@article{dunn_unruh snyder_mccarter_frey_idassi_schnake_cubbage_2021, title={Bioeconomic Assessment of an Alley Cropping Field Trial in North Carolina, U.S.: Tree Density, Timber Production, and Forage Relationships}, volume={13}, ISSN={2071-1050}, url={http://dx.doi.org/10.3390/su132011465}, DOI={10.3390/su132011465}, abstractNote={Silvopasture, the combination of trees, forage, and livestock, is a management practice that is gaining interest throughout the southeastern U.S. This research analyzed a hay-based alley cropping field trial that is transitioning into a silvopasture system. We planted four different tree spacings—2.4 × 2.4 m, 2.4 × 3.0 m, 3.0 × 3.0 m, and 1.8 × 3.0 m (8 × 8 ft, 8 × 10 ft, 10 × 10 ft, and 6 × 10 ft)—of loblolly pine (Pinus taeda L.) and used secondary data for the possible planting of two different grass species—big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.). Tree inventories, forage samples, biometric modeling, and economic analysis of forage and timber monocultures and mixed systems were analyzed with discounted cash flow and capital budgeting analyses. Tree growth on the pasture site was exceptionally fast, generating high projected returns for timber monocultures, which exceeded returns for monoculture grass crops. Projected timber stand returns had the greatest Net Present Values (NPV) at the 4% discount rate, ranging between USD 3196 and USD 3552 per ha (USD 1294 and USD 1438 per ac) for a 2.4 × 3.0 m or 2.4 × 2.4 m tree spacing yield. Representative grass yields were obtained from secondary sources and had lower productivity, with switchgrass having the highest returns at USD 2581 per ha (USD 1045 per ac). Optimal NPVs for mixed silvopasture stands ranged between about USD 1500 per ha and USD 3500 per ha (USD 600/ac and USD 1400/ac), depending on the tree spacing within bands, the alley spacing, and the degree of competition between trees and grasses.}, number={20}, journal={Sustainability}, publisher={MDPI AG}, author={Dunn, Kenneth and Unruh Snyder, Lori and McCarter, James and Frey, Gregory and Idassi, Joshua and Schnake, David and Cubbage, Frederick}, year={2021}, month={Oct}, pages={11465} }
 @article{willis_schnake_deperno_lashley_wetzstein_yow_2021, title={Tree encroachment impacts on seed predator selection and seedling establishment in degraded pine woodlands}, volume={24}, ISSN={1402-2001 1654-109X}, url={http://dx.doi.org/10.1111/avsc.12570}, DOI={10.1111/avsc.12570}, abstractNote={AbstractQuestionsWhile much is known about the impact of tree encroachment on flammability in degraded pine woodlands, little is known about how encroachment is impacting other important ecosystem functions. We investigated how the availability of seed from four encroaching tree species and the presence of a midstorey and litter layer affect seed predator selection. Additionally, we investigated how seed predators, the midstorey, overstorey basal area, substrate availability, and vegetation cover affect germination for a foundational species (Pinus palustris) compared to an encroaching species (Pinus taeda).LocationSandhills Ecoregion, NC, USA (35°3′34.6932″ N, 79°22′22.0872″ W).MethodsWe measured seed depredation of Pinus palustris, Pinus taeda, Liquidambar styraciflua, Acer rubrum, and Quercus nigra in cafeteria trials. Each trial was held within a 2 × 2 factorial involving vertebrate seed predator exclusion and midstorey and litter layer removal across a gradient of overstorey basal area (6–25 m2). Additionally, we measured Pinus palustris and Pinus taeda germination within each treatment and correlated germinant density to substrate and understorey vegetation cover.ResultsGranivory generally varied inversely with seed size, with small‐seeded Liquidambar styraciflua experiencing the highest (27%) and large‐seeded Quercus nigra (7%) and Acer rubrum (6%) the lowest depredation pressure. Pinus palustris and Pinus taeda germinant density was significantly highest where vertebrate seed predators were excluded and the midstorey and litter layer were removed. For both pine species, this result corresponded with a significant positive association with mineral soil and negative associations with hardwood and pine litter where vertebrate predators were excluded. Basal area did not affect granivory or germination for any species.ConclusionsOur results demonstrate that granivores did not select Pinus palustris, and that large‐seeded species encroachment was less inhibited by seed predators. Pinus palustris and Pinus taeda are depredated at comparable rates and germinate best under similar understorey conditions.}, number={1}, journal={Applied Vegetation Science}, publisher={Wiley}, author={Willis, John L. and Schnake, David K. and DePerno, Christopher S. and Lashley, Marcus A. and Wetzstein, Branson and Yow, Justin}, editor={Acosta, Alicia Teresa RosarioEditor}, year={2021}, month={Jan} }