Abstract:

Generally wetland functions can be divided into three types: hydrologic, habitat and biogeochemical functions. Each of the three functions includes several sub-functions, each of which is manifested by a measurable and quantitative variable. A combination of all the variables forms the functional assessment index system of wetlands. The intrinsic fuzzy features of wetland functions make it possible for fuzzy mathematics method to be widely used in functional assessment of wetlands. The essence of application of fuzzy set theory to functional assessment of wetlands is to identify the membership degrees of the target wetlands to give fuzzy sets. The main principle of a Dual-Grade Fuzzy Pattern Recognition Model is to quantitatively assess the functional status of a target wetland through calculation of its membership degree to idealistic and worst functional circumstances. For any wetland to be assessed, the possible maximum values of its variables in undisturbed pristine situation are adopted as the standards of idealistic circumstance, and the possible minimum values of its variables in human_disturbed situation are adopted as the standards of worst circumstance. The established model has been applied to assessment of wetland functions in Honghe National Nature Reserve in Sanjiang Plain, Heilongjiang Province in the years of 1980, 1988 and 2002. The calculation results showed that the membership degrees of this wetland to idealistic circumstance was 0.974 3 in 1980, 0.857 3 in 1988 and (0.703 0) in 2002,suggesting that wetland functions in Honghe have been evidently decreasing since 1980.

Key words: functional assessment of wetlands, Dual-Grade Fuzzy Pattern Recognition Model, Honghe National Nature Reserve