Preliminary Study On Effects Of Extreme Events On Litter Production In An Evergreen Broad-leaved Forest In Tiantong, Zhejiang Province

Litterfall is a very important component of the forest ecosystem. The input of litterfall can maintain the soil fertility, improve the soil physical and chemical properties, and conserve soil moisture. Recently years, the frequency of the extreme weather events has been increased, litter production fluctuates due to the extreme weather. The fluctuations of the litter production will also affect on the nutrient cycling of the forest ecosystem. Therefore, it is important to study the dynamics and the spatial distribution of litterfall after these distribution. To research litterfall production, dynamics, spatial distributions, and nutrient cycle in forest ecosystem, we set up 187 litterfall traps in an evergreen broad-leaved forest at Tiantong, Zhejiang, classify the habitat into 7 types, and collect litterfall semimonthly from January 2012 to December 2014. We analyze the response of litterfall after extreme weathers under different terrain conditions and the main conclusions are as follows:1) The total litter production has a normal level of volatility during the 3 years. Leaf litter is the main component of the total litter, followed by branch, the amount of reproductive organs and bark are the smallest proportion of total litter. The total litter, leaf litter, branch, reproductive organs and bark are insensitive to typhoon and drought during the investigation (p>0.05). Although the disturbances don’t have significant effect on annual total litter production, they do have a noticeable impact on leaf litter and branch right after the disturbances. The amount of leaf litter and branch are increased significantly within half month after the occurrence of typhoon and one month after the occurrence of drought. And the increase of branch is higher than leaf litter. Reproductive organs and bark are insensitive to the typhoon and drought.2) Leaf litter and branch present significant differences in 7 habitats right after the typhoon and half month after drought. Litter production is affected immediately after a typhoon, the impact will delay half month after drought. After the typhoon, leaf litter increases most in the disturbed habitat, which may due to the growth of tall deciduous trees in this region. The amount of branch increases most in the low ridge. The increase of litter production in the low altitude regions is higher than the high altitude regions. Litter production is more likely to be affected in the low altitude regions. The similar tendency can be seen after the drought, the amount of leaf litter and branch increase more in the low altitude than in the high altitude after the drought.3) We choose 21 dominant species in the study region to analyze the response after the typhoon and the drought, most species have no significant difference on leaf litter after disturbances because of the compensative effect. The typhoon and the drought have different influences on species. The amount of dominate species leaf litter is less sensitive to the influence of the typhoon. Meanwhile, evergreen species are more susceptible to the drought within a short time, deciduous species are affected by the drought within a longer time. The vegetation is more adaptive to the frequent typhoon disturbance than the drought. According to the analysis, the dominant species can be classified into five categories, insensitive species, typhoon sensitive species, drought sensitive species, response delayed species and abnormal species.4) In the analysis of the dominant species leaf litter with habitats, Acer pubinerve leaf litter is the only part which is affected by the typhoon in different habitats, Cinnamomum subavenium and other 4 species leaf litter are affected by the drought in different habitats. Dominate species leaf litter in high altitude region and disturbed habitat is easier to be influenced. For other dominant species, the effects of the typhoon and the drought are not significant in different habitats.Generally, there was no significant effect on the litter amount after the typhoon and the drought. Typhoon has transient effect on litter production, while drought has long-term effects on litter production. The amount of litter in the low altitude area is more vulnerable to the typhoon and the drought. For dominant species, extreme weathers has changed the distribution of some species leaf litter.