Wood net primary production resilience in an unmanaged forest transitioning from early to middle succession |
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Authors: | Christopher M Gough Christoph S Vogel Brady Hardiman Peter S Curtis |
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Institution: | 1. Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA;2. Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH 43210, USA;3. University of Michigan Biological Station, Pellston, MI 49769, USA |
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Abstract: | The mixed deciduous forests of the upper Midwest, USA are approaching an ecological threshold in which early successional canopy trees are reaching maturity and beginning to senesce, giving way to a more diverse canopy of middle and late successional species. The net primary production (NPP) of these forests is generally considered past peak and in decline, but recent studies show a striking resilience in the NPP trajectories of some middle and late successional forests; yet, the mechanisms controlling such temporal changes in NPP are largely unknown. At the University of Michigan Biological Station in northern Michigan, we used a ≥9-year continuous record of wood net primary production (NPP), leaf area index (LAI), canopy composition, and stem mortality in 30 forested plots to identify the constraints on wood NPP as a mixed forest transitions from early to middle succession. Although wood NPP decreased over time in most stands, the rate of decline was attenuated when the canopy comprised a more diverse assemblage of early and middle/late successional species. The mechanism for sustained NPP in stands with more species diverse canopies was the proliferation of LAI by intact later successional tree species, even as stem mortality rates of early successional trees increased. We conclude that projections of carbon sequestration for the aging mixed forests of the upper Midwest should account for species composition shifts that affect the resilience wood NPP. |
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Keywords: | Net primary production Succession Diversity Leaf area Forest Carbon cycling |
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