不同密度山桐子苗木地下竞争和地上竞争的定量研究

A Quantitative Study of Below-and-above-ground Competitions of Idesia polycarpa Seedlings at Different Planting Densities

利用通径分析方法,对山桐子3种栽培密度条件下苗木的地下竞争和地上竞争的关系及对总竞争的影响进行了研究。结果表明,山桐子苗木地下生物量、地上生物量和总生物量与栽植密度有明显的相关性。随着密度的减小,苗木的生物量增加,而各部分的竞争指数下降。同一密度,地上竞争指数大于地下竞争指数。由于植株生长时各部分相互影响,各竞争指数之间的相关性显著。但地下竞争和地上竞争对总竞争的影响存在着差异,通径分析可定量的反映出各部分的相对大小。山桐子苗木的地上竞争对总竞争的直接作用为0.5536-0.6533,明显大于地下竞争对总竞争的直接作用（0.4802-0.6228）。随着密度的降低,地上和地下竞争对总竞争的直接竞争作用均增大,但地上竞争占据主要作用。

To quantify the competition from above-and-below-ground plants, an experiment was conducted by use of seedlings of ldesia polycarpa. Path analysis was employed to study both the relationships between below-and-above-ground competitions, and their contribution to general competitions among individual seedlings at 3 different planting densities. The results showed that there were close relationships between below -ground biomass, above-ground biomass and total mass of Idesia polycarpa seedlings and the growing densities. With the decrease of the density, the seedling biomass increased while each part of the competition index fell. The above-ground competition index was greater than the underground at the same planting density. Due to the interactions between each part as the plants grew, the correlations among competition indexes were significant coefficients of path analysis, at 3 planting densities, showing that the direct influence intensity of above-ground competition on general competition wafted from 0. 5536 to 0. 6533, significantly greater than 0. 4802 - 0. 6228 of the underground competition. With the decrease of the density, the above-ground-and-below-ground competitions were intense, however, the above-ground competition had an important influence on the general competition.