The disturbance effect of the surroundings on the water environmental health of urban wetland park: A case study on Xixi Wetland Park, China

Abstract

Wetland is the highly disturbed area among the types of landscape. The urban wetland is the ecosystem prone to be disturbed because of large population and human activities. These disturbances were coming from not only the inner but also the surrounding areas of wetland. The relationships between water quality and disturbance(land use change)obtained in the previous studies are usually analyzed in terms of the inner of wetland landscape. Obviously, fewer studies have focused on the fact that the spatially varying impact is caused by some factors outside the study area and the water quality of the inner of the study area in the previous studies, and that higher land use intensity and population density around the wetland park may change the ecological process. As the most vulnerable ecological system,water environment will be impacted first. The spatial diversity of disturbance from the surroundings of the wetland park will be identified, and the relationship between the disturbance and water environment can be quantitatively analyzed.In order to capture disturbance from land use changes, we used SPOT5 images of the study area in the years of 2003 and 2009. The NDVI index was used to analyze the vegetation disturbance and its dynamics. In our study, differences of NDVI between two periods at the same location were considered as disturbances, in which they refer to detectable change in land use and land cover. Then to analyze the effect of disturbance from outside the wetland Park, we measured the proportion of disturbance adjacency(pdd) of landscape using a moving window algorithm to quantify the spatial distribution of disturbance. We also used water quality data to developed water environmental health index. And the purpose of this paper was to find how human disturbance surrounding the wetland affects the water quality and its health. The results show that(1) about 37.7% of the surrounding area was disturbed. The disturbing regions were mainly located in the northern surrounding and less in the eastern surrounding of the wetland;(2) about 64% of park area was influenced by disturbance around the wetland, the influence of interference decreased sharply from the park edge to the center;(3) water environmental health index had obvious difference under different influence degrees. TN, TP and Chla concentrations were the highest and water environmental health index was the lowest in strongly- affected areas. TN, TP and Chla concentrations were the lowest and water environmental health index was the highest in non- affected and weakly affected areas. This study could help us get a better understanding of the influence of the planning and building around the wetland park on the sustainability of the wetland park.