Strategies to persist in the community: Soil seed bank and above-ground vegetation in Patagonian pine plantations

Abstract

Questions: In terms of biodiversity conservation, forest plantations are often considered problematic because they usually have negative effects on natural ecosystems. Soil seed banks could play an important role in restoring vegetation that was originally present, by recruiting species that have disappeared above-ground. We addressed this topic in plantations located in the Patagonian steppe by asking the following questions: Are richness, abundance and composition of steppe above-ground vegetation and soil seed bank affected by plantations? Is species composition of the above-ground vegetation and soil seed bank similar in plantations and in the steppe?. Location: NW of Chubut Province, Patagonia, Argentina. Methods: We selected three plantations located in the steppe, and delimited three sectors: steppe, plantation edge and plantation interior. We compared richness and abundance by species origin and growth form among sectors for the above-ground vegetation and soil seed bank compartments, using generalized linear mixed models. We compared species composition for each compartment and between them using permutational multivariate analysis of variance and non-metric multidimensional scaling. Results: In above-ground vegetation, we found a decrease in richness and abundance, and changes in composition from the steppe to the plantation interior. Richness and abundance of the soil seed bank did not show differences among steppe and the plantation sectors, although composition was different among them. Above-ground vegetation and soil seed bank species composition were always different; native perennial herbs and shrubs were predominant in the above-ground vegetation while exotic annual herbs dominated the soil seed bank. Conclusions: Our findings suggest that plant recruitment from the soil seed bank would not be sufficient for restoring depleted species pools in the above-ground vegetation of plantations. Therefore, actions promoting native species reestablishment and control of exotics should be considered to reach the aim of restoring biodiversity in former plantations.