Community resilience in the face of fire: Analyzing the effects of plant functional types and dominant species in a semi-arid shrubland field experiment

LIPOMA MARIA LUCRECIA; CUCHIETTI ANIBAL; GURVICH DIEGO; PEREZ SOL; DÍAZ SANDRA

Portland

Congreso; 97th Annual Meeting. Life on Earth: Preserving, Utilizing, and Sustaining our Ecosystems; 2012

Ecological Society of America

Ecosystems are subject to different disturbances that affect their structure, function and viability. The ability of a natural system to return to a primary state after a disturbance is known as resilience. According to different views, resilience can be influence by the resource-use strategies of the plant functional types (PFTs) that form the community or by the existence of functional redundancy within PFTs. The goal of this study was to investigate how PFTs and their dominant species affect the resilience of a mountain shrubland after a fire. We took advantage from a pre-existing long-term removal experiment in which either whole PFTs or the dominant species within them were removed for 10 years. We sampled species and PFTs covers during the first growth season after fire (2010). The covers before and after fire were then compared by two analyses. To test whether functional redundancy increased the resilience we analyzed the existence of functional compensation inside PFTs comparing the cover values and proportion of cover of dominant and subordinated species of the PFT. To test whether PFTs with different resource-use strategies affected recovery, we compared the resilience at PFT-level and species-level, estimated on the basis of Euclidean distances in a DCA. No functional compensation was observed in any of the PFTs analyzed (deciduous shrubs, graminoids, perennial forbs and annual forbs). Besides, shrubs and perennial forbs, and principally their dominant species, recovered the fastest, although the mechanisms were different. Graminoids was the FTP that recovered less. Fire intensity and regeneration by species remaining from the post-fire stage appeared to be the factors that most influenced the recovery of this community. The second analysis showed that, at the species-level, conservative species were the most resilient and acquisitive species the least resilient, but the inverse was observed at the level of PFTs. Our study did not support the resilience by functional redundancy hypothesis. It did support the hypothesis that links resilience with the functional identity of dominant plants. However, regeneration traits rather than vegetative traits appeared as the most relevant to explain this response.