The Influence Of Simulating Forest Canopy Damage On Soil ABA Pool In Evergreen Broadleaved Forest Of Nanling Mountains

Abscisic acid (ABA) is a kind of plant hormones synthesized by plant and play an important role in plant growth regulation. endogenous abscisic acid synthesized by Plant can spread into the forest community and formed the exogenous abscisic acid by litter, throughfall, stemflow and root secretion, and discomposed or lossed through the microbial, illumination, surface runoff and finially reach a dynamic balance in community soil. A massive ice and snow storm occurred in early 2008 in south China and caused extensive damage to forests. Exogenous abscisic acid (ABA) is an important allelochemical and it can accumulate in the soil through successional processes and have an important influence on forest succession. In present, extremely climate event become more frequently and can bring serious damage to forest and change its composition in abroad area. But the dynamic of ABA in a damaged forest community and its effect on forest composition is not be clearly researched. We expect this research can consummate the theory about forest community dynamic and provide a new opinion on the technology of damaged forest quickly restoration. In this paper, we selected evengreen broadleaf forest slightly influenced by the ice storm in Xiaokeng, Nanling Mountain and conducted a canopy trimming experiment to simulated the damage of ice storm on forest canopy. Additional, a removing or adding experiment was conducted to research the influence of fresh litter on foreset recovery and community dynamics. The ABA content in samples were analysed using a enzyme-linked immunoassay (ELISA).the ABA input by litters, through fall and trunkflow stream and ABA output by surface runoff in different treatment plot were calculated, the ABA concentration if soils of different treatment plots and the ABA decomposition characteristics were ayalysed. The influence of canopy damage on soil ABA pool were revealed by comparing the ABA intput and output amount in different treatment plot. This paper obtained the main conclusions as follows:(1)The canopy damaged forest producted less litters than normal forest in April and July, but the production was same with normal forest in January and October.the annual inputment in canopy damaged forest was about 75% contrast with normal forest. The ABA content in litters from damaged forest was lower than litters from normal fores. Canoly damage decresed about 56% of the ABA input by litters contrast with normal forest. The remove or addition of trimiing detritus has no significantly influence on forest litter production and ABA content in litters.(2)The thoughfall in canopy damaged forest was higher than normal forest, but not obviously. The steamflow and sureface flow in canopy trimed plot was were lower than notrimed plot. The ABA concentration in thoughfall, steamflow and sureface flow in canopy trimed plot was lower in May-August but higher in September-November than in notrimed plot. The ABA inputment by thoughfall and steamflow and the outputment by surefaceflow were mainly depends on the rainfall.(3) The ABA inputment by litters, thoughfall and trunkflow contributed about 30%,48% and 22% of all these three inputment pathway in normal plot, and 23%, 61% and 16% in trimed plot respectively. Leaching was one of the important pathway of ABA into soil.(4) The ABA content in the soil of sample plot was about 100ng·g-1 dry siol, according with the successional stage of this forest. The sequence of ABA content in different months is October>January>April>July. There were no significant difference between different treatment plot in all sampled month.(5) The concentration of ABA in soil solution was positively correlation with soil total nitrogen, its inner link mechanism is unclear. Under conditions of labary culture, soil microorganisms can break down some soil ABA (16.1～45.8%) rapidly in few days and after that ABA show the slow linear decomposition, decomposition rate of 0.24%·d-1.The high concentration ABA in soil solution has a more quickly decomposition rate in prophase incubation and a more slowly decomposition rate than low concentration ABA, indicating that soil microorganisms not only accelerate the ABA decomposition and also avoid dramatic loss of ABA in soil.