Sử dụng Microcosms, Mesocosms, và trường Các thí nghiệm Đánh giá phản hồi hệ sinh thái để các chất gây ô nhiễm và căng thẳng khác Khi có các yếu tố được lựa chọn để điều tra, nó không phải là vì chúng ta dự đoán rằng các quy luật tự nhiên có thể được thể hiện với bất kỳ đơn giản đặc biệt trong điều khoản của các biến này, nhưng bởi vì họ là các biến có thể được kiểm soát hoặc đo một cách dễ dàng so sánh. (Fisher 1960). | 32 The Use of Microcosms Mesocosms and Field Experiments to Assess Ecosystem Responses to Contaminants and Other Stressors When factors are chosen for investigation it is not because we anticipate that laws of nature can be expressed with any particular simplicity in terms of these variables but because they are variables that can be controlled or measured with comparative ease. Fisher 1960 INTRODUCTION Results of field surveys and other descriptive approaches have provided a solid foundation by which to evaluate the effects of contaminants on ecosystem processes. These studies have shown that certain functional characteristics of ecosystems especially productivity nutrient flux and decomposition are quite sensitive to anthropogenic disturbance. However as we noted in the previous chapter descriptive studies are limited because of the inability to demonstrate cause-and-effect relationships and because of difficulties identifying underlying mechanisms responsible for changes in these ecosystem processes. Complex interactions and indirect effects of chemicals are likely to be the rule rather than the exception in many ecosystems. In addition community inertia defined as the tendency for communities to persist under unfavorable conditions following disturbance Milchunas and Lauenroth 1995 complicates evaluation of ecosystem responses to perturbation. Isolating causal mechanisms is particularly important in ecosystem studies because these processes are often complex and controlled by an assortment of direct and indirect effects. For example litter decomposition in aquatic and terrestrial ecosystems is regulated by microbial processes and activity of invertebrates. Because effects of contaminants on decomposition rate are dependent on the relative sensitivity of microbial and macroinvertebrate communities experimental approaches that isolate these different mechanisms are necessary to predict effects. This is an ideal application of microcosm and mesocosm .
