆盖总体呈波动上升趋势,多年平均植被覆盖度FVC(Fractional Vegetation Cover)为0.73,以高植被覆盖和较高植被覆盖为主。植被分布具有明显的空间异质性,下游和中游植被覆盖明显优于上游。(2)BFAST趋势表明,近22年怒江⁃萨尔温江流域植被覆盖改善和退化的区域面积占比分别为71.24%、28.76%,改善的区域远大于退化的区域,说明研究区植被得到较好的保护。Hurst指数显示,未来植被将持续改善和退化的区域占比分别为94.89%、2.76%。BFAST与Hurst二者叠加共耦合了17种植被覆盖的未来趋势情形,整体上未来植被呈持续改善为主,将持续改善和持续退化状态的面积占比分别为68.99%、29.09%。(3)基于最优参数的地理探测器结果表明,海拔对研究区植被覆盖分布具有宏观控制作用,影响最大,其次是气温、降水等气象因子。各区域植被覆盖影响因素又具有差异性,其中,海拔和土地利用方式对上游地区植被覆盖的影响比中游和下游区域显著;中游高山峡谷地区以海拔以及海拔差异带来的气温、降水差异对植被覆盖影响重大;下游地区以人口、GDP等人为因素影响为主。研究结果对了解研究区生态环境状况及未来变化提供科学数据支持。

云南怒江河谷新近纪砾石层与堰塞湖相沉积的发现及其意义

作者在怒江道街—惠通桥段考察研究中,填绘了道街盆地的晚新生代地质图,测量了多条河谷横剖面,不仅重新厘定了河谷中拔河150m以下的多级低阶地,而且在拔河180～380m的高度上发现了多级由磨圆良好、成分复杂的厚层冲积砾石层所组成的高阶地,及厚近100m的堰塞湖成因的砂层及其下伏厚约100m的砾石层。本文采集并测试了低阶地冲积物的OSL、U系与ESR年龄,并对湖相砂层进行了磁性地层学研究。研究表明,6级低阶地形成于中更新世以来;在组成相当于第九级阶地上部的湖相砂层剖面的磁性地层柱中,上部以正极性为主含两次短期的负极性,下部则为负极性。与标准磁性地层柱对比表明,该湖相地层形成于4.2～2.6MaBP中—晚上新世,湖相地层之下的埋藏阶地与高阶地则应形成于上新世早期至中新世晚期。据此,本文初步进行了区域地层对比,并认为:伴随青藏高原在中新世中晚期开始阶段性隆升,怒江已开始形成并下切,至上新世早期已下切至现今河床之下。