Intensity And Patterns Of Castanopsis Sclerophylla Leaf Eaten By Insects, At Qiandao Lake, Zhejiang

Plant and herbivores comprise more than 50% of the organisms on Earth. Herbivory on leaves by insect is common in the forest, and plants have consequently developed multiple strategies against insect herbivores. The interactions between plant and herbivores have profound implications for both ecological and evolutionary processes.C.sclerophylla is the dominant species of subtropical evergreen broad-leaved forests in the eastern edge of the trees, is the vanguard species of evergreen broad-leaved species in secondery succession. Qiandao Lake locate in C.sclerophylla cultivation forest, has 1,078 islands above the area of 2500m~2 when water level reached 108 meters. In order to study relationship between insects and plants in islands habitats, a survey was carried out of intensity and patterns of C.sclerophylla leaf eating by insects on several islands in the Qiandao Lake, Zhejiang Province, then found the following conclusions:1. Insect herbivores were very abundant with 85% of leaves and 10% of leaves area eaten. Herbivory can have numerous negative effects on plant fitness by depressing growth, but the damage mostly was not serious On the other way, the leafof C.sclerophylla maintain the diversity of the insect species.2. The intensity of leaf damage depended on the patterns of leaf area and its frequency. Among the several kinds of damage patterns, people should pay special attention to leaf cutting, which doesn't have high rate of leaf damage, but have high intensity of leaf damage. There were 16 kinds of damage patterns, among which edge defoliation were dominant.3. The predation of C.sclerophylla shows an obvious spatial and temporal dynamic trend. The rate and intensity of leaf damage in the top of Laoshan island are both higher than the bottom, which indicates that the diversity of insect is much higher in the upside of this island. On the aspect of predation time, the majority of damage by herbivores occurs on young leaves when the leaves are young and expanding. Daily rates of leaf consumption on young leaves are 20 times higher on mature leaves.4. The concentration of condensed tannin showed substantial intra-specific and inter-specific variation. The concentration of condensed tannin in old leaves is mostly higher than the young leaves.5. The correlation between the area of island and the predation diversity is not notable, which shows that the predation diversity is affected by many different factors, such as the distance between island and mainland or big island,the wing ability of birds as well as the suitability degree of habitat, apart from the areas of island.6. The predation rate and intensity maintain stable seasonally, which do much favor to the growth of C.sclerophylla leaves as well as the diversity of insect species.