水分驱动下茵陈蒿(Artemisia capillaris Thunb.)地上生物量模型与异速生长特征

构建生物量预估模型,探究生物量在各器官中的分配策略和异速生长关系及其对环境因子的响应,对理解植物群落结构、功能、碳储存和分配机制具有重要意义。本研究以内蒙古荒漠草原常见种茵陈蒿(Artemisia capillaris Thunb.)为对象,在不同水分处理下,利用易测指标,如株高、基径、分枝数、冠幅和生物量等参数建立生物量模型,采用标准化主轴分析法分析其异速生长关系。结果表明:在不同水分处理下,茵陈蒿的最佳生物量预估模型的变量选择不同;不同水分处理下茵陈蒿各器官间、各器官与地上生物量间的异速生长关系不同,但相对于自然降水量,增水和减水50%下均为等速生长,这说明在不同水分条件下茵陈蒿对各器官间的资源配置存在权衡策略,符合最优分配假说;而在极端气候条件下,各器官对资源的竞争会变弱;在荒漠草原中,对草本植物进行生物量模拟,选择预测变量和方程模型时,应考虑生长季降水量。本研究可为荒漠草原草本植物生物量预估模型的建立和异速生长关系对环境因子适应的理解等提供方法支持及理论依据。

Aboveground biomass modeling and allometric growth characteristics of Artemisia capillaris Thunb. under different water availabilities.

Establishing plant biomass models to explore plant allocation strategy and allometric growth relationships under various environments is of importance for better understanding plant community structure and function,and the storage and allocation mechanism of carbon. An in situ field experiment was conducted to examine the effects of water availability on plant biomass and allocation strategy in a desert steppe in northern China. Several key but easily measured parameters of a common species,Artemisia capillaris Thunb.,in the desert steppe,including height,basal diameter,number of branches,crown,and biomass under different precipitation levels were used to construct plant biomass models. The allometric growth relationship of A. capillaris was analyzed using a standardized major axis regression. The results showed that the optimal parameters for biomass models along the gradient of water availability changed a lot. The allometric growth relationships within plant organs and that between plant organ and aboveground biomass were quite discrepant,with isometric growth relationships under extremely increased and decreased 50% precipitation amounts relative to the ambient. It indicated that there was a tradeoff of carbon allocation between plant organs under different water conditions,in accordance with the hypothesis of the best optimal resource allocation. However,the allocation competition may attenuate under extreme climatic conditions. The findings suggest that it is necessary to incorporate environmental factors such as precipitation for conducting biomass models of herbs in desert steppe. Our results can provide methodological support and theoretical basis for constructing bio-mass assessing models and understanding the adaptation of allometric growth to environment for herbs in arid ecosystems.