Paper documents “green tree retention” patterns in loblolly pine forests

When even-aged forests are harvested, managers sometimes retain features such as snags and living green trees to enhance stand-level structural and biological diversity.

In the southeastern Coastal Plain, green trees are most often retained within streamside management zones (SMZs) along perennial and intermittent streams, and within narrower “stringers” along ephemeral drains; however, scattered live trees and/or patches of unharvested vegetation may also be retained, particularly in wet areas.

Retaining unharvested vegetation in association with SMZs and stringers and in other patches allows managers to protect water quality and reduce interference with regeneration and other silvicultural treatments in harvested areas while also enhancing structural diversity.

For several years, NCASI has been collaborating with Mississippi State University to characterize the vegetation structure of SMZs and stringers associated with new established (three years post-establishment), intensively managed pine forest stands in the South Central Plains ecoregion of Arkansas and Louisiana. The investigators also documented bird communities on a subset of these same study sites.

The most recent paper from this study was recently made available online by the journal Forest Science. The authors, who include Michael C Parrish, Steve Demarais, Sam K Riffell, Andrew W Ezell, and Phillip D Jones of Mississippi State University and T Bently Wigley of NCASI, document operational green tree retention practices in the region. Based on an analysis of more than 1,100 regenerating loblolly pine stands and associated unharvested vegetation, they found that retained vegetation represented >18% of the area in these “management units.”

The abstract for the paper follows.

Southern US landowners participating in forest certification programs sometimes use green tree retention in intensively managed pine (Pinus spp.) forests (IMPF) to promote structural diversity and to benefit wildlife species. However, the operational extent of green tree retention practices is poorly understood. Therefore, we classified land cover on 1187 South Central Plains IMPF management units (“MUs”; totaling 51245.7 ha), defined as contiguous, forested areas containing one or more IMPF patches, harvested and established as a cohort, plus associated green tree retention areas. For each MU, we calculated green tree retention levels and generated land cover pattern metrics describing MU composition and configuration. As expected given our sampling frame, MU land cover was dominated by regenerating clearcut (mean ± sd: 80.5% ± 14.3% of land cover) and green tree retention cover (mean 18.6% ± 14.2% of land cover). Retention cover consisted mostly of streamside management zones (mean 14.0 % ± 13.1% of land cover) buffering perennial and intermittent streams and stringers (mean 3.4% ± 4.3% of land cover) buffering ephemeral streams. Green tree retention land cover represented a substantial proportion of the IMPF landscape in the region and potentially enhances habitat conditions for many wildlife species.

Reference

Michael C Parrish, M.C., S. Demarais, T.B. Wigley, S.K. Riffell, A.W. Ezell, and P.D. Jones. 2018. Operational green tree retention and land cover patterns in intensively managed pine forest landscapes of the southeastern United States. Forest Science, fxy009, https://doi.org/10.1093/forsci/fxy009