No abstract

Switchgrass (Panicum virgatum) intercropping is a novel forest management practice for biomass production intended to generate cellulosic feedstocks within intensively managed loblolly pine‐dominated landscapes. These pine plantations are important for early‐successional bird species, as short rotation times continually maintain early‐successional habitat. We tested the efficacy of using community models compared to individual surrogate species models in understanding influences on nest survival. We analysed nest data to test for differences in habitat use for 14 bird species in plots managed for switchgrass intercropping and controls within loblolly pine (Pinus taeda) plantations in Mississippi, USA. We adapted hierarchical models using hyper‐parameters to incorporate information from both common and rare species to understand community‐level nest survival. This approach incorporates rare species that are often discarded due to low sample sizes, but can inform community‐level demographic parameter estimates. We illustrate use of this approach in generating both species‐level and community‐wide estimates of daily survival rates for songbird nests. We were able to include rare species with low sample size (minimum n = 5) to inform a hyper‐prior, allowing us to estimate effects of covariates on daily survival at the community level, then compare this with a single‐species approach using surrogate species. Using single‐species models, we were unable to generate estimates below a sample size of 21 nests per species. Community model species‐level survival and parameter estimates were similar to those generated by five single‐species models, with improved precision in community model parameters. Covariates of nest placement indicated that switchgrass at the nest site (<4 m) reduced daily nest survival, although intercropping at the forest stand level increased daily nest survival. Synthesis and applications. Community models represent a viable method for estimating community nest survival rates and effects of covariates while incorporating limited data for rarely detected species. Intercropping switchgrass in loblolly pine plantations slightly increased daily nest survival at the research plot scale (0.1 km2), although at a local scale (50 m2) switchgrass negatively influenced nest survival. A likely explanation is intercropping shifted community composition, favouring species with greater disturbance tolerance.

Switchgrass (Panicum virgatum) is a cellulosic feedstock for alternative energy production that can be grown between rows of planted pines (Pinus spp.) within intensively managed forests. Southeastern planted pine occupies 15.8 million ha and thus, switchgrass intercropping could have far‐ranging effects on plant communities and biomass production within these forests if broadly implemented. Such intercropping could lead to alterations to plant communities that may cause bottom‐up ecological changes affecting ecologically, economically, and socially important wildlife, such as white‐tailed deer (Odocoileus virginianus; deer). Therefore, we tested whether intercropping switchgrass in loblolly pine (P. taeda) plantations would cause switchgrass to dominate vegetative biomass thereby decreasing biomass of forages and reducing white‐tailed deer nutritional carrying capacity (NCC), or whether disturbance associated with establishment and harvest of switchgrass would facilitate ruderal forbs, and thereby increase biomass of preferred deer forages and increase NCC. In a randomized complete block design, we assigned 2 treatments (intercropped switchgrass and a standard pine management control) to 4 replicates of 10‐ha experimental units in Kemper County, Mississippi during summers of 2011−2015. We detected 323 plant species. Intercropping switchgrass had little effect on plant biomass production, and did not affect white‐tailed deer NCC at a maintenance diet of 6% crude protein. Intercropping provided additional disturbance allowing high‐protein content ruderal plants to colonize, and temporarily increased (3 yr) deer NCC at the 14% crude protein diet considered necessary to support lactation. However, concomitant with a sharp increase in switchgrass biomass in the third year of the study, NCC dropped to levels similar to traditionally managed pine stands. Switchgrass intercropping is not a reliable means of increasing deer NCC as a management strategy but does not appear to reduce carrying capacity in the short‐term relative to standard intensive pine management. © 2017 The Wildlife Society.