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Quantifying land degradation in the Zoige Basin,NE Tibetan Plateau using satellite remote sensing data 被引量:12
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作者 YU Kai-feng frank lehmkuhl Dimitri FALK 《Journal of Mountain Science》 SCIE CSCD 2017年第1期77-93,共17页
Considerable efforts have been dedicated to desertification research in the arid and semi-arid drylands of central Asia. However,there are few quantitative studies in conjunction with proper qualitative evaluation con... Considerable efforts have been dedicated to desertification research in the arid and semi-arid drylands of central Asia. However,there are few quantitative studies in conjunction with proper qualitative evaluation concerning land degradation and aeolian activity in the alpine realm. In this study,spectral information from two Landsat-5 TM scenes(04.08.1994 and 28.07.2009,respectively) was combined with reference information obtained in the field to run supervised classifications of eight landscape types for both time steps. Subsequently,the temporal and spatial patterns of the alpine wetlands/grasslands evolutions in the Zoige Basin were quantified and assessed based on these two classification maps. The most conspicuous change is the sharp increase of ~627 km^2 degraded meadow. Concerning other land-covers,shallow wetland increases ~107 km^2 and aeolian sediments(mobile dunes and sand sheets) have an increase of ~30 km^2. Considering the deterioration,an obvious decrease of ~440 km^2 degraded wetland can be observed. Likewise,decrease of deep wetland(~78 km^2),humid meadow(~80 km^2) and undisturbed meadow(~88 km^2) were determined. These entire evolution matrixes undoubtedly hint a deteriorating tendency of the Zoige Basin ecosystem,which is characterized by significantly declined proportion of intact wetlands,meadow,rangeland and a considerable increase ofdegraded meadow and larger areas of mobile dunes. In particular,not only temporal alteration of the landcover categories,the spatial and topographical characteristics of the land degradation also deserves more attention. In the alpine rangelands,the higher terraces of the river channels along with their slopes are more liable to the degradation and desertification. This tendency has significantly impeded the nomadic and agriculture activities. The set of anthropozoogenic factors encompassing enclosures,overgrazing and trampling,rodent damaging and exceedingly ditching in the wetlands are assumed to be the main controlling mechanisms for the landscape degradation. A suite of strict protection policies is urgent and indispensable for self-regulation and restoration of the alpine meadow ecosystem. Controlling the size of livestock,less ditching in the rangeland,and the launching of a more strict nature reserve management by adjacent Ruoergai,Maqu and Hongyuan Counties would be practical and efficacious in achieving these objectives. 展开更多
关键词 Alpine ecosystem Wetlands Degradation Desertification Zoige Basin Driving mechanisms
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末次盛冰期和全新世大暖期中国北方沙地古气候定量重建初探 被引量:18
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作者 俞凯峰 鹿化煜 +1 位作者 frank lehmkuhl Veit Nottebaum 《第四纪研究》 CAS CSCD 北大核心 2013年第2期293-302,共10页
中国北方典型沙地处于东亚季风边缘区半干旱气候带,对气候变化响应敏感。本文对已有的该区域古气候记录文献资料进行整理分析和评估,对末次盛冰期与全新世大暖期两个特征时间段的古温度与古降雨量空间格局进行定量化重建,获得了其分... 中国北方典型沙地处于东亚季风边缘区半干旱气候带,对气候变化响应敏感。本文对已有的该区域古气候记录文献资料进行整理分析和评估,对末次盛冰期与全新世大暖期两个特征时间段的古温度与古降雨量空间格局进行定量化重建,获得了其分布特征。结果表明,在末次盛冰期(约26—16ka)温度降低了5—11oc,变率为60%~200%,降温极值在黄土高原南缘;降雨量减少180~350mm,变率为50%左右,东北地区降雨量变化不大。在全新世大暖期(约9~5ka),温度升高了1.0—3.5℃,变率为20%-130%;降雨量增加了30~400mm,变率为10%-120%,其中存在一些需剔除的奇异点,从东部沿海向西北内陆降雨量增幅有加大趋势。上述结果为进一步探讨中国北方干旱-半干旱区古气候变化机理、检验东亚季风区古气候数值模拟结果等提供了定量化数据。 展开更多
关键词 末次盛冰期 全新世大暖期 中国北方沙地 古气候定量重建
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