Effects of canopy structure and species diversity on primary production in upper Great Lakes forests
Canopy structure and tree species diversity, shaped by succession, disturbance, and community composition, are linked to numerous ecosystem functions, including net primary production (NPP). Understanding of how ecosystem structural metrics are interrelated and mechanistically link to NPP, however, is incomplete. We characterized leaf area index (LAI), Simpson’s index of Diversity (D′, a measure of species diversity), and canopy rugosity (Rc, a measure of canopy physical complexity) in 11 forest stands comprising two chronosequences varying in establishing disturbance, and in three late successional communities. We related LAI, D′, and Rc to wood NPP (NPPw), and examined whether absorption of photosynthetically active radiation and light use-efficiency (LUE) link NPPw with ecosystem structure. We found that recovery of LAI and D′ was delayed following more severe establishing disturbances, but that the development of Rc was strikingly conserved regardless of disturbance, converging on a common mean value in late-successional stands irrespective of differences in leaf area index and species diversity. LAI was significantly correlated with NPPw in each stage of ecosystem development, but NPPw was only correlated with Rc in early successional stages and with D′ in late successional stages. Across all stands, NPPw was coupled with LAI and Rc, (but not D′) through positive relationships with light absorption and LUE. We conclude by advocating for better integration of ecological disciplines investigating structure–function interactions, suggesting that improved understanding of such relationships will require ecologists to traverse disciplinary boundaries.
KeywordsChronosequence Canopy structure Net primary production Canopy rugosity LiDAR Leaf area index Ecosystem structure Disturbance Succession Diversity Eastern temperate forest Light use efficiency
We thank two anonymous reviewers and Dr. Jeremy Lichstein, Handling Editor, for their thoughtful assessments of our paper. This study was supported by the National Science Foundation Division of Environmental Biology LTREB Award 1353908, the Division of Atmospheric and Geospace Sciences Award 1262634, and Emerging Frontiers Award 1550650. RTF was supported by United States Department of Agriculture McIntire-Stennis Award CONS00981. We acknowledge the University of Michigan Biological Station for facilities support.
Author contribution statement
CMS, LEN, KJN, and CMG conceived and designed the experiments. CMS, LEN, and CMG performed the experiments. CMS, RTF, and CMG analyzed the data. All authors wrote the manuscript and provided editorial advice.
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