地上竞争对林下红松生物量分配的影响

采用整株收获法研究林下红松地上、地下生物量分配特征及地上竞争对其生物量分配和生物量相对生长的影响。结果表明,(1)将整个树冠划分为等长的上、中、下三层,活枝生物量从上层到下层逐渐增加,而针叶生物量主要集中在树冠中下层且在中下层的分布无显著差异(P>0.05),随着地下生物量逐渐增加,小细根(<2 mm)、粗细根(2-5 mm)的比例逐渐减小,而粗根(>5 mm)所占比例逐渐增大;(2)地上竞争强度与胸径、树高呈显著指数相关(P<0.001),随着竞争强度增大,胸径和树高均逐渐减小,树高胸径比与竞争强度呈显著线性相关(P<0.05),而树冠比率与竞争强度之间无显著相关性(P>0.05);(3)随着竞争强度增大,树干生物量占整株生物量的相对比例逐渐减小,而细根(小细根和粗细根)生物量相对比例逐渐增大,活枝、针叶及粗根生物量相对比例与竞争强度相关性并不显著(P>0.05);(4)红松根冠比均值为0.15且根冠比并不受地上竞争的影响,茎叶比与竞争强度的相关性亦不显著(P>0.05);(5)地上竞争显著影响红松地上各器官生物量的相对生长,且竞争强度与生物量呈显著负相关(P<0.001)。

Effect of aboveground competition on biomass partitioning of understory Korean pine (Pinus koraiensis)

Competition is an important factor in biology and plant-plant interactions has inspired an increasing concern in recent years. In plant communities, competition is defined as the interaction between individuals, brought about by limited resources. Aboveground competition is usually size-asymmetric: the bigger individuals have a disproportionate advantage in competing for light than the smaller ones. This study deals with biomass allocation patterns and aboveground competition influences on biomass partitioning and allometric equations of understory Korean pine (Pinus koraiensis). The results will contribute to understanding the mechanisms of aboveground competition and provide a theoretical guide for effective utilization and protection of Korean pine. The results show that: (1) When dividing live crown into three equal layers (top, middle and bottom), live branch biomass increased from the top to the bottom layer, while needle biomass was highest in the middle and bottom layers of the crown. However, there was no significant difference between the needle biomass located at the middle and bottom layers (P>0.05). The relative proportion of coarse root (>5 mm) biomass increased while that of small fine root (<2 mm) and coarse fine root (2-5 mm) biomass both decreased with increasing total belowground biomass. (2) Stem diameter at breast height and tree height both showed a significantly exponential correlation with aboveground competition intensity (P<0.001). Breast-height diameter and tree height both decreased with increasing competition intensity. The ratio of tree height to breast-height diameter showed a significant linear relationship with competition intensity (P<0.05), whereas, there was no significant relationship (P>0.05) between competition intensity and crown ratio, which is defined as crown length divided by total tree height. (3) With increasing competition intensity, the relative proportion of stem biomass deceased while that of fine root (small fine root and coarse fine root) biomass increased. There was no significant relationship between competition intensity and the proportion of live branch, needle as well as coarse root biomass (P>0.05). (4) The average root to shoot ratio value was 0.15. This ratio was not affected by competition intensity (P>0.05). Similarly, the stem to needle biomass ratio also did not correlate with competition intensity (P>0.05). (5) Aboveground competition significantly affected the biomass allometry of aboveground biomass components and competition intensity showed a significant negative (P<0.001) correlation with biomass components. Thus, competition should not be disregarded in biomass studies. Regarding forest management, it is necessary to carry out tending operations to release the understory Korean pine trees from competition, in order to stimulate their growth, to obtain timber products and to protect the available germ plasm resource.