Seed Bank Variation under Contrasting Site Quality Conditions in Mixed Oak Forests of Southeastern Ohio, USA

Christine J Small,Brian C Mccarthy

doi:10.1155/2010/419482

Christine J Small, Brian C Mccarthy

Open Access

https://doi.org/10.1155/2010/419482

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Abstract

Seed bank composition was sampled in 192–2.5 m2quadrats, established in six regenerating clearcut (∼7 years) and six second-growth (∼125 years) mixed-oak forest stands in southeastern Ohio. Seed bank and aboveground composition diverged markedly (Sørensen's coefficient <10%), emphasizing the importance of fast-growing, early-successional germinants to early ecosystem recovery. Seed richness was significantly (P<.01) higher in clearcut stands, suggesting declining richness with stand age. Richness estimations 28%–60% higher than observed values demonstrated high seed bank heterogeneity, emphasizing the need for intensive sampling to assess temperate forest seed bank variation. Site quality (topographic aspect) strongly influenced seed bank composition, with greater importance of early-successional trees, thicket-forming shrubs, and nonnative species on mesic sites. Thus, forest seed banks are likely to play an important, site-dependent role in shaping competitive environments for commercially important timber species after harvesting and soil disturbance and have the potential for marked influence on postharvest forest development.

Highlights

Management priorities in US National Forests have changed markedly over the past century, with current policy emphasizing management of forests as intact and functioning ecosystems [1, 2]
Mature second-growth forests are dominated by mixed oaks (Quercus spp.) and hickories (Carya spp.) on ridgetops and south-facing slopes and mesophytic species (e.g., Fagus grandifolia, Liriodendron tulipifera, Acer saccharum, Fraxinus americana, and Prunus serotina) on lower and north-facing slopes [41]
Our examination of buried seed distribution across naturally regenerating and mature second-growth mixed oak stands showed four pronounced trends: (1) seed bank composition diverged markedly from that of aboveground vegetation, (2) observed seed bank richness was lower in later successional forests than in recently harvested stands, (3) despite intensive sampling, richness estimators and species-area curves indicated high seed bank variability, supporting previous assertions that temperate forest seed banks often are undersampled, and (4) topographic aspect strongly influenced seed bank composition, including the prevalence of nonnative plant species

Summary

Introduction

Management priorities in US National Forests have changed markedly over the past century, with current policy emphasizing management of forests as intact and functioning ecosystems [1, 2]. This ecosystem-based approach seeks to maintain forest productivity and production of goods and services, while protecting the physical, chemical, and biological processes associated with healthy ecosystem function (e.g., soil and water quality, nutrient cycling, and biological diversity) [2,3,4]. Complete removal of overstory trees and soil disturbance during traditional stem-only or whole-tree clearcutting has the potential to significantly alter stand development patterns by reducing or eliminating advance regeneration (e.g., formerly suppressed seedlings and saplings and root- and stumpsprouts) and increasing the importance of germinating seeds during early ecosystem recovery [3, 10, 11]

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