tailieunhanh - ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 35

Căng thẳng trong khí quyển toàn cầu tạo ra phân phối rộng rãi nhiễu loạn vật lý và hóa học tác động đến cấu trúc và chức năng của hệ sinh thái. Ngoài ra để phân phối phổ biến của họ và các nguồn khuếch tán, căng thẳng trong khí quyển toàn cầu đặc biệt là vấn đề bởi vì họ không bị giới hạn bởi ranh giới địa chính trị. Trong chương 26, chúng tôi mô tả những tác động của căng thẳng khí quyển trên toàn cầu phong phú, đa dạng loài, thành phần cộng đồng, và các. | 35 Effects of Global Atmospheric Stressors on Ecosystem Processes INTRODUCTION Global atmospheric stressors create widely distributed physical and chemical perturbations that impact the structure and function of ecosystems. In addition to their ubiquitous distribution and diffuse sources global atmospheric stressors are especially problematic because they are not restricted by geopolitical boundaries. In Chapter 26 we described the effects of global atmospheric stressors on abundance species diversity community composition and other structural characteristics. Here we will focus on descriptive and experimental studies that assess effects of increased CO2 N deposition acidification and ultraviolet radiation UVR on the function of aquatic and terrestrial ecosystems. NITROGEN DEPOSITION AND ACIDIFICATION In Chapter 30 we described biogeochemical cycles and the important processes that control movement of elements in aquatic and terrestrial ecosystems. Significant increases in the global reservoirs of C N and S as a result of combustion of fossil fuels and agricultural land use changes disrupt these natural cycles and have contributed to a variety of local and global environmental concerns. Global emissions of biologically reactive N compounds . NH3 NH4 HNO3 and NO3 have increased from about 15 teragrams Tg in 1860 to more than 165 Tg in 2000 Galloway et al. 2003 . Although effects of increased N deposition have not attracted the same attention from scientists and the public as other global atmospheric stressors such as chlorofluorocarbons CFCs and CO2 N poses serious threats to ecosystem processes. Potential negative effects of excess N on forest ecosystems were first described by Nihlgard 1985 . Biologically reactive N compounds that accumulate in the atmosphere are rapidly deposited on the earth s surface where they can affect net primary productivity NPP Aber et al. 1995 disrupt N dynamics in soils Gundersen et al. 1998 and contribute to eutrophication