Data from: Overdispersed spatial patterning of dominant bunchgrasses in southeastern pine savannas

Spatial patterning is a key natural history attribute of sessile organisms that frequently emerges from and dictates potential for interactions among organisms. We tested whether bunchgrasses, the dominant plant functional group in longleaf pine savanna groundcover communities, are non-randomly patterned by characterizing the spatial dispersion of three bunchgrass species across six sites in Louisiana and Florida. We mapped bunchgrass tussocks > 5.0-cm basal diameter in three 3×3-m plots in each site. We modeled tussocks as two-dimensional objects to analyze their spatial relationships while preserving sizes and shapes of individual tussocks. Tussocks were overdispersed (more regularly spaced than random) for all species and sites at the local interaction scale (< 0.3 m). This general pattern likely arises from a tussock-centered, distance-dependent mechanism e.g., inter-tussock competition. Non-random spatial patterns of dominant species have implications for community assembly and ecosystem function in tussock-dominated grasslands and savannas, including those characterized by extreme biodiversity.

空间格局（spatial patterning）是固着生物（sessile organisms）的核心自然历史属性，其通常由生物间的相互作用所产生，并决定着生物间相互作用的潜在发生潜力。本研究以长叶松稀树草原（longleaf pine savanna）地被群落（groundcover communities）中的优势植物功能群（plant functional group）——丛生禾草（bunchgrasses）为研究对象，通过对路易斯安那州与佛罗里达州6个样地内3种丛生禾草物种的空间分布特征进行表征，检验其空间排布是否具有非随机性。我们在每个样地内设置3个3米×3米的样方，对基径（basal diameter）大于5.0厘米的禾草簇（tussocks）开展定位测绘。本研究将禾草簇建模为二维对象（two-dimensional objects），在保留单个禾草簇尺寸与形态的前提下分析其空间关联特征。在局域相互作用尺度（<0.3米）下，所有物种与样地内的禾草簇均呈均匀离散分布（overdispersed，即空间排布较随机过程更为规整）。这一普遍性格局大概率源于以禾草簇为核心的距离依赖型调控机制，例如禾草簇间的竞争。优势物种的非随机空间格局对以禾草簇为主导的草原与稀树草原群落的组装过程及生态系统功能具有重要意义，其中也包括那些以极高生物多样性为特征的群落。