Peetoom Heida Isaac, Brown Charlotte, Dettlaff Margarete A, Oppon Kenneth J, Cahill James F
Department of Biological Sciences, CW 405 Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
AoB Plants. 2021 Feb 23;13(2):plab011. doi: 10.1093/aobpla/plab011. eCollection 2021 Apr.
Ecosystems are spatially heterogenous in plant community composition and function. Shrub occurrence in grasslands is a visually striking example of this, and much research has been conducted to understand the functional implications of this pattern. Within savannah ecosystems, the presence of tree and shrub overstories can have significant impacts on the understory herbaceous community. The exact outcomes, however, are likely a function of the spatial arrangement and traits of the overstory species. Here we test whether there are functional linkages between the spatial patterning of a native shrub and the standing biomass, community composition, and overall nutrient cycling of a neighbouring grassland understory communities within the Aspen Parkland of central Alberta, Canada. In a paired grassland-shrub stand study, we found the native shrub, , has relatively few stand-level impacts on the composition and standing biomass of the ecosystem. One factor contributing to these limited effects may be the overdispersion of shrub stems at fine spatial scales, preventing areas of deep shade. When we looked across a shrub density gradient and incorporated shrub architecture into our analyses, we found these shrub traits had significant associations with species abundance and root biomass in the understory community. These results suggest that stem dispersion patterns, as well as local stand architecture, are influential in determining how shrubs may affect their herbaceous plant understory. Thus, it is important to incorporate shrub spatial and architectural traits when assessing shrub-understory interactions.
生态系统在植物群落组成和功能上存在空间异质性。草原上灌木的出现就是一个直观的显著例子，并且已经开展了大量研究来了解这种模式的功能影响。在热带稀树草原生态系统中，树木和灌木上层植被的存在会对下层草本群落产生重大影响。然而，确切的结果可能取决于上层物种的空间排列和特征。在这里，我们测试了加拿大艾伯塔省中部白杨林地区一种本地灌木的空间格局与相邻草原下层群落的现存生物量、群落组成以及整体养分循环之间是否存在功能联系。在一项配对的草原 - 灌木林分研究中，我们发现本地灌木对生态系统的组成和现存生物量的林分水平影响相对较小。造成这些有限影响的一个因素可能是灌木茎在精细空间尺度上的过度分散，避免了形成深荫区域。当我们研究灌木密度梯度并将灌木结构纳入分析时，我们发现这些灌木特征与下层群落中的物种丰富度和根生物量存在显著关联。这些结果表明，茎的分散模式以及局部林分结构在决定灌木如何影响其下层草本植物方面具有重要作用。因此，在评估灌木与下层植物的相互作用时，纳入灌木的空间和结构特征非常重要。
