不同林分密度对巨桉养分空间分配及积累研究

选择立地条件相似、生长良好的5a生巨桉人工林为研究对象,通过设置556株/hm2和1 667株/hm2两种不同的林分密度,对其主要营养元素含量、分配及生物量分配进行了研究.结果表明:①两种不同林分密度巨桉单株营养元素含量在不同器官的分配规律基本一致,均为树叶＞树干＞大枝或小枝＞果实＞树皮;②从营养元素和有机质在树干的分配来看,两种密度巨桉人工林P、K、Mg和Ca变化趋势相同,基本随着树干高度增加而增加,有机C在556株/hm2样地随着树干高度增加而逐渐增加,而1 667株//hm2样地则是逐渐减小,N在556株/hm2样地为随着树干高度增加而逐渐增加的趋势,1 667株/hm2样地的变化趋势为先增加后降低再增加的趋势;③从两种密度巨桉生物量的分配看,生物量分配为树干＞树皮或大枝＞小枝＞叶＞果实;④两种密度巨桉人工林营养元素积累量均表现一致规律,均为Ca最多,分别为601.78 kg/hm2和1 204.43 kg/hm2,其次为N、K、Mg和P积累最低.

A Study of the Distribution and Accumulation of Major Nutrient Elements in Different Densities of Eucalyptus grandis

This study was conducted to investigate the distribution and accumulation of major elements of 5-year-old Eucalyptus grandis forests with the densities of 556 trees/hm2 and 1 667 trees/hm2.The results showed that:(1) The distribution of major nutrient element contents in various organs of the E.grandis with the 2 densities was nearly the same,and the ranked order was leaf＞tree trunk＞branch or branchlet＞fruit＞bark.(2) From the distribution of nutrient elements and organic matter in the trunk,P,K,Mg and Ca contents presented basically a trend of increasing with the trunk height increasing.And the organic matter content increased with the trunk height increasing in the low density stand,while the result was opposite in the high density stand.Furthermore,N content increased with the trunk height increasing in the low density stand,but the content in the high density stand exhibited a trend of decreasing at tirst,increasing then and increasing at the last.(3) From the distribution of biomass,the ranked order was tree trunk＞bark or branch＞branchlet＞ leaf＞fruit.And (4) The accumulated amounts of major nutrient elements in various organs under the 2 stand densities was nearly same.Ca content was the highest in the 2 kinds of plantations,followed by N,K,Mg and P contents.Ca content was 601.78 kg/hm2 in the low density stand and 1 204.43 kg/hm2 in the high density stand.