The Assessment Of Wetland Ecosystem Health By Means Of Ldi And Wrap

Wetland is one of the most important habitats for the living creatures on earth, which is also one of the eco-landscapes with richest biodiversity. Wetland offers people not only a variety of resources but also huge environmental functions and benefits. However, in recent years, from microscopic to macroscopic, from genes to populations and communities, from organization structures to function processes, wetland ecosystems have been suffering from the unprecedented impacts. The development of human society has been threatened due to the reduction in the number and area of wetlands, the decreasing biodiversity, the deterioration of water quality, and the eutrophication in wetlands. Wetland ecosystem health (WEH) has become on of the hotspots in the research of wetlands.Based on the latest progress in the field of WEH at home and abroad, we took the Baiyangdian wetland ecosystem for example to evaluate the health condition of the typical wetlands located in the Huang-Huai-Hai region quantitatively, by means of both LDI (landscape development intensity index) and WRAP (wetland rapid assessment procedure).This thesis firstly reviewed the status quo and development trends of WEH research with focus on the WEH assessment methodologies and existing corresponding shortcomings. We held that the US "three-tier framework" was a comparatively complete system of WEH assessment. A more detailed theoretical and empirical analysis about LDI and the WRAP was presented. After that, these two methods were used to assess the health condition of Baiyangdian wetland, a marshland lying on the central Hebei province, china. The validity and robustness of the methods were evaluated. The overall and partial health condition of Baiyangdian was showed.The main outputs are summarized as follows:1. The LDI index and WRAP belongs to Level 1 and Level 2 respectively in the "three-tier framework". Both of the two methods have sound theoretical foundations and mature applications. LDI provides information on the condition of wetlands in landscape-scale relying on remote-sensing imagery and Geographic Information System (GIS). As a quantitatively measure of the intensity of human use of landscape, LDI can be used to evaluate a large area or a large number of wetlands with minimal data acquisition. The shortcoming of the method lies in that the accuracy is relatively low in some single and small wetlands.The WRAP gives a general idea of wetland condition and probable stressors through on-the-ground surveys in local or regional scale. The advantage of the method lies in that it provides sound, quantitatively information on the status of the wetland resource with a relatively small investment of time and effort, and the accuracy is moderate.2. The results of the LDI indicated that a 100m buffer was adequate to capture surrounding land use effects. The significant difference in LDI scores among the a priori classes suggested that LDI was a sensitive assessment tool which could distinguish different levels of anthropogenic disturbances. The strong correlation was found between the LDI and WRAP (spearman'r=-0.821, p=0.023), which illustrated that LDI (Level 1) could be validated by WRAP (Level 2). The results of LDI and WRAP were also highly correlated with the physico-chemical parameters of soil samples, which furtherly demonstrated the validity of these two methods. These results provided supportive evidence of the usefulness of the LDI and WRAP as Level 1 and Level 2 procedures for the identification of the Baiyangdian wetland health condition.3. The LDI score of the entire Baiyangdian wetlands was 3.97, which was closed to the threshold of urban wetland. Overall, Baiyangdian wetland has deteriorated seriously, and it's hard to find a completely natural wetland area as a result of the full-scale anthropogenic disturbances. Besides, the variously scores of the LDI and WRAP in the subarea scale reflected the spatial variation of wetland health condition in Baiyangdian.