Group selection and gap-based silvicultural systems are often proposed to promote compositional and structural heterogeneity across forest landscapes. The gap environment creates gradients of resources, especially light and moisture, that are important for maintaining and enhancing tree species diversity. To advance understanding of spatial variability of tree regeneration in forest gaps, seedlings and saplings of yellow birch ( Betula alleghaniensis Britton) and eastern hemlock ( Tsuga canadensis (L.) Carrière) were mapped in 49 group-selection openings with diameters of 1, 1.5, and 2 times canopy tree height (22. m), 9. years after the openings were created. We used Ripley's K, kernel density estimates, and raster-based local statistics to analyze spatial point patterns. Our results indicate that spatial patterns in the openings were mostly aggregated. The southern edges of the largest openings contained the highest magnitude of yellow birch and eastern hemlock per unit area. Moisture availability and opening size appear to be important factors underlying regeneration success in this study. Over time, the spatial patterns of these species may shift as the southern locations become less suitable for the shade mid-tolerant yellow birch. Continued monitoring and additional treatments, such as gap expansion along southern borders, will likely be necessary in order to ensure underrepresented species successfully reach maturity.
Bibliographical noteFunding Information:
Funding for this project was provided by the McIntire-Stennis Cooperative Forestry Research Program and Ecosystem Science Center and School of Forest Resources and Environmental Science at Michigan Technological University. Joshua Shields, Linda Nagel, James Schmierer, and Jon Neuendorff were instrumental in the establishment and implementation of the silvicultural trial. We would also like to thank Rachel Mason for her invaluable contributions to data collection and processing and two anonymous reviewers for their comments on an earlier version of our manuscript.
Copyright 2014 Elsevier B.V., All rights reserved.
- Betula alleghaniensis
- Gap-partitioning theory
- Kernel density estimate (KDE)
- Northern hardwoods
- Ripley's K
- Tsuga canadensis