Studies On The Relations Among Litter,Soil Nutrients And Fine Root Biomass Of Casuaria Equisetiflia Plantation As Windbreak On The Coast Of North Hainan Island

In order to study the relations among litter,soil nutrients and fine roots biomass of Casuaria equisetiflia plantation as windbreak on the coast of north Hainan Island, we used the paired-plot design with control and treatment sites at Gui Linyang, Haikou. We respectively conducted experiments on litter,nutrients return from litter,standing crops of litter,litter decomposition,nutrients of soil and fine roots biomass. In each plot , we randomly fixed up 3 litter traps to collect litterfall, and took some leaves to make some chemical analysis (mainly to determine the content of nitrogen,phosphorus and kalium ) and to calculate the nutrients return from litter. we laid 3 1.0m×1.0m sub-plots in each plot and collected all the litter in it directly to determine its standing crops. The litterbags were retrieved on the 90th,180th,270th,360th and 547th day in the experiment of litter decomposition for calculation of the mass remaining percentage of litter and the nutrients releasing percentage (mainly about the remaining percentage of nitrogen, phosphorus and kalium). In each plot, we sampled soil at random and analyzed the content of nitrogen and phosphorus. At the same time, we sampled fine roots at random by soil coring and chose the fine roots (d<2mm) to calculate biomass. The main results are as follows:1. The annual litter in the sites of control and treatment is 5.9505 t·ha-1 and 6.0162 t·ha-1 respectively. According to the statistic analysis, there is no significant difference between the two sites.2. It seems that the temporal patterns of litterfall are similar in the two sties. In litter, the leaf litter takes up the largest percentage and their monthly dynamics is similar with the total litter. The miscellaneous litter takes the second place. And bark+branches litter takes the least percentage.3. It seems that there is a same monthly pattern of N,P and K return from the litter in the two sites respectively. The order of quantity about the nutrients return from the leaves is: N>K>P.4. The standing crops of litter in treatment site is 15.90t·ha-1 and that in control site is 14.49t·ha-1, but according to the statistic analysis there is no significant difference between the two sites. And in the two sites'standing crops of litter, leaf litter takes up the largest percentage.5. The litter decomposition rate in control site is larger than that in treatment site. During the process of decomposition, there is no net accumulation on the N,P and K in the two sites, but the percentages of release of the three elements in control site is larger than that in treatment site.6. If there is no fresh litter in the treatment site in a short time, the soil also makes some progress, so as to make the decomposition and accumulation on nutrients, but it is less significant than that in the control site. In treatment site, nitrogen content in soil and phosphorus returns from leaf litter are significantly correlated, and the soil phosphorus content and the litter mass are significantly correlated.7. The seasonal dynamics of fine roots biomass have a"single apex". There is a significant correlation between the fine roots biomass and the soil phosphorus content in control site.