梁尔源-喜马拉雅山南坡高山树线形成机制探讨.pptVIP

梁尔源 2015.11.08;1. 林线树木生长对气候变化的响应; 基于全球尺度上林线不同温度参数的相似性 (Jobbágy and Jackson 2000; Grace et al. 2002; K?rner and Paulsen 2004), 生长限制假说 （the growth limitation hypothesis）得到广泛认可：生长季温度是高纬度和高海拔林线上树木生长的主要限制因子 (e.g., K?rner 2003; K?rner and Paulsen 2004; Wieser and Tausz 2007). 生长限制假说得到全球尺度上一系列林线树轮研究 (e.g., Payette et al. 1989; M?kinen et al. 2000; Tardif et al. 2003; Frank and Esper 2005; Luckman and Wilson 2005; Villalba et al. 1997; Vila et al. 2008; Liang et al. 2009; Salzer et al. 2009; Huang et al. 2010; Ettinger et al. 2011), 形成层活动 (Rossi et al., 2008) 和机理模型的 (Dullinger et al. 2004; Wiegand et al. 2006)支持. ;过去200年来树线的位置没有发生显著的变化，但种群密度呈持续增加的趋势。变暖向更有利于树线过渡带内的冷杉更新。;Little ice age Maximum; 青藏高原高山林线上树木的生长受温度限制，支持生长受限假说。 气候变暖已经造成林线上树木生长的增加 喜马拉雅山南坡高山林线上树木生长动态？;2. 喜马拉雅山南坡气候概括;采样点海拔：3000米左右，在最大降雨带内 树木的生长受生长季早期温度变化的影响;越高海拔处树木的生长越有可能受降水限制;Based on the fact that precipitation in the Himalayas decreases with increasing elevation above 2000–3000 m asl, we hypothesized that tree growth at upper timberlines might be more strongly limited by poor moisture availability than by low temperature.;3. 尼泊尔桦树林线野外调查;Liang et al., 2014, Ecology;Langtang valley;Scale bars in A and B are 2 mm, and in C are 0.2 mm.;降水;原因之一;原因之二;Percentage of (A) trees with locally missing rings in 2004 in different age classes,;The occurrence of locally missing rings was significantly associated with warm and dry conditions during the pre-monsoon season. Trees at the upper timberline is very thirsty under warm and dry climate conditions ;Lei et al. 2014, Climate Change;原因之三：生长季之前的降水决定了形成层开始活动的日期;Himalayan birch prefers to grow in the rain shadow area and its growh is probably limited by precipitation.;Cassiope fastigiata;青藏高原和国际上其他林线上树木的生长主要受温度限制； 喜马拉雅山南坡糙皮桦林线树木的生长主要受季风前降水的限制，是研究受降水驱动的天然林线的典型个例； 其树线种群更新、过去树线波动历史等都是值得研究的主题;Allen et al., 2015;之5：相似例子，高山香柏灌木;;干旱胁迫正威胁着这一脆弱的高山灌丛生态系统;之6：半干旱区相似研究个例，祁连山气候云杉;Liang et al. 2015, Climatic Change;;Warming-induced drought is driving the tree mortality;种群竞争或者互利非气候因素如何影响生长和生态系统