| Wetlands are one of the most vital ecosystems on Earth, which play a crucial role in maintenance of biodiversity and construction of human ecological environment.Strengthening the research of wetland landscape pattern change, we can comprehend the spatiotemporal evolution rule of wetland landscape pattern, and it has great significance on the maintenance of biodiversity of wetland and ecological protection and the promotion of socio-economic development.Recently, under the influence of natural and economic factors, the ecosystem of Nanji wetland in Poyang Lake are confronted with serious threats and damage, also it has great influences on weakening the wetland functions. Therefore, in this paper,Nanji wetland national nature reserve were selected as the study area, the 20 scenes of Landsat images from 1973 to 2010 and 1 scene GF-1 image in 2013 were collected as the data source, we utilized decision tree classification and object-oriented classification method to extract their wetland information. Finally, ArcGIS, and ENVI and Fragstas4.2 software were used to analysis the dynamic change of landscape pattern. Main results of this paper are shown as follow:(1)Construction of the Nanji wetland classification decision tree model and object-oriented classification rules. In this study, by establishing the Nanji Wetland decision tree classification model, and series of Landsat images were collected to quickly extract wetlands information. Meantime we applied the object-oriented classification method to classify the GF-1 image, and the result indicated higher classification accuracy of 94.3275% and kappa coefficient is more than 0.9324.(2)According to the interpretation results of GF-1 image in winter 2013, the landscape pattern characteristics of different wetland types were analyzed, the results displayed that water, mudflats, grassland are the major wetland types existing in Nanji wetland; the degree of fragmentation of water is the most severity, and the landscape shape of mudflat is the most complex; the degree of fragmentation and landscape diversity in the southwest of the Nanji wetland is higher than the northeast region.(3)Utilization the interpretation results of 5 similar water level images in 1973,1984, 1999, 2003 and 2010, through analyzing the dynamic degree of landscape,transfer matrix of landscape, and spatiotemporal variation of landscape in Nanji wetland separately in 4 different stages(1973-1984, 1984-1999, 1999-2003,2003-2010), The changes rules of wetland types in different status were obtained. The results showed that Nanji wetland have undergone fall-fall-rise-fall four different stages since 37 years. From 2003 to 2010, the transformation of the wetland type in Nanji wetland is more distinct and more extensive range.(4)Analyzing the spatiotemporal changes of wetland landscape pattern fromthe class level and landscape level respectively in the past 37 years. The results indicated that the wetland landscape in Nanji wetland tended to be more fragmented and smaller, complicated landscape shape, and the declining diversity; the region with higher degree of fragmentation, landscape shape and diversity index had a tendency to focus on the southwest area.(5)Via calculation and analysis of the landscape pattern of Nanji wetland in different water level. The results displayed the correlativity between water level and landscape fragmentation, landscape diversity and landscape evenness index are negatively correlated; inversely, the water level and landscape contagion index showed a significant positive correlation. |
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