Breeding, Early-Successional Bird Response to Forest Harvests for Bioenergy

Abstract

Forest regeneration following timber harvest is a principal source of habitat for early-successional birds and characterized by influxes of early-successional vegetation and residual downed woody material. Early-successional birds may use harvest residues for communication, cover, foraging, and nesting. Yet, increased market viability of woody biomass as bioenergy feedstock may intensify harvest residue removal. Our objectives were to: 1) evaluate effects of varying intensities of woody biomass harvest on the early-successional bird community; and (2) document early-successional bird use of harvest residues in regenerating stands. We spot-mapped birds from 15 April– 15 July, 2012–2014, in six woody biomass removal treatments within regenerating stands in North Carolina (n = 4) and Georgia (n = 4), USA. Treatments included clearcut harvest followed by: (1) traditional woody biomass harvest with no specific retention target; (2) 15% retention with harvest residues dispersed; (3) 15% retention with harvest residues clustered; (4) 30% retention with harvest residues dispersed; (5) 30% retention with harvest residues clustered; and (6) no woody biomass harvest (i.e., reference site). We tested for treatment-level effects on breeding bird species diversity and richness, early-successional focal species territory density (combined and individual species), counts of breeding birds detected near, in, or on branches of harvest piles/windrows, counts of breeding bird behaviors, and vegetation composition and structure. Pooled across three breeding seasons, we delineated 536 and 654 territories and detected 2,489 and 4,204 birds in the North Carolina and Georgia treatments, respectively. Woody biomass harvest had limited or short-lived effects on the early-successional, breeding bird community. The successional trajectory of vegetation structure, rather than availability of harvest residues, primarily drove avian use of regenerating stands. However, many breeding bird species used downed wood in addition to vegetation, indicating that harvest residues initially may provide food and cover resources for early-successional birds in regenerating stands prior to vegetation regrowth.

Alternative biomass strategies for bioenergy: implications for bird communities across the southeastern United States

“…Interpreting the potential effects of an expansion in biofuel and bioenergy production on biodiversity requires systematic comparisons regarding potential alternative biomass strategies being considered. To date, most comparisons on the biodiversity within bioenergy crops compare these stands to native, natural habitats or only consider single harvest methods (Fritts et al ., ; Grodsky et al ., ). While such comparisons are useful, these comparisons do not allow a formal assessment of relative impacts to biodiversity of biomass alternatives being considered across regions.…”

“…As hypothesized, the harvest of logging residues from clear‐cut plantations had consistently negative effect on avian occupancy across all nesting and foraging guilds in the study, but the magnitude of the effect was surprising. In addition, a recent experiment on residue removal found little effects on breeding and wintering birds (Grodsky et al ., ,b); rather, Grodsky et al . (,b) and instead suggested that the successional trajectory of vegetation (e.g., sapling growth/tree successional stage) was more critical than residue retention per se.…”

“…In addition, a recent experiment on residue removal found little effects on breeding and wintering birds (Grodsky et al ., ,b); rather, Grodsky et al . (,b) and instead suggested that the successional trajectory of vegetation (e.g., sapling growth/tree successional stage) was more critical than residue retention per se. Similarly, the understory of clear‐cuts where debris was retained varied substantially in our study area, and some had a well‐developed understory and vertical structure (e.g., snags and nontarget trees), which was reflected by variation in basal area and DBH of remaining trees (Table ).…”

Legacy forest structure increases bird diversity and abundance in aging young forests

“…Multiple studies have examined the responses of bird functional guilds to harvest and time since harvest (Duguid et al, ; Newell & Rodewald, ; Preston & Harestad, ; Tozer, Burke, Nol, & Elliott, ). Previous studies of the effects of variable retention harvests have suggested that the successional trajectory of the forest drives bird community composition and that bird species richness and abundance decline in stem exclusion (Duguid et al, ; Grodsky, Moorman, Fritts, Castleberry, & Wigley, ; Winkler, ). As reported in other studies, our results show that bird abundance within the shrub‐nesting functional guild decreases swiftly as the stand regenerates postharvest.…”

Impact of increased wood pellet demand on biodiversity in the south‐eastern United States

“…Unfortunately, we were unable to include the impacts of intensification of existing management plantations in our analysis, because projections of intensification of existing plantations for the study region were not available, and the GAP habitat suitability models do not distinguish between different management intensities in pine plantations. Forest management can have either positive effects, for instance due to thinning (Gottlieb et al, ; Verschuyl et al, ), or neutral or negative impacts, for instance due to residue removal (Fritts et al, ; Gottlieb et al, ; Grodsky, Moorman, Fritts, Castleberry, & Wigley, ; Grodsky, Moorman, Fritts, & Hazel, et al, ; Riffell et al, ) on species richness. Therefore, impacts on species richness due to pine plantation establishment may be overestimated if new plantations are not managed intensively.…”