Complex Planting Patterns for Increasing the Structural Diversity of Shortleaf Pine Restoration Plantings

Structural complexity in natural ecosystems is vital for a variety of ecological benefits, ranging from carbon storage to enhanced wildlife habitat. Artificially regenerated pine plantations established for timber production and restoration of species such as shortleaf pine typically exhibit low levels of complexity. Due to the benefits of structural complexity, it can be hypothesized that implementation of more complex planting patterns in plantations established during restoration efforts may provide additional ecological benefits while maintaining the production of forest products and other important ecosystem services provided by pine plantations. The overarching objective of this research was to determine if the development of complex structure can be expedited within an artificially regenerated shortleaf pine stand by using complex planting patterns. Specific objectives were to: 1) Document any differences in the variability of understory vegetation horizonal and vertical structure between the complex planting pattern treatment and control; 2) Analyze differences in the richness of understory vegetation between the treatment and control; 3) Establish any differences in the variability of soil temperature and photosynthetically active radiation between the treatment and control; and 4) Analyze differences in planted shortleaf pine performance between the treatment and control, and also across different understory patch types. Results for the first growing season did not definitively support significant effects of the complex planting treatment on structural complexity, plant richness, microclimate factors, and shortleaf pine performance. The lack of strong treatment effects can likely be attributed to the limitations of baseline data collected during the first growing season of the shortleaf pine seedlings. Pre-burn patterns in the distribution of slash and understory plants and fire behavior during the burns conducted just prior to planting may have had much stronger effects on the variables measured than the complex planting treatment. Further data collection in subsequent years may provide more conclusive results regarding the effects of complex planting patterns on elements of structural complexity and shortleaf pine performance. Additional investigations of prescribed fire behavior and wildlife use will also be possible with continued development of the vegetation and soils on the study sites.