Site Preparation for Longleaf Pine Restoration on Hydric Sites: Stand Development and Ground Layer Responses 15 Years Following Planting

Dr. Benjamin Knapp | University of Missouri



The restoration and management of longleaf pine ecosystems are of high priority for land managers throughout the southeastern United States, including several large Department of Defense (DoD) installations. The overall goal of this project is to determine the effects of site preparation treatments on the development of longleaf pine (Pinus palustris) plantations at a temporal scale appropriate for evaluating restoration outcomes and informing management decisions on wet Coastal Plain sites. This project will re-measure study plots established for SERDP Project RC-1303, “Regenerating Longleaf Pine on Hydric Soils: Short- and Long-term Effects on Native Ground-layer Vegetation,” which provided information about site preparation treatment effects through three years following artificial regeneration. However, it will likely take years or decades to reach restoration targets, and initial measured responses may or may not persist through stand development.

The specific objectives of this project are to: O1) determine the effects of site preparation treatments on the establishment of longleaf pine stands (e.g., tree survival, emergence from the grass stage, and tree size) 15 years after plantation establishment; and O2) determine the effects of site preparation treatments on ground layer and mid-story vegetation abundance, species richness, and composition 15 years after plantation establishment.

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Technical Approach

Researchers will resample the field experiment established in 2003 for RC-1303. Study treatments included eight combinations of site preparation treatments: F (flat planting; control), HF (herbicide and flat-planting), CF (chopping and flat-planting), HM (herbicide and mounding), CM (chopping and mounding), HB (herbicide and bedding), CB (chopping and bedding), and CHB (chopping, herbicide, and bedding). Planted longleaf pine seedlings and ground layer vegetation responses were previously measured through the first three growing seasons following treatment. Researchers will follow sampling protocol similar to that from RC-1303 for response variables previously measured, including the number of trees per hectare (survival), height of longleaf pines, and the abundance, richness, and composition of ground layer vegetation. In addition, researchers will measure several response variables for longleaf pine trees that were not applicable for grass stage seedlings in the previous measurements, including diameter at breast height and stand basal area. Researchers will destructively sample a random sample of longleaf pine trees from each experimental unit to determine patterns in height growth through time and describe local variation in ground layer abundance in relation to bedding treatment and plantation canopy closure.

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This study will fill a knowledge gap regarding the development of longleaf pine plantations on wet, Coastal Plain sites. Currently, it is not known if site preparation treatments are required on this site type for successful establishment of planted seedlings or if site preparation treatments have long-term, negative impacts on ground layer vegetation. This study will provide opportunity for confirmation of results from RC-1303 regarding early effects of site preparation treatments on longleaf pine seedlings and ground flora. Moreover, this study will provide actionable information for management decisions about longleaf pine restoration on these site types. Results from this study will improve the basic understanding of longleaf pine plantation development by reconstructing height growth patterns of longleaf pine saplings to evaluate if site preparation treatments result in sustained positive impacts on tree growth through time or if differences among observed tree heights are a function of time since emergence from the grass stage.

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Points of Contact

Principal Investigator

Dr. Benjamin Knapp

University of Missouri

Phone: 573-882-0867

Program Manager

Resource Conservation and Resiliency