Publications address “green tree retention” in intensively managed loblolly pine forests of Arkansas and Louisiana

When even-aged forests are harvested, forest managers sometimes retain features such as snags and living green trees to enhance stand-level structural and biological diversity. Unharvested trees and snags are retained within harvest units as scattered individual stems, aggregated groups of stems, or as larger patches. 

In the South, intensively managed pine forests are commonly harvested using clearcutting, and green trees are retained within streamside management zones (SMZs) along perennial and intermittent streams, and within narrower “stringers” along ephemeral drains. Retaining unharvested vegetation along riparian corridors 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 60 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 these same study sites. Two recent publications in Forest Ecology and Management presented results from this study.

One paper (Parrish et al. 2017a) describes and contrasts the patch-scale forest structural characteristics of the SMZs and stringers. The authors found that snag and log density, midstory pine density, understory deciduous cover, and ground cover were not statistically different in stringers and SMZs. However, overstory (pine and deciduous) and midstory (deciduous) tree density was significantly lower in stringers than in SMZs, and understory pine density was significantly greater in stringers. Thus, the authors concluded that the vegetation structure provided by stringers complements that of SMZs and the regenerating portion of the intensively managed pine stands, potentially increasing the value to biodiversity of the latter two cover types.

In the second paper, Parrish et al. (2017b) describe breeding season bird communities on these same 60 sites. There was an 84% bird species overlap between SMZs and stringers. Thus, stringers augmented SMZ contributions to site avian diversity by hosting bird species associated with older forests. In addition, diversity of birds typically associated with young forests was similar between stringers and the regenerating portion of these pine stands. The authors concluded that retention of SMZs and stringers contributed to stand scale bird diversity, and that stringers in particular appeared to enhance the value to bird species diversity of both SMZs and the regenerating portion of the stands.

References 

Parrish, M.C., S. Demarais, A.W. Ezell, T.B. Wigley, P.D. Jones, and S.K. Riffell. 2017a. Retained vegetation density of streamside management zones and stringers in southern intensively managed pine forests. Forest Ecology and Management 397:89–96. https://doi.org/10.1016/j.foreco.2017.04.024 

Parrish, M.C., S. Demarais, T.B. Wigley, P.D. Jones, A.W. Ezell, and S.K. Riffell. 2017b. Breeding bird communities associated with land cover in intensively managed pine forests of the southeastern U.S. Forest Ecology and Management 406:112–124. https://doi.org/10.1016/j.foreco.2017.09.063