Heterogeneity creates borders, limits and contrasts between patches. In turn, this pattern generates new processes. Linked to heterogeneity, ecological systems have limits where layout is essential to understanding system organisation. This study analysed internal heterogeneity in natural grassland using: (1) estimation of species replacement in space, and (2) identification of transitional zones and definition of their ecological features in an extremely flat area of the Flooding Pampa, Argentina. Transition analysis was conducted at three sites; 77 plots in total. In each plot, all species, their cover percentage and the proportion of bare soil were recorded and soil samples (0–20 cm depth) measured for pH and electrical conductivity. With floristic data, we explored the relationship between pairwise similarities in community structure and pairwise differences in space, adjusting similarity as a linear or non-linear function of geographical distance. We then conducted a cluster analysis to identify transitional zones, which were associated with large vegetation units described for the Flooding Pampa. Floristic composition in transitional zones was analysed according to the proportions of species and combinations characteristic of the different plant communities. Finally, we synthetised topo-edaphic measured information with a Principal Component Analysis to analyse transitional zone environmental properties. Joining hierarchical classification methods and Indicator Species Analysis for single species and combinations, we highlighted internal heterogeneity, often not noticed in these environments. Rotational livestock grazing contribute to heterogeneity that is typical of these grasslands. Knowledge about transitional zones strongly supports the development of management strategies to prevent grassland degradation.

异质性在补丁之间产生边界、限制和对比。反过来，这种模式会产生新的流程。与异质性相关，生态系统在布局对于理解系统组织至关重要的地方存在局限性。本研究使用以下方法分析了天然草地的内部异质性：(1) 空间物种更替的估计，以及 (2) 阿根廷洪泛潘帕极端平坦地区过渡带的识别及其生态特征的定义。在三个地点进行了转变分析；共77个地块。在每个地块中，记录所有物种、它们的覆盖率和裸土比例，并测量土壤样品（0-20 厘米深度）的 pH 值和电导率。有了植物区系数据，我们探讨了社区结构的成对相似性与空间成对差异之间的关系，将相似性调整为地理距离的线性或非线性函数。然后，我们进行了聚类分析以确定过渡区，这些过渡区与为洪水泛滥的潘帕草原描述的大型植被单元相关。根据不同植物群落的物种比例和组合特征，分析了过渡带的植物区系组成。最后，我们用主成分分析合成了地形测量信息，以分析过渡带的环境特性。结合单一物种和组合的分层分类方法和指标物种分析，我们强调了内部异质性，在这些环境中通常不会注意到。轮牧放牧导致了这些草原的典型异质性。有关过渡区的知识有力地支持制定管理策略以防止草地退化。