Spatial Patterns of Canopy Disturbance, Structure, and Species Composition in a Multi-Cohort Hardwood Stand

Scott Ford,Justin Hart,Jonathan Kleinman

doi:10.3390/f8030093

Abstract

Multi-cohort stands are increasingly recognized and valued because of their biological functioning, biological diversity, and resistance and resiliency to perturbations. These forest ecosystems are epitomized by multiple age classes, and often contain multiple canopy layers, a range of tree size classes, and large amounts of woody debris. Disturbance history reconstructions in multi-cohort stands provide an understanding of the processes that create these systems. In this study, we documented structure and composition, and used dendroecological techniques to reconstruct disturbance history on a 1 ha plot in a multi-cohort hardwood stand in the Fall Line Hills of Alabama. The stand was dominated by Quercus alba L. and Liriodendron tulipifera L. Mingling index and stem maps indicated that most species were well dispersed throughout the stand, with the exception of L. tulipifera and Carya tomentosa (Poiret) Nuttal, which were relatively clustered. The oldest trees in the stand established in the 1770s, however, the largest recruitment event occurred ca. 1945 in conjunction with a stand-wide canopy disturbance. We posit that spatial heterogeneity of canopy removal during this event was largely responsible for the observed compositional and spatial complexity documented in the stand. In addition to the 1945 event, we recorded another stand-wide canopy disturbance in 1906 and 84 gap-scale disturbance events from 1802 to 2003. The conditions documented in the stand can be used as a benchmark to guide the creation and maintenance of complex multi-cohort stand characteristics, an increasingly popular management goal.

Highlights

Traditional forest management practices have often been criticized for creating overly homogenous stands and reducing ecosystem complexity [1,2,3,4]
This study presents the first analysis of spatiotemporal patterns of canopy disturbance in a multi-cohort hardwood stand in the Alabama Fall Line Hills
To optimize the effects of these management operations, silvicultural prescriptions must be informed by quantifications of the historical disturbance regime in the appropriate biophysical settings [17]

Summary

Introduction

Traditional forest management practices have often been criticized for creating overly homogenous stands and reducing ecosystem complexity [1,2,3,4]. Ecosystems with high levels of complexity, such as late-successional or multi-cohort forest stands, often have comparatively high levels of resistance and resilience to environmental perturbations [6,7] Contemporary societal pressures such as alien species introductions, urbanization, fragmentation, and poor land management practices have caused many forested ecosystems to deviate from the natural processes (i.e., disturbance regimes) that create and maintain complex stand characteristics [8]. Restoring these processes with appropriate management efforts may be necessary to promote complexity and associated ecosystem functions [4,6,9]. Promoting structural diversity is an increasingly popular management goal [10,11] and spatial patterns of biomass and light are important considerations of complexity enhancement projects [12,13]

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Conclusion