不同栽植方式下紫椴幼苗生物量分配及资源利用分析

 通过紫椴（Tilia amurensis Rupr.）幼苗在不同植距下纯栽和与落叶松(Larix gmelini)的混栽沙培试验，初次应用通径分析，研究紫椴幼苗生物量分配和资源利用机制，分析种内和种间竞争及其模式。研究发现总体上植距增大有利于紫椴根、茎、叶各器官的生长。通过通径分析说明，紫椴地下根系对总生长的贡献为0.236 1～0.286 9，地上茎、叶对总生长的贡献为0.732 5～0.775 8，地上部分的贡献是地下根系的2.95倍。表明紫椴幼苗对光具有较强的需求和竞争能力。紫椴和落叶松之间存在悬殊较大的生物量差距，落叶松的根、茎、叶生物量约是相应混栽紫椴的2、5、4倍。通过比较纯栽和混栽试验中的直接通径系数，与落叶松混栽后，紫椴对地下水分养分的竞争下降36.84%，对地上光照空间的竞争增大11.63%。随植距减小落叶松对紫椴的影响增大，紫椴根系生长受落叶松种间竞争影响不显著；地上茎、叶生长只在一定植距范围内受落叶松影响。紫椴与落叶松种间竞争是不同资源利用等级的两树种间的相互作用，以对称性地下竞争与落叶松“平等”地占有地下水分养分资源，从而受落叶松地下竞争较小；在一定空间范围内落叶松以非对称性竞争优先占有地上光照资源影响紫椴生长。

BIOMASS ALLOCATION AND RESOURCE USE OF TILIA AMURENSIS JUVENILE UNDER DIFFERENT PLANTING TREATMENTS

Biomass allocation, resources use and competitive pattern, the main contents in plant inter- and intra-specific competition research provide insight into the mechanism driving natural vegetation change and therefore, for better silviculture practices. In this study, we chose Amur linden (Tilia amuransis Rupr.), a dominant canopy species of the Pinus koraiensis coniferous-broadleaved forest and a commercially valuable species to address the following issues: (1) the aboveground and underground biomass allocation of Amur linden under different planting distance; (2) quantifying the effect of below- and above-ground biomass on the total biomass of the seedling; (3) to compare the allocation (or consumption) of aboveground and belowground resource in the inter- and intra-specific competition of Amur linden and Larix spp.; (4) analyzing the resource use and the competition pattern of the seedling. Experiments were designed for cultivated Amur linden juvenile pure and its mixture with Larix spp. Respectively on a sand groundmass (10 m (length), 20 m (width), 1 m (depth)) under different planting distance (including 10, 20, 30, 40 cm) in May 1997 at Mao'ershan experiment station of Northeast Forestry University, Heilongjiang province, China. The seedlings were watered and fertilized regularly to maintain growth under limited resources. At the end of September 1999, the seedling leaves, stems and roots were harvested and weighed separately to obtain the wet and dry biomass. Path analysis was applied to quantify the effect of below- and above-ground biomass on the total biomass of the seedlings, to determine the resource use and the competition pattern of the seedlings. Path analysis is a linear regression where the regression coefficient is standardized to decrease the correlativity among independents. Hence it may be applied to quantify the direct and indirect influence from the related belowground and aboveground growth to the total growth of Amur linden, and compare the relative importance of the two dependents to the independent. The biomass of root, stem, and leaf of the Tilia increased with growth space increase, with the exception of the 10 cm planting distance. Through path analysis, the contribution of belowground roots to the total growth is 0.236 1 0.286 9, that of stem and leaf is 0.732 5 0.775 8, which is 2.95 times of the former. The biomass between Tilia amurensis and Larix spp. differed significantly. The biomass of roots, stems and leaves of Larix spp. was approximately 2, 5, 4 times greater than those of the mixed Tilia amurensis. Through comparison of the direct path coefficient between mono-culture and mixed-culture experiment, we found that the competition ability of Tilia amurensis for underground water and nutrients was decreased by 36.84% and that for light and space was increased by 11.63% after mixed with Larix spp. The influence of the Larix spp. on Tilia amurensis increased with decrease in growth space. The influence from the intra-specific competition of Larix spp. on Tilia amurensis was not notable in terms of root growth while the growth of stem and leaf was influenced significantly only within the limited growth space in our experiment. The intra-specific competition of Tilia amurensis and Larix spp. is the interaction of two species which belong to different grade for resource utilization respectively. Although Larix spp. has a larger root system, Tilia amurensis still can acquire underground water and nutrients proportional to its size and can equally possess underground space through symmetric competition, so there is less underground competition from Larix spp. In aboveground competition, Larix spp. with its spatial advantage for aboveground growth, can asymmetrically compete the aboveground resource, by interception and capture more light from Tilia amurensis, which affects the growth of Tilia amurensis in limited spatial range.