Effects Of Habitat Fragmentation On Plant And Arthropods Species Diversity In The Thousand-island Lake Region

This dissertation selects the Thousand Island Lake, whose forming process is typically habitat fragmentation, as its object of study. The purpose of this study is to recover the ecological environment and protect animals and plants in order to effectively promote biodiversity after habitat fragmentation in the future, through studying the change of geographical factors, the application of species richness index, diversity index, dominance index and evenness index of the Thousand Island Lake after its habitat fragmentation to analysis the difference of the diversity of plants and arthropods in different geographical environment. The dominant research methods and results are as follows:1. The study area covers the Xiao Jin Shan Forest Farm of the Thousand Island Lake. The study objects are 51 islands selected based on their size, distance and scope using the grid sampling method. They can be divided into 3 categories: 30 small islands which are ≤1hm2, 17 medium-sized islands from 1 ~ 5hm2, 4 large islands which are >5hm2. The sample size was set to 0.08hm2(28.28m×28.28m) in the selected islands to study the species and quantity of plants and arthropods. Based on the result of the study, there are 137 plant species(including subspecies classifications), among which there are 57 tree species of 29 families; 80 shrub species of 34 families. There are 309 arthropod species of 4 classes, 23 orders, and 140 families, which mainly belong to the class insecta. Censuses are used for the small islands below 1hm2. According to the “species-area” theory in island biogeography, the numbers of arthropod and plant species are correlated with the size of the island. The result turns out to be that the numbers of arthropod and plant species are not only correlated with the size of the island, but also with the shape(perimeter) of the island, with correlation coefficients R=0.819,P<0.01;R=0.736,P<0.01. Obvious edge effect of numbers of plants and insects may exist at the edge of these islands, because of the significant positive correlation between the numbers of arthropod and plant species and the perimeter of the island.2. Curve-fitting of the numbers of arthropod and plant species and the size of the island using log function. The result shows: when the size of the island is comparatively small, the numbers of arthropod and plant species increase at an amazing rate, and in proportion to the size of the size of the island; however, the increase rates of the numbers of arthropod and plant species decline in larger islands, and gradually stabilized. The turning point of the growth rate of the number of plant species is around 4 hm2, and of arthropod species is around 2hm2. These turning points could be future reference for the planning and establishing island reserve areas.3. Based on the analysis of the species and quantity of the plants and arthropods in the sample area, the result of the biodiversity index of both large islands and small islands is:(1) We use analysis of variance for a single factor to study the species diversity index on different islands, which comes to a result that this plant-arthropod index varies greatly because of the size difference of those islands. We use LSD method to conduct multiple comparisons and discover that the plant-arthropod species diversity index increases with the size of the island, which means there are more plant-arthropod species on the larger island. This is in keeping with the classic island biogeography.(2) The analysis of the plant-arthropod diversity shows that: the diversity fluctuation of plants is in line with the variation of the sizes of the islands, but not the diversity fluctuation of arthropods. The diversity index of arthropods and plants varies on different islands. On large islands, the diversity index of plants is the highest, and of arthropods is the lowest. On medium-sized islands, the diversity index of arthropods is the highest. The overall predominance level of plants peaks on large islands, and reaches its lowest point on small islands. The predominance level of trees is most obvious, while the predominance level of shrubs on medium-sized island is even more obvious. There are not many differences in the predominance level of arthropods in medium-sized islands and large islands, which shows that, on these islands, the distribution of arthropods becomes stable, and the predominance status is not obvious. From the analysis of evenness index, the overall evenness level of plants is highest on large and medium-sized islands, and the evenness level of trees and shrubs on small islands is higher than on large and medium-sized islands. The evenness index of arthropods is highest on small islands and the evenness level is lowest. Compared with trees, the evenness level of shrubs is higher on all islands, which shows that the shrub species are distributed more evenly on the islands.4. The protection of the plant-arthropod species after the habitat fragmentation of the Thousand Island Lake is rooted in the verification of the habitat scale. The size of a habitat decides a biogeocenose, and different biogeocenoses need different space scale. Therefore, the protection of the plant-arthropod species in the Thousand Island Lake area should decide the size of the reserve area based on the population density and the MVP of the protected species or key species.