Temporal and spatial differentiation in seedling emergence may promote species coexistence in Mediterranean fire‐prone ecosystems

Abstract

Mediterranean ecosystems are hotspots of species richness where fire is one of the key processes influencing their structure, composition and function. Post-fire seedling emergence constitutes a crucial event in the life cycle of plants and species-specific temporal and spatial patterns of seedling emergence have been hypothesized to contribute to the high diversity in these ecosystems. Here we study the temporal and spatial patterns of seedling emergence observed for the four dominant species (Cistus albidus, Ulex parviflorus, Helianthemum marifolium, Ononis fruticosa) after an experimental fire in a Mediterranean gorse shrubland. In a first analysis we compared the timing of emergence of each species using the Kaplan-Meier method. The spatial component of seedling emergence and the spatiotemporal relationship between different cohorts of the same species were analyzed using recent techniques of spatial point pattern analyses. We found a bimodal temporal pattern of emergence. Emergence of Cistaceae species (H. marifolium and C. albidus) occurred predominantly early after the fire while Fabaceae (O. fruticosa and U. parviflorus) emerged mainly during the following autumn. Individually, all species showed an aggregated spatial pattern and, when testing for pair interactions, we found that the clusters of individual species were spatially segregated. Additionally, the clusters of individual species showed an internal spatial structure where seedlings of different cohorts were spatially segregated. Theoretical models predict that these patterns will promote species coexistence. We identified a number of mechanisms that all have the potential to contribute to the observed pattern formation. However, the potential interaction among these mechanisms are complex and not easy to predict. Our analyses take a significant step forward in studying seedling emergence in fire prone ecosystems since, to our knowledge, this is the first time that both spatial and temporal patterns of all dominant species have been studied together.

Changes in spatial point patterns of pioneer woody plants across a large tropical landslide

“…According to this method, we assumed that the patterns in each of the four plots were independent samples or "replicates" from a larger pattern per subzone (Law et al, 2009). Additionally, this approach enabled us to make inferences in relation to whole subzones rather than merely describing the spatial patterns of individual plots De Luis et al, 2008).…”

“…Postfire colonization of new opportunistic species usually causes dramatic changes in the spatial patterns of plant communities, increasing either aggregation or regularity (Rebertus et al, 1989). Repulsion between the spatial patterns of these species may also arise as a consequence of negative interactions among them (De Luis et al, 2008).…”

Spatial associations among tree species in a temperate forest community in North-western Spain

“…However, while it is relatively easy to confirm that the spatial pattern of a given species is non-random, it is more difficult to analyse the spatial association between species (Wiegand and Moloney, 2004;Wiegand et al, 2007a;Wang et al, 2010). As a consequence, few studies have investigated spatial interactions between all dominant species in a plant community (e.g., Nishimura et al, 2002;Rozas, 2006;Getzin et al, 2006Getzin et al, , 2008Kubota et al, 2007;De Luis et al, 2008;Zhang et al, 2010;Wang et al, 2010). However, such studies are needed to advance our understanding on the importance of spatial patterns for the assembly, dynamics and functioning of such ecosystems.…”

The role of seed traits as segregation factors of hybrids in wild populations ofCistus(Cistaceae)

“…Then, the exposed spatial and temporal segregation of the regeneration niche might have not only an ecological meaning in terms of niche separation (Silvertown 2004) but also some adaptive advantage of hybrid lineages to escape from fire by farther seed dispersal and deeper seed burial before the fire (Naveh 1975;Chambers et al 1991). Temporal and spatial segregation in seedling recruitment has been already suggested as a strategy to facilitate the coexistence of pyrophytic plant species including C. albidus in Mediterranean fire-prone environments (De Luis et al 2008). The smaller hybrid seeds might reach deeper soil levels than bigger ones.…”