红砂根系分叉数和分支角度权衡关系的坡向差异

根系构型是决定根系分布及其对土体搜索效率的重要因素, 是植物与资源环境异质性相互适应的结果。利用ArcGIS建立研究区域的数字高程模型(digital elevation model), 采用全根系挖掘法, 研究了祁连山北坡荒漠草原不同坡向红砂(Reaumuria songarica)根系分叉数和分支角度的关系。结果表明: 不同坡向梯度草地群落的盖度、密度、高度和土壤含水量呈不同的变化趋势(p < 0.05), 红砂种群的密度、高度和根冠比等生物学特征的变化规律存在差异(p < 0.05); 不同坡向红砂根系分叉数和分支角度的相关性存在差异(p < 0.05), 在南坡和北坡红砂根系分叉数和分支角度之间存在极显著的负相关关系(p < 0.01), 在东坡和西坡根系分叉数和分支角度之间存在显著的负相关关系(p < 0.05), 红砂根系分配给根系分叉数和分支角度的资源存在着“此消彼长”的权衡关系; 随着坡向由南坡向西坡、东坡、北坡转变, 红砂根系分叉数和分支角度回归方程的标准化主轴斜率逐渐减小(p < 0.05), 红砂根系构型模式由扩散型转向聚集型。不同坡向红砂根系合理权衡连接长度和分支角度的资源配置模式, 反映了异质生境中植物种群应对资源多重竞争的环境生态适应机制。

Trade-off relationship between root forks and branch angle of Reaumuria songarica on different aspects of slopes

Aims Root architecture is a major determinant in root spatial distribution and soil searching efficiency, may reflect plant strategies to adapt to the environments. Our objective was to examine the relationship between root forks and branch angle of Reaumuria songarica in response to slope aspects in the northwest of China.Methods The study site was located in desert grasslands on the northern slope of Qilian Mountains, Gansu Province, China. Survey and sampling were carried out along 20 belt transects. It were set up on sites of four different slope aspects at intervals of 30 m vertically from elevation 1940 m of the study area moving upward, 6 plots were set up flatly on site of each belt transect at intervals of 20 m. A handheld GPS was used to record longitude, latitude and altitude of each plot. ArcGIS was used to set up digital elevation model to extract the information of elevation, aspect, and slope for each plot. The traits of plant communities were investigated and 1 individual’s samplings of R. songarica were used to measure the root forks, root length and root branch angle in laboratory in each plot, and biomass of different organs was measured after being dried at 80 °C in an oven. The 120 plots were categorized into groups of south, west, east, and north aspects of slopes, and the linear regression analysis was then used to examine the trade-off relationship between root forks and branch angle in various groups.Important findings The results showed that with the slope aspect turned from south, west, east to north, the density, cover, height, above biomass and soil moisture content of the plant community displayed a pattern of initial increase, while the height, root-shoot ratio, root branch angle of R. songarica displayed a pattern of initial decrease, and the density, specific root length, root forks increase. The number of root forks was negatively associated with the branch angle, but the relationship varied along the aspect gradient (p < 0.05). There was a highly significant negative correlation (p < 0.01) between the root forks and branch angle on north slope and south slope, whereas less significant (p < 0.05) on the east slope and west slope. There is a trade-off relationship between the root forks and link length. In addition, when the slope aspect changed from south to west, east and north, the standardized major axis slope of regression equation in the scaling relationships between root forks and branch angle decrease (p < 0.05), indicating that the root architecture model of R. songarica by diffusion to gather. Consequently, the patterns of resource allocation between root forks and branch angle in different slope habitats reflected the mechanism of environment adaptation under conditions of multiple competitions for resources in plant populations.