琵琶柴不同分支序级根系生物量分配格局的坡向差异

Difference in biomass allocation pattern among different branch orders in Reaumuria soongorica with slope aspects

生物量分配模式影响植物获取资源以及竞争能力,不同序级根系分支生物量分配格局对理解植物的表型可塑性有重要意义。本研究利用Arc GIS建立研究区域的数字高程模型,采用全根系挖掘法,研究了祁连山北坡荒漠草原不同坡向琵琶柴（Reaumuria soongorica）1～3级根系的生物量分配格局。结果表明：不同坡向草地群落的盖度、密度、高度、物种丰富度、地上生物量和土壤含水量呈不同的变化趋势（P〈0.05）,琵琶柴种群的密度、高度和根冠比等生物学特征的变化规律存在差异（P〈0.05）;随着坡向由南坡转向西坡、东坡和北坡,琵琶柴1级根生物量比例呈逐渐增加趋势（P〈0.05）,2级和3级根生物量比例呈逐渐减小趋势（P〈0.05）;琵琶柴1级根生物量的增加速度大于2级和3级根的增加速度,2级与3级根生物量近等速增长。不同坡向琵琶柴根系合理权衡各级根系资源配置模式,反映了异质生境中植物种群应对资源多重竞争的环境适应机制。

Biomass allocation pattern affects the gaining recources and competition ability of plant. Elucidation of the biomass allocation patterns among different root branch orders is impor- tant for understanding the phenotypic plasticity of plants under different habitats. In this study, we aimed to study the biomass allocation patterns of the first three root branch orders for Reau- muria soongorica in response to slope aspect change in a desert grassland on the northern slope of Qilian Mountains, Northwest China with the method of whole root system excavation and with ArcGIS to construct the digital elevation model for the study sites. The results showed that the coverage, density, height, species richness, aboveground biomass and soil moisture content of the plant community exhibited different variation tendencies in different slope aspects （P〈0.05）. The change patterns among the density, height, root-shoot ratio of R. soongorica varied with slope aspects （P〈0.05）. With the slope aspect turning from south to west, east and north, the propor- tion of the first-order branch biomass of R. soongorica gradually increased （P〈0.05） , while the proportion of the second-order and third-order branch biomass decreased （P〈0.05）. An isometric relationship was found between second-order branch biomass and third-order branch biomass in plots within each slope, whereas the growth speed of first-order branch biomass was greater than that of second-order and third-order branch biomass. The root resource allocation mode by reason- able tradeoff among different branch orders with changes in slope aspect of the habitat reflected the adaptation mechanism of plant populations to environment under conditions of multiple com- petition for resources.