林木个体大小差异对群落地上生物量及物种多样性的影响

Effect of size inequality on aboveground biomass and species diversity of plant communities

植物个体大小差异在植物种群中普遍存在,研究其与群落生产力及物种多样性的相关关系对天然次生林的生态抚育具有重要意义。本文在江苏省南京市溧水县林场选取7块有一定代表性的天然次生林样地作为研究对象,对群落中立木高度、立木径级的变异系数与地上生物量、物种多样性指数(Shannon指数)的相关关系进行了研究。结果发现:(1)立木高度的变异系数总体上小于立木胸径的变异系数,但其对群落地上生物量及群落物种多样性的影响总体上高于立木胸径差异性的影响;(2)郁闭度较低的松-阔混交林中林木个体大小的变异系数与群落地上生物量水平呈正相关,而在郁闭度较高的落叶阔叶林及杉-阔混交林中呈负相关;(3)立木个体大小的差异性与群落物种多样性指数均呈正相关,但在郁闭度相对较小的群落(松-阔混交林)中相关性较小。总体上,个体大小差异性的增加有利于增加群落的物种多样性,并对郁闭度较小群落的地上生物量水平有一定的促进作用。

Size inequality is ubiquitous in plant populations. Studying its influence on community productivity and species diversity is of significance for natural secondary forest management. We selected 7 plots of typical subtropical secondary forest communities in the Lishui Forest Farm, Jiangsu Province. We studied the relationship between the coefficients of variation （CV） of tree height and diameter at breast height （DBH） , aboveground biomass and species diversity index （ Shannon index）. The results showed that, （ 1 ） the CV of tree height was less than that of DBH, but its impact on the community biomass and species diversity was generally greater than that of DBH inequality. （2） In the broad-leaved mixed forest （with a low canopy cover） dominated by Pinus massoniana, community biomass was positively correlated with individual size inequality, while a negative correlation was found in the deciduous broad-leaved forest and in the broadleaved mixed forest dominated by Cunninghamia lanceolata （with a higher canopy cover）. （3） Species diversity was positively correlated with size inequality, but the relationship was weak in the community with low canopy cover. In summary, individual size inequality was beneficial for increasing species diversity, and had a positive effect on aboveground biomass of low cover communities.