Study on Effects of Urbanization on Vegetation Landscape Pattern in Chengdu City

In order to understand the changes of vegetation landscape pattern in Chengdu during the urbanization process, the main characteristics and changes of vegetation landscape pattern in Chengdu from 2002 to 2017 were analyzed by selecting the existing mature landscape pattern index from four aspects: the basic characteristics of vegetation landscape elements, the diversity of landscape elements, the basic characteristics of landscape element patches and the shape characteristics of landscapes. The main results were as follows: (1) Compared with 2002, two vegetation types were missing in 2017, evergreen broad-leaved shrubs and shrub grass on low hills, which were mainly the results of the combination of natural succession and human activities. (2) The basic characteristics of the vegetation landscape elements in Chengdu showed that the total area of vegetation landscape in Chengdu in 2002 was 13757.59 km², accounting for 95.97% of the total area of Chengdu; in 2017, the total vegetation landscape of Chengdu was 11, 147.32 km², accounting for 83.34% of the total area of Chengdu. (3) The results of the vegetation landscape element diversity analysis showed that in 2002 and 2017, the richness index (1.364 and 1.172), the evenness index (0.653 and 0.742), and the diversity index (1.723 and 1.843) of vegetation landscape in Chengdu were lower, and the dominance index (4.362 and 4.328) was higher. (4) The results of the basic feature of landscape elements patches analysis showed that the overall landscape fragmentation degree of Chengdu is lower, but the landscape fragmentation index in 2017 was about five times of that in 2002, indicating that with the development of urbanization, the overall fragmentation degree of the vegetation landscape in Chengdu was increasing. (5) The results of the shape characteristics of landscape elements analysis showed that the shape index of the vegetation landscape elements in Chengdu was more than 1.5, indicating that it deviated from the circle on the whole. The fractal dimension of each landscape element was greater than 1, which indicated that the shape was more complex. In summary, the vegetation landscape pattern in Chengdu was characterized by high fragmentation of artificial landscape, good connectivity of natural landscape, dominant landscape and low diversity. In addition, the interference of urbanization on vegetation was increasingly prominent, and it was necessary to ensure urban ecological safety through the formulation of scientific and reasonable industrial development policies and land use policies.