密度对大叶相思幼林地上竞争和地下竞争的影响

Density Effects on Interactions Between Above-and Belowground Competition in Young Acacia auriculaeformis Stands

对不同密度大叶相思Acacia auriculaeformis幼林林木各器官(根、枝、叶、干)平均干质量、生物量及竞争进行了研究.结果表明,枝和叶干质量随着密度的增大呈减小趋势,低密度林分林木的干和根的平均干质量均大于中密度和高密度林分.低密度林分林木的平均个体干质量为干>根>叶>枝,而中密度和高密度林分林木为干>根>枝>叶.各密度林分林木的平均地上与地下干质量之比分别为3.51、4.66和4.40,说明幼苗对光具有较强的需求和竞争能力.林分生物量随着密度的增加而显著增加.地上竞争指数和总竞争指数为高密度林分>中密度林分>低密度林分,地下竞争指数为高密度林分>低密度林分>中密度林分.各林分的地上竞争指数明显大于地下竞争指数.苗木地上部分干质量与地下部分干质量之间及地上竞争指数与地下竞争指数之间呈极显著正相关.

Mean individual dry mass of tree organs, stand biomass and competition were studied in young Acacia auriculaeformis stands with different densities. The results showed that branch and leaf dry mass decreased with increasing density, and dry mass of stem and root in the low-density stand were greater than those in the middle- and high-density stands. Mean organ dry mass in the low-density stand varied in the order of stem 〉 root 〉 leaves 〉 branches, whereas those in the middle- and high-density stands were stem 〉 root 〉 branches 〉 leaves. Ratios of mean aboveground dry mass to mean belowground dry mass in low-, middle- and high-density stands were 3.51,4. 66 and 4.40 ,indicating that the young seedlings had strong demand and competition ability for light. Stand biomass significantly increased with increasing density. The orders of aboveground and total competition indexes were the high-density stand 〉 the middle- density stand 〉 the low-density stand, whereas the order of belowground competition index was the high- density stand 〉 the low-density stand 〉 the middle-density stand. Aboveground competition index was significantly greater than belowground competition index in each stand. There were significantly correlations between aboveground organ dry mass and belowground organ dry mass and between aboveground competition index and belowground competition index.