Geology topics

Samuel K. Riffell

Publications and source records attributed to Samuel K. Riffell.

5 recordsLinked to original sources

USGS2017

Nest survival modelling using a multi-species approach in forests managed for timber and biofuel feedstock

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 km 2 ), although at a local scale (50 m 2 ) switchgrass negatively influenced nest survival. A likely explanation is intercropping shifted community composition, favouring species with greater disturbance tolerance.

Journal of Applied Ecology↗

USGS2014

Avian response to conservation buffers in agricultural landscapes during winter

Native herbaceous vegetation cover along row‐crop field edges (i.e., field buffers) increases breeding densities of many bird species. However, the effect of field buffers on bird species during the non‐breeding season is less understood. We compared density, avian richness, and avian conservation value on row‐crop fields containing buffers strategically designed for wildlife versus fields without buffers in 3 southeastern U.S. states during winter 2007 and 2008. Fields with buffers were enrolled in U.S. Department of Agriculture, Conservation Reserve Program practice Habitat Buffers for Upland Birds (CP33), which targets restoration of northern bobwhite ( Colinus virginianus ) and other upland bird species. Overall species richness did not differ on fields with buffers versus fields without buffers in 2007, but was 29% greater on fields with buffers in 2008. Swamp sparrows ( Melospiza georgiana ), song sparrows ( M. melodia ), field sparrows ( Spizella pusilla ), and red‐bellied woodpeckers ( Melanerpes carolinus ) had greater densities on fields with buffers compared with fields without buffers. Increasing field‐buffer width did not result in greater bird densities. Our results suggest a small change in primary land use (≈7%) produced a disproportionate population response by some grassland‐dependent and woodland bird species during winter. Because field buffers provide a direct source of winter food and cover resources, they may be a pragmatic means to provide critical non‐breeding habitat with little alteration of existing agricultural systems.

Arkansas, Kentucky, Mississippi↗

USGS2014

Breeding bird community response to establishing intercropped switchgrass in intensively-managed pine stands

Intercropping switchgrass ( Panicum virgatum L.) between tree rows within young pine ( Pinus spp.) plantations is a potential method to generate lignocellulosic biofuel feedstocks within intensively managed forests. Intensively managed pine supports a diverse avian assemblage potentially affected by establishment and maintenance of an annual biomass feedstock via changes in plant communities, dead wood resources, and habitat structure. We sought to understand how establishing switchgrass on an operational scale affects bird communities within intercropped plantations as compared to typical intensively managed loblolly pine ( Pinus taeda L.) forest. We conducted breeding bird point counts using distance sampling for three years (2011–2013) following establishment of intercropped switchgrass stands (6 replicates), traditionally-managed pine plantations, and switchgrass-only plots (0.1 km 2 minimum) in Kemper Co., MS. We detected 59 breeding bird species from 11,195 detections. Neotropical migrants and forest-edge associated species were less abundant in intercropped plots than controls the first two years after establishment and more abundant in year three. Short distance migrants and residents were scarce in intercropped and control plots initially, and did not differ between these two treatments in any year. Species associated with pine-grass habitat structure were less abundant initially in intercropped plots, but converged with pine controls in subsequent years. Switchgrass monocultures provided minimal resources for birds. If songbird conservation is a management priority, managers should consider potential reductions of some breeding birds for one to two years following intercropping. It is unclear how these relationships may change outside the breeding season and as stands age.

Biomass and Bioenergy↗

USGS2013

Site preparation for switchgrass intercropping in loblolly pine plantations reduces retained trees and snags, but maintains downed woody debris

Within young pine ( Pinus spp.) plantations, coarse woody debris (CWD) and green trees are important habitat structures that may be impacted by the production of biofuel feedstock. Therefore, we compared site preparation procedures associated with switchgrass ( Panicum virgatum L.) intercropping to determine effects on CWD and green trees in stands ( n = 24) site-prepared for intercropping, with switchgrass only, or pine plantation in Mississippi, USA. Following site preparation, CWD dispersal or volume did not differ between intercropped and control stands. Intercropped stands had significantly fewer retained trees and snags. Switchgrass monocultures had no retained trees or piles and significantly fewer pieces and less volume of CWD than the other treatments. Our results suggest switchgrass intercropping may provide similar habitat quality to traditional pine plantations for wildlife species using these areas in the year following disturbance, but may provide a less suitable habitat for species that require snags. However, the relationship between snag reduction and wildlife population response in an intercropped setting is not clear and should be further investigated. Regardless, if retaining snags is a desired outcome, site preparation for switchgrass should be restricted to the interbed area where it will be cultivated as opposed to extensive debris removal from the entire site.

Mississippi↗

USGS2012

Provisioning of nestling Dickcissels in native warm-season grass field buffers

We used video cameras in 2008–2009 to record provisioning activities at Dickcissel (Spiza americana) nests in and around Conservation Reserve Program field buffers in north-central Mississippi, USA. We simultaneously observed foraging flight distances of parents. Provisioning rate (P = 0.412), biomass (P = 0.161), and foraging distance (P = 0.159) did not increase with nestling age. Parents delivered larger items to meet demand associated with older nestlings (P = 0.010–0.001). This suggests energetic costs of changes in prey selection were less than costs of increasing the number or distance of provisioning trips. Presence of male helpers increased provisioning rate (P < 0.001) but not biomass (P = 0.992) because males brought smaller prey items (P = 0.001–0.021). Presence of observers 30 m from the nest reduced provisioning rates (P = 0.005) and biomass delivered (P = 0.066). Lack of habitat effects for any aspect of provisioning suggests grass field buffers provided nestling food resources similar to surrounding habitats. Use of continuous video monitoring of nest activity allows well-concealed activities including provisioning and male helping to be directly observed and better quantified.

Mississippi↗