林木分化对兴安落叶松异速生长方程和生物量分配的影响

Differentiation of stand individuals impacts allometry and biomass allocation of Larix gmelinii trees

林木因对资源竞争而产生分化,从而影响林木的异速生长方程和生物量分配,但其影响程度还不清楚。采用林木相对直径法将38株兴安落叶松(Larix gmelinii)样木在林分中的分化等级分为优势木、中等木和被压木,量化林木分化对林木异速生长方程和生物量分配的影响。结果显示:生物量组分异速生长方程多以胸径(DBH)为自变量为好,但以枝下高处的树干直径为自变量估测其枝、叶生物量时更精确。在一定的胸径范围内,同一胸径下不同林木分化等级的地下部分各组分生物量没有显著差异(P>0.05),但优势木分配更多的生物量给枝和叶,中等木比优势木分配更多的生物量给树干,中等木比被压木分配更多的生物量给地上部分,而且被压木和中等木的树高显著高于优势木。除根茎生物量之外,不同林木分化等级的生物量组分(包括枝、叶、树干和根系)的相对分配比例无显著差异(P>0.05),根冠比保持相对稳定。这些结果表明,主要由竞争而引起的林木分化改变了兴安落叶松地上生物量组分的异速生长和分配,但其相对分配格局较为保守。

Differentiation of stand individuals results from the competition of limited resources and thus affects allometry and allocation of tree biomass,but the extent to its impact has rarely been quantified. In this study,38 Larix gmelinii trees,including 15 dominant,16 intermediate,and 7 suppressed trees that were classified using a relative diameter method,were harvested for quantifying the effect of tree differentiation in the stand on the allometry and allocation of biomass. The results showed that the diameter at crown base was the most reliable predictor for branch and foliage biomass,whereas the diameter at breast height（ DBH） was the best predictor for the other biomass components. For a specific value within a certain range of the DBH, the allometric models for belowground biomass components did not differ significantly among the tree differentiation classes（ P〉0. 05）. However,the dominant trees allocated more biomass to branch and foliage components,whereas the intermediate trees allocated more biomass to stem component than the dominant, and more biomass to aboveground component than the suppressed. The tree height of the suppressed and intermediate trees was significantly greater than the dominant for a given DBH. The proportions of all the components except for stump to the total biomass did not differ significantly（ P〉0. 05） among the tree differentiation classes. The root shoot ratio was relatively constant for allthe tree-differentiation classes. These results suggest that the differentiation of stand individuals in the larch trees mainly caused by resource competition diverts the allometry and allocation of the aboveground biomass components,but the relative allocation pattern is conservative.