Data from: Resprouter fraction in Cape Restionaceae assemblages varies with climate and soil type

While fire-induced changes in biodiversity are well documented, less is known about how fire impacts life-history variation and diversity of functional traits that represent distinct strategies for persistence in fire-driven ecosystems. One example is the dichotomy in which ‘resprouter’ species usually survive fires to produce new growth, while ‘reseeder’ species perish and re-establish from seed. Variable relative numbers of reseeder and resprouter species in local assemblages of Restionaceae (Poales) of the Cape Floristic Region (CFR), and their high species richness and endemism, make this family representative of the region's functional, taxonomic and ecological diversity. We investigate how the proportion of resprouter species (resprouter fraction) changes among edaphic conditions and along a climate moisture (i.e. aridity) gradient that integrates annual precipitation (range 130–1300 mm) and potential evapotranspiration (range 3–8 mm m−2 day−1). We sampled local assemblages using a stratified-random design that fully spanned the environmental conditions of the CFR. As climate moisture across sites with infertile soils increased, so did resprouter fraction. Resprouters may increasingly dominate reseeders as moisture increases under conditions in which productivity is generally limited. This suggests the explanatory hypothesis that in these conditions, greater moisture accelerates both biomass accumulation (fuel) and fire frequency, providing an advantage to resprouters. However, we found no evidence for increasing resprouter fraction with increasing climate moisture on more fertile soils. This statistical interaction suggests the possibility that moisture affects resprouter fraction dependent on soil fertility, potentially through: (i) impacts on species composition, if soil type acts as an environmental filter or promotes biotic interactions, and/or (ii) impacts on fire dynamics, potentially through fuel load drying rates. Future research should include a comprehensive fire model for the CFR, to enable direct examination of relationships of life-history and functional traits across variation in fire dynamics. Additionally, our results indicate that we need both (i) demographic studies on plant establishment, growth rates and survival, and (ii) field experiments that address how environmental and biotic filters affect species composition across variable fire regimes. These together should facilitate mechanistic interpretation of how fire mediates life-history variation and diversity of functional traits in the CFR.尽管火对生物多样性的影响已有大量研究记录，但人们对火如何影响火驱动生态系统中代表不同存续策略的生活史变异与功能性状多样性的认知仍较为匮乏。其中一个典型的二分法案例为：‘萌枝复苏种（resprouter）’通常可在火灾后存活并萌发新枝，而‘种子更新种（reseeder）’则会在火灾中死亡，依靠种子重新定植。 开普植物区（Cape Floristic Region, CFR）内帚灯草科（Restionaceae，禾本目Poales）的本地群落中，种子更新种与萌枝复苏种的相对丰度存在显著差异，且该科物种丰富度与特有性极高，因此其可作为该区域功能、分类与生态多样性的典型代表类群。 本研究旨在探究萌枝复苏种占比（resprouter fraction）在不同土壤条件下的变化，以及沿整合了年降水量（范围130–1300 mm）与潜在蒸散量（potential evapotranspiration，范围3–8 mm m−2 day−1）的气候湿度（即干旱度）梯度的变化规律。研究采用分层随机抽样设计（stratified-random design），全面覆盖了开普植物区的各类环境条件，并对本地植物群落进行了采样。 在土壤贫瘠的样地中，随着气候湿度升高，萌枝复苏种占比也随之上升。在生产力普遍受限的环境下，随着湿度增加，萌枝复苏种可能逐渐取代种子更新种占据优势。这指向一个解释性假说：在这类环境中，更高的湿度会同时加速生物量积累（即火灾燃料）与火灾发生频率，从而为萌枝复苏种带来生存优势。然而，在土壤更为肥沃的样地中，并未发现气候湿度升高会伴随萌枝复苏种占比上升的证据。 这一统计交互作用（statistical interaction）表明，气候湿度对萌枝复苏种占比的影响可能依赖于土壤肥力，其潜在途径包括：（i）若土壤类型作为环境过滤因子或促进生物相互作用（biotic interactions），则会影响物种组成；以及/或（ii）通过影响可燃物载量干燥速率进而改变火灾动态（fire dynamics）。未来研究应构建开普植物区的综合火灾模型，以直接探究火灾动态变化下生活史与功能性状间的关联。此外，本研究结果显示，我们还需开展两方面工作：一是针对植物定植、生长速率与存活情况的种群统计研究（demographic studies），二是探讨环境与生物过滤因子在可变火制度（fire regimes）下如何影响物种组成的野外实验。上述研究将共同推动对开普植物区中火如何介导生活史变异与功能性状多样性的机制性阐释。