Responses Of Synchrony Between Leaf-feeding Insects And Host Plants In Subtropical Evergreen Broad-leaved Forests To Climate Change

Synchrony between the leaf-feeding insects and their host plants, which has been formed during the past thousands of years, plays an important role in maintaining stability of the forest ecosystem. Climate change induced by human activities, especially in spring, has become even more violent recently. It has a strong impact on the synchrony between the leaf-feeding insects and their host plants. Diversity of the leaf-feeding insects would be reduced and fitness of the host plants would be declined seriously if the synchrony were interrupted. It has been a hot issue in Ecology to investigate the variation of the synchrony between the leaf-feeding insects and their host plants induced by the climate change.The subtropical evergreen broad-leaved forest in the eastern of China is the main part of the world’s, which has obvious differences in species composition and community structure to the temperate and tropical forest. An investigation on the representative lepidopteron and common species of host plants in Tiantong National Forest Park in Zhejiang Province was carried out to analysis the effects of climate change on subtropical evergreen broad-leaved forest. Field work, sampling investigation, feeding insects, lab analysis and artificial simulation were used in the investigation to observe the phenology, the leaf traits and leaf herbivory during leaf expanding. Also insect community during leaf expansion was also checked periodically. Occurrence dynamics of lepidopteron, effects of temperature and host plants on development and fecundity of lepidopteron were discussed. Synchrony between the leaf-feeding insects and their host plants was discussed. Together with the changing climate factors, effects of climate change on these two aspects were discussed. Simulation experiments were put out to study the effects of climate change on synchrony between the representative lepidopteron and its host plant. The results and conclusions were as following:1. Leaf phenology in subtropical evergreen broad-leaved forest is affected by climate change significantly, among which the accumulated temperature plays the most important role. Plants get an earlier leaf emergency with a higher synchronism in a warmer March, accompanied with a longer leaf expansion. Those with earlier leaf emergency or shorter leaf expansion are more sensitive to climate change than those with later or longer. The common species show 3 kinds of leaf emergency patterns, unimodal, multi-peak and variational. Plants with variational and multi-peak leaf emergency patterns are more sensitive to climate change than those with the unimodal pattern.2. Among the suitable rangement, appropriate rising in temperature would shortern the development period, increase the survival rate and development level, enhance the fecundity. Also, it could affect the synchrony of the egg-laying and egg-hatching of the leaf-feeding insects by an earlier emergency and a higher index of synchrony. Moreover, the feeding behavior of the leaf-feeding insects is affected by the rising temperature both in feeding preference and food consumption. In general, the climate change at the presesent stage provided favourable conditions for the large outbreak of the insects.3. Leaf feeding insects are strongly affected by their host plants. Nutritional properties of leaf present to be positive for the development of insects by fasterning the development rate, shortening the development duration, enchanting the survival rate and fecundity while the defensive properties reduce the fitness of insects by reducing the survival rate and fecundity.4. Leaf herbivory changes with the varying climate during the leaf expansion. It shows positive correlation with the accumulated temperature while negative correlation with the precipitation. The herbivory frequency is more sensitive to the climate change than herbivory rate. Plants expressed differently on development and defensive syndrome during leaf expansion, less-nutrient and defensive, high-nutrient and defensive, and evasive. Leaves of plants with evasive syndrome soffers more sever leaf damage than those the other two kinds of syndromes. Herbivory frequency of plants with evasive and high-nutrient and defensive syndromes is more sensitive to the changing climate than those with less-nutrient and defensive syndrome. However, herbivory rate of all the 3 kinds of plants are insensitive to the changing climate.5. At present, climate change didn’t interput the synchrony between leaf-feeding insects and their host plants, but increase the population of leaf-feeding insects and lead to severe herbivory. Firstly, the three lepidopteran egg-hatching are in accordance with their host plants leaf expansion, and they responsed similarly to the climate change. Secondly, leaf damage varies in differnet years but it remains to be at low level, and occurrence dynamics of leaf-feeding insects are stable in kinds and composition with no obvious difference in diversity, though various in quantity. Herbivory patterns are stable among different years while the diversity is fluctuant. Thirdly, according to the study on influence of climate warming simulated by the OTC to the synchrony between the development of Biston marginata and leaf phenology of Schima superba, the climate changes nowdays haven’t broken down the synchrony of the two, although the Schima superba suffered more sever leaf damage.In conclusion, occurrence of insects and plants are advanced by climate change, but herbivory is stable. It indicates that the synchrony between the leaf-feeding insects and their host plants has not been seriously interrupted by the climate change. Some of the plants suffer a severe leaf damage means that feeding preferences of the insects were deeply affected by climate change. Amplitude in climate change especial the climate change creates more suitable environment for the insects. It brings out a larger population for insects and more severe leaf damage to host plants, and reduce the fitness of host plants grievously.