木榄母树下2种红树植物幼苗生长特征研究

在广西北仑河口珍珠港内进行木榄母树下栽植木榄（Bruguiera gymnorrhiza)和红海榄（Rhizophora stylosa)幼苗试验。选取3棵母树，分别以每棵母树为中心，在东、西、南、北方向上，离母树5．0m距离内按每0．5m栽植2条胚轴。以1月、4月、7月、10月为冬、春、夏、秋季代表月，测定母树下幼苗的实生高、基径、叶数及分枝等生长指标。结果表明：木榄的平均成活率随时间的推移呈下降趋势，栽植1年后的成活率为67．0％，2年后的平均保存率为48．9％，夏季的成活率较春季的高3．7％；红海榄幼苗成活率总的呈下降趋势，造林1年后成活率为58．3％，2年后的保存率为42．0％。木榄母树下3．0m－5．0m和3．5m－4．5m的中离分别为木榄幼苗和红海榄幼苗的适宜生长范围。2种幼苗生长的季节动态均表现为主茎生长高峰期在夏季，基径生长高峰期在秋季。红海榄苗前3年的生长量和生长速度均高于木榄苗，在苗期生物量构成中红海榄分配给叶的份额逐年增加，木榄分配给叶的份额则逐年减少。

Growth Feature of Seedlings of Two Mangroves Under Mother Trees of Bruguiera gymnorrhiza

The seedling growth trial of B gymnorrhiza and Rhizophora stylosa under mother trees of B gymnorrhiza was conducted in Zhenzhu Harbor,Beilun Estuary,Guangxi. Three mother trees were employed. Two hypocotyls were planted every 0 5 m in east, west, south ,north directions within 5 0 m with mother tree as a centre. Height, basal diameter, leaves and branches of seedlings were determined in Jan., Apr., Jul. and Oct. which stood for spring, summer, autumn and winter respectively. The survival rate of seedlings of B. gymnorrhiza was 67 0% one year after planted, and dropped to 48 9% one more year, and was 3 7% higher in summer than in spring. The survival rate of seedlings of Rh stylosa was 58 3% one year after planted, and dropped to 42 0% one more year. The favor growth area was found from 3 0 m to 5 0 m for seedlings of B gymnorrhiza and 3 5 m to 4 5 m for Rh stylosa.The main stem of these two species had fastest growth in summer, and the basal diameter in autumn. The biomass and growth speed of Rh stylosa were higher than B gymnorrhiza in the first three years. The contribution of leaves of Rh stylosa to the whole biomass increased yearly in seedling stage, but decreased in B gymnorrhiza. The survey indicated that natural habitats of mangrove plants were favored to their seedlings.