In the southern United States, institutional forest owners engaged in forest certification programs often retain unharvested or less-intensively harvested vegetation when clearcut harvesting intensively managed pine (Pinus spp.) forests (“IMPFs”), a practice called ‘green tree retention’. I investigated resultant patterns of land cover and retained structural elements in recently-harvested IMPF management units (“MUs”) and related them to avian biodiversity to provide information to support harvest decisions. First, to provide forest managers baseline data on retention, I screen-digitized land cover on 1187 MUs (totaling 51646 ha) and characterized green tree retention levels and internal land cover attributes (Chapter 2). I found MU land cover was dominated by regenerating clearcuts (mean: 80.5%), streamside management zones (“SMZs”; vegetated buffers surrounding intermittent and perennial streams; 14.0%) and stringers (buffers surrounding ephemeral streams; 3.3%). Next, I surveyed 60 MUs for vegetation stem density and cover (Chapter 3). Concurrently, I surveyed avian community density and richness (Chapter 4). Vegetation and avian metrics were compared and contrasted across the dominant cover types (with emphasis on stringer/SMZ similarity) to understand impacts of retained structural elements on biodiversity outcomes. I found that snag and log density, midstory pine density, understory deciduous cover, and ground cover were not different in stringers and SMZs; however, overstory (pine and deciduous) and midstory (deciduous) tree density was lower in stringers than in SMZs, and understory pine density was greater in SMZs. Species overlap between cover types was high (74% to 84%), but SMZs and stringers provided 27% of MU species richness. Stringers appeared to benefit both shrubland- and forest-associated birds. Finally, I sampled land cover across 4450 sq-km surrounding the 60 MUs, and performed ordination analyses to identify associations between local-scale (MU interiors) and landscape-scale (3-km buffers around MUs) land cover and avian guild diversity (Chapter 5). I found the region to be >90% forested. Cover type data explained 41% of the partial variation in avian density and total species richness. Local-scale MU characteristics appeared more important than landscape-scale characteristics in explaining avian biodiversity responses. My results suggest that retained structural features support and enhance MU biodiversity in harvested IMPFs.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-2749 |
| Date | 14 December 2018 |
| Creators | Parrish, Michael Clay |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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