Life cycle and masting of a recovering keystone indicator species under climate fluctuation
Ecosystem health and sustainability, to a large degree, depend on the performance of keystone or dominant species. The role of climate on population dynamics of such species has been extensively examined, especially for health indicator species. Yet the life-cycle processes and response lags for many species could complicate efforts to detect clear climate signals. Longleaf pine (Pinus palustris Mill.) is such a keystone tree species in the southeastern United States that has declined in both abundance and distribution during the past century. Despite research efforts on multiple fronts, the mechanisms behind the large spatial and temporal fluctuations in cone production that affects its regeneration are largely unknown. On the basis of long-term (15–56 yr) monitoring data at 10 sites across the species’ native range, we examine the spatial and temporal patterns in cone production and possible climatic effects on those patterns using the information-theoretic approach. Cone production exhibited great variation across sites and years, and long-term data revealed a weak, ca. 3 yr cycle (4 in one case) across the native range. The effects of climate were rather complex, most likely due to a mismatch between the prolonged cone-production life-cycle process and climatic fluctuation. Spatially, sites close to each other generally showed similar physical conditions and temporal trends in cone production. Across sites within longleaf pine’s range, moderate climate conditions appear to promote cone production. At most sites, there was an increasing trend in cone production, but how such a trend might be linked to climate change requires further investigation.
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