海南三亚河红树凋落物产量与季节变化研究

Production and seasonal change pattern of litter fall of Rhiz ophora apiculata in Sanya River mangroves,Hainan Island

在海南三亚河红树 (Rhizophora apiculata)纯林区设置 4个 1 m2 凋落物收集网于 1 999年全年逐旬收集 ,4个网的平均年凋落物总产量为 1 388.2 4 g/ (m2· a) ,其中叶 79.9% ,枝 8.8% ,花 6.4% ,果 4.9%。与国内外有关资料对比 ,三亚河红树纯林凋落物产量是很高的 ,主要与树较高、低纬度、河流型和林带窄有关。凋落物总产量有多峰值的季节变化 ,峰月依次为 1 0～ 1 1月份、4月份和 8月份 ,谷月依次为 1 2月份、5月份和 9月份。叶的产量的峰谷变化与总产量相一致。枝的产量 77%的网次为 0 ,仅 2、8、9、1 0、1 1月份形成 5个峰值 ,其中后两个最大的峰值对总产量峰值的贡献达占 31 .7%和 31 .2 %。花的产量在 3～ 5月份略显平坦的峰值 ,8～ 1 2月份维持较低的产量。果的产量在 6～ 7月份有一个较宽的峰 ,1 0和 1 1月份有两个窄峰 ,1 2月份至来年 4月份基本上没有产量。花和果的凋落物产量变化明显与植物物候期有关。取 1 999年逐旬平均气温、降水量和平均风速资料与相应的凋落物产量进行相关分析显示 ,平均气温宏观控制叶凋落物产量和凋落物总产量 ,枝凋落物产量主要受平均风速影响。估算整个三亚河 1 4 hm2 红树林区可年产凋落物1 9 4t。

Sanya River mangroves (18°15 3′N,109°30 8′E), distributing along the sh ore of the estuary or lagoon of downstream Sanya River which passes through Sany a City of Hainan Island in China and inpours into the top of Sanya Bay, are one of the southernmost mangroves in China. Among of them a thermophilic eurytopic species Rhizophora apiculata can form a pure species forest, which is the mo st typical tropical mangrove community in China. The litter fall of Rhizophora apiculata forest of Sanya River mangroves was collected with 4 trap nets every 10 days for the whole year of 1999. The mean an nual litter production for the 4 trap nets was 1388 24g/(m 2·a), with litte r productions of leaf, branch, flower and fruit up to 79 9%, 8 8%, 6 4% and 4 9% respectively. This total production was quite high in comparison with the r elated external research data and the internal data on 5 other sites. This high production was mainly related to the geographic location of low latitude, the ri verine community type and the community structure feature of tall tree and narro w mangrove belt . Sanya City in southern Hainan Island has a tropical marine mon soon climate, with obvious wet and dry seasons. The annual temperature and rainf all in 1999 were a little higher than usual, but there was no typhoon influence, so this high litter production could not be induced by meteorological factors. The total litter production had a seasonal change pattern of multiple peak value s, with production peaks in months of Oct.~Nov. (taking up 26 25% of the annual production), April, and Aug., and production valleys in months of Dec.~Feb. (ta king up 10 56% of the annual production), May, and Sep. in the order from high to low. The leaf litter production, as the main body of the total, had the same peak valley change pattern with the total litter production. The branch litter production was of sparse pulse pattern, with zero production in 77% of the total nets and 5 production peaks respectively in Feb., Aug., Sep., Oct., and Nov., t he latter two peaks made contributions of 31.7% and 31 2% respectively to the t otal production. The flower litter production had a flat peak in March^May and a low level in Aug.~Dec. The fruit litter production had a wide peak in June^July and two narrow peaks in Oct. and Nov. There was basically no production during Dec.~April.Taking the values of the mean air temperature, rainfall and mean wind speed of Sanya City every 10 days for the whole year of 1999 to conduct a corre lation analysis between the litter fall productions and the above meteorological factors. The results showed no strong relationship between any litter fall prod uction and any meteorological factor in general. Only the total litter productio n and the leaf litter production had relationships to the mean air temperature, with quite high correlation coefficients and a significance level of α=0.05 , showing that the total and the leaf litter productions were generally affected by mean air temperature. The relationship between the branch litter production and the mean wind speed had a little high correlation coefficient, and they had the same main peaks, which meant that mean wind speed was a main factor for bran ch litter production. The litter productions of flower and fruit were related ob viously to plant phonological phase. The complicated seasonal change patterns of mangrove litter fall production are affected by many factors, of which temperat ure, wind speed and phonological phase are main. Litter fall of mangroves is an important component of their primary production a nd a key link of mangrove matter and energy flow. It was estimated that the tota l annual litter fall production of 14 hm 2 mangroves over the whole Sanya Rive r was up to 194t. Little accumulated litter fall on the mangrove flat and low or ganic matter contents of mangrove soil over Sanya River mangroves showed that mo st of the mangrove litter fall had been transported into Sanya Bay and become im portant matter and energy sources of organic detritus food c