tailieunhanh - ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 25

TẦM QUAN TRỌNG CỦA xáo trộn trong cơ cấu CỘNG ĐỒNG Trong chương này, chúng tôi sẽ so sánh những cách mà các cộng đồng đáp ứng với rối loạn tự nhiên và con người. Chúng tôi đề nghị rằng nhiều trong những đặc điểm xác định sức đề kháng và khả năng phục hồi của cộng đồng xáo trộn tự nhiên cũng có thể ảnh hưởng đến phản ứng với căng thẳng hóa chất. Theo mục đích của cuộc thảo luận này, rối loạn được định nghĩa là bất kỳ sự kiện rời rạc mà phá vỡ hệ sinh thái,. | 25 Disturbance Ecology and the Responses of Communities to Contaminants It is one of those refreshing simplifications that natural systems despite their diversity respond to stress in very similar ways. Rapport et al. 1998 THE IMPORTANCE OF DISTURBANCE IN STRUCTURING COMMUNITIES In this chapter we will compare the ways in which communities respond to natural and anthropogenic disturbances. We suggest that many of the characteristics that determine resistance and resilience of communities to natural disturbance may also influence responses to chemical stressors. For the purposes of this discussion disturbance is defined as any relatively discrete event that disrupts ecosystem community or population structure and changes resources substrate availability or the physical environment White and Pickett 1985 . Key features that determine the impact of disturbance on communities are the magnitude . how far the disturbance is outside the range of natural variability frequency and duration. Some ecologists define disturbance as any event that results in the removal of organisms and creates space. Indeed some ecology textbooks . Begon et al. 1990 combine discussion of disturbance and predation in the same chapter because they ultimately have similar effects on communities the removal of organisms from a community. The impact of a predator on a competitively superior species will have a qualitatively similar influence on community structure as the creation of space by physical disturbance. However most community ecologists limit the definition of disturbance to include only events that are outside the range of natural variability. In other words the predictability or novelty of a disturbance event greatly influences community responses and recovery times. Predictability of disturbance is largely influenced by the frequency of occurrence but also varies among ecosystems and disturbance types Table . Johnston and Keough 2005 conducted one of the few field .