Can We Bank on Forest Seed Banks
Forest Service scientists used a 63-year chronosequence of forest stands that are distributed throughout northern Pennsylvania to assess variability in seed bank richness and abundance. Unlike prior seed bank studies, the sampling design and analyses that were used enabled scientists to test not only variability over time, but also variability within and among sites of different age classes (e.g., young versus old stands). This work corroborates prior work that documented diminishing seed bank richness and abundance over time and delivers the novel finding that even across sites experiencing similar histories, seed bank composition grows increasingly dissimilar and less predictable as sites age.
Seed banks—viable seeds buried in soils—serve as taxonomic and genetic diversity reservoirs buffering plant populations from disturbance. Existing studies show that differential seed longevities govern seed bank diversity; seeds of most species survive up to a few years while others persist for decades. Nevertheless, we lack a general understanding of how seed bank diversity varies across space and time.
Elucidating spatiotemporal variation in seed bank composition is vital to forest renewal after disturbance. In 39 forest stands, aged 43 to 106 years post-disturbance, which are distributed across northern Pennsylvania, Forest Service scientists found that seed bank richness and abundance steadily declined beginning about age 50 with sites 95 years old or older characterized by species with long-lived seeds. Composition at older sites was nevertheless considerable, with older sites being dissimilar from younger sites and each other.
These results suggest that despite strong effects of differential seed longevities, intersite seed colonization, and extinction-event variation ultimately yields strikingly different communities. This work provides forest managers important information for maintaining diverse forests as it demonstrates that banking on recovery from seed banks may be challenging, because outcomes are unpredictable and difficult to manage.
Forest Service Partners