The Distribution Patterns of Timberline and Its Response to Climate Change in the Himalayas     

SHI Peili  WU Ning  Gopal S. RAWAT 《资源与生态学报(英文版)》2020,11(4):342-348

Himalayan region represents the highest and most diverse treeline over the world. As one of the most conspicuous boundaries between montane forests and alpine vegetation, the alpine timberline attracted the interest of researchers for many decades. However, timberline in the Himalayas is understudied compared with European counterparts due to remoteness. Here we review the distribution pattern of timberline and its climatic condition, the carbon and nutrient supply mechanism for treeline formation, and treeline shift and treeline tree recruitment under climate change scenarios. Growth limitation, rather than carbon source limitation is the physiological cause of timberline under the low temperature condition. Nutrient limitation and water stress are not the direct cause of timberline formation. However, more clear local limitation factors are need to integrate in order to enable us to predict the potential impacts and changes caused by human activity and related global change in this sensitive region.  相似文献   

干旱区绿洲荒漠交错带空间贫困分异特征、减贫需求与扶贫对策研究——以新疆和田地区为例          下载免费PDF全文

李东  邢素珍  关靖云  崔春雨  陈玥彤  王玉清 《干旱区地理》2019,42(4):933-942

干旱区绿洲荒漠交错带具有自然环境恶劣、社会发展滞后、经济基础薄弱、人口素质较低、贫困现象普遍的显著特征。依据空间贫困理论、GIS空间分析技术和TOPSIS模型,研究了和田地区空间贫困等级、致贫原因及其障碍度指数,并提出了相应的扶贫对策建议。结果表明：（1）和田地区一级贫困区包括和田县（0.528 0）、民丰县（0.466 3）;二级贫困区包括皮山县（0.387 1）、于田县（0.378 8）、和田市（0.371 5）、策勒县（0.348 3）、墨玉县（0.325 7）;三级贫困区包括洛浦县（0.221 3）。（2）和田地区排序前五的减贫需求包括：生产资料（86.8%）、资金（85.5%）、住房（74.3%）、教育培训（67.0%）和饮水（64.7%）。针对研究区的空间贫困分异特征以及减贫需求,从完善公共基础设施、实施转移就业行动、发展特色优势产业、改善生产生活条件、加大教育培训力度与金融扶持力度等方面提出了相应的对策建议。  相似文献   

Changes in phytoplankton diversity and community composition along the salinity gradient of the Schelde estuary (Belgium/The Netherlands)   总被引：1，自引：0，他引：1  

Koenraad Muylaert  Koen Sabbe  Wim Vyverman 《Estuarine, Coastal and Shelf Science》2009

Phytoplankton diversity and community composition were studied along the Schelde river–estuary–coastal zone continuum during the summer of 2003. DCA analysis indicated a gradual compositional turnover of the phytoplankton community within the estuary. GAM modelling of species response curves along the estuarine gradient was used to identify taxa that had their population maximum in the river, the coastal zone or within the estuary. Taxa that had their population maximum within the estuary did not form a homogenous community but comprised species with different salinity optima and rather restricted salinity tolerances. The observed changes in community composition along the estuarine transition zone correspond more closely to an ecocline than to an ecotone model. Despite the fact that few taxa had their population maximum at or near the salinity gradient, alpha diversity did not display a minimum around the salinity gradient. This lack of a diversity minimum within the estuary was ascribed to an important contribution of taxa of riverine or coastal origin to alpha diversity within the estuary contributed. On average 55% of the alpha diversity in the estuarine samples was due to riverine or coastal taxa. Beta diversity displayed a clear maximum around the salinity gradient. For planktonic organisms which are subject to mass effects, beta diversity is probably a better indicator for the impact of the salinity gradient on diversity in estuaries than alpha diversity.  相似文献