Study On The Plant Diversity Of Patch Community In A Marsh In Sanjiang Plain

Habitat fragmentation may decrease plant species diversity directly or indirectly by losing habitat which support the plants on it, reducing core area of habitat or reproductive isolation. Habitat fragmentation is a major characteristic of the landscape in the Sanjiang Plain in northeastern China. Based on Quick Bird satellite image data, the present study examined small-scale herbaceous community patches in the marsh of the Sanjiang Plain and measured patch characteristics such as the area, perimeter and shape. The coenological characteristics of the patches were investigated using quadrat (1m x 1m) methord, and the vascular plant species were recorded using transect method. Five indices were selected to describe plant diversity of the community patches: Species number (S), richness index (R), the Simpson index (D), the Shannon-Wiener index (H′), and the Pielou index (Jsw). Shape index (SI) was used to describe the shape of patches. Based on the area sizes, the 37 vegetation patches were classified into three categories (large, medium, and small) based on the Cluster Analysis.The results showed that S correlated with patches'areas(r= 0.58,p= 0.000) and perimeters(r= 0.66,p= 0.000); R correlated with perimeters(r= 0.37,p= 0.026) and SI (r= 0.37,p= 0.025); D correlated with patches'areas(r= 0.37,p= 0.023); H′correlated with patches'areas(r= 0.49,p= 0.002) and perimeters(r=0.42,p= 0.011). The relationship between the number of species and the area sampled could be described by the model of S = cA^z in Island biogeography.A total of 219 plant species was recorded, which represents 12.2% of the vascular flora in Heilongjiang province. The average area of the patches was 8738±1045 m², and the average number of species per patch was 59±3. A significant difference in the number of species per patch was found between large and small patches (p= 0.000)and between medium and small patches(p= 0.001), the three hierarchy patches show signigicant difference among each other(F_2,34= 13.169, p = 0.000). Some weeds from the regional farmlands were also found in every patch. The plant species in small paches formed in different year showed significant difference among each other(F_3,23 = 3.294, p= 0.041), longer the patches formed less the plant species it contained. Some plant species in the big hierarchy patches did not grow in the small paches,eg. Achillea alpina, Saussurea salicifolias, Platanthera.hologlottis,...