Synergistic effects of past historical logging and drought on the decline of Pyrenean silver fir forests     

Jesús Julio Camarero  Christof BiglerJuan Carlos Linares  Eustaquio Gil-Pelegrín 《Forest Ecology and Management》2011,262(5):759-769

The causal factors and effects of forest declines are not well understood in temperate conifer forests. Most studies have focused on climatic and environmental stressors and have obviated the potential role of historical forest management as a predisposing factor of decline. Here, we assess if the recent silver fir (Abies alba) decline observed in the Spanish Pyrenees was predisposed by historical logging and incited by warming-induced drought stress. We analysed a dataset of environmental, structural, and historical variables at the tree and stand level including 32 sites with contrasting degrees of defoliation distributed over 5600 km². We followed a dendroecological approach to reconstruct historical logging and to infer the effects of warming-induced drought stress on growth. The silver fir decline was more severe and widespread in western low-elevation mixed forests dominated by trees of small size and slow growth. These sites were subject to higher water deficits than eastern sites, where late-summer rainfall as the key climatic variable controlling silver fir growth was higher. Declining sites showed more frequent growth releases induced by historical logging than non-declining sites. Historical logging and warming-induced drought acted as long-term predisposing and short-term inciting factors of silver fir decline in the Pyrenees, respectively. We suggest that biomass increases caused by past intense logging affected the vulnerability of silver fir against late-summer water deficit. Future research in declining temperate conifer forests should consider the interacting role of predisposing historical management and inducing climatic stressors such as droughts.  相似文献   

茶多酚和铜对可变电荷土壤钙镁释放的影响   总被引：1，自引：0，他引：1  

朱小芳  唐昊冶  钱薇  龚华  徐仁扣  俞元春  王如海  王平 《土壤》2019,51(3):536-540

通过批平衡试验,研究茶多酚、铜和体系pH对可变电荷土壤释放钙镁离子的影响。研究发现,铜离子初始浓度为2.0mmol/L,最终体系pH为5.0时,随着茶多酚添加量的增加,可变电荷土壤表面的负电荷增加,土壤表面释放的钙镁离子量减少。茶多酚初始添加量为20 g/kg,最终体系pH为5.0时,随着铜离子初始浓度的升高,可变电荷土壤对铜离子的吸附量增加,铜离子通过与钙镁离子发生离子交换,形成对吸附位点的竞争,从而增加钙镁离子的释放。茶多酚初始添加量为20 g/kg,铜离子浓度为2.0 mmol/L,随着pH的升高,可变电荷土壤钙镁离子释放量下降。在相同pH条件下,茶多酚可以通过自身的吸附增加可变电荷土壤表面负电荷,减少可变电荷土壤钙镁离子的释放量。研究结果可为茶园土壤酸化和污染控制提供参考。  相似文献   

利用长毛钝绥螨控制冬瓜上二斑叶螨研究   总被引：5，自引：0，他引：5  

候爱平  张艳璇 《昆虫天敌》1996,18(1):29-34

冬瓜是南方主要蔬菜品种之一，遭受二斑叶螨Ｔｅｔｒａｎｙｃｎｕｓ ｕｒｔｉｃａｅ（Ｋｏｃｈ）严重危害。作者在冬瓜生长五叶期每株释放长毛钝绥螨Ａｍｂｌｙｓｅｉｕｓ ｌｏｎｇｉｓｐｉｎｏｓｕｓ３０只，１周后二斑叶螨下降９１．５％。并能控制叶螨的增殖直至收获期。室内对长毛钝绥螨与二斑叶螨间的相互关系进行探讨。  相似文献