A preliminary analysis of the response of an avian community to silvicultural treatments in the southern Cumberland Plateau, Alabama, USA

Abstract

We simulated a shelterwood forest regeneration treatment by reducing basal area, and monitored the response of an avian community in oak-hickory forest on the southern Cumberland Plateau, northern Alabama, USA. We used five treatments: control (no removal), clear-cut (100% removal), and 25, 50, and 75% removal of basal area. Territory mapping was used to quantify bird community between mid-April and July of both 2002 and 2003. Microclimate variables were recorded at each plot. The residual basal area and canopy cover showed three distinct conditions after treatment: closed canopy, open forest, and clear-cut. The microclimate varied among treatments: air temperature was highest in clear-cut plots and lowest in control plots, whereas soil moisture had the opposite pattern. A total of 71 bird species were detected, with 36 of them defending territories. Territory density, species richness, and Shannon diversity index differed among the treatments; the relationship between these bird community indices and the level of basal area removal was quadratic, lowest in the clear-cut plots and highest in the intermediate levels. Although species richness was similar among the control, 25, 50, and 75% removal treatments, species composition varied. The richness difference among treatments became smaller in the second year post-treatment (2003) with an increase in bird density and richness occurring in the clear-cut plots.

Effects of patch size and basal area on avian taxonomic and functional diversity in pine forests: Implication for the influence of habitat quality on the species–area relationship

“…Wang et al. () reported that in oak–hickory forest, Red‐eyed Vireo ( Vireo olivaceus ; forest interior) was most abundant at closed canopy (control and 25% basal area removal plots), whereas Indigo Bunting ( Passerina cyanea ; classified as early successional species in their study) was most abundant at open canopy (≥50% basal area removal plots). Some early successional species such as Blue Grosbeak ( Passerina caerulea ) and Prairie Warbler ( Setophaga discolor ) were observed only at open canopy sites.…”

“…Wang et al. () also found the highest territory density and species richness at intermediate open canopy (50% and 75% basal area removal plots, respectively). Wang et al.…”

“…Wang et al. () did not clearly describe the levels of basal area. The range of basal area used to define basal area classes in their study could be different from ours.…”

“…For instance, Canterbury et al (2000) found that the richness of shrubland species was strongly negatively correlated with tree basal area. Wang et al (2006) (Garrison, 1986;Kerpez & Stauffer, 1989). In our study, those early successional or shrubland species were pine-grassland species.…”

“…Conversely, too low basal area of a patch (e.g., heavy thinning) can have a negative impact on tree nesting species and mature forest or forest interior species that prefer relatively dense canopy cover. These negative or positive effects of basal area on diversity and occurrence of avian species are often observed in hardwood forests or mixed pine-hardwood forests (Canterbury, Martin, Petit, Petit, & Bradford, 2000;McDermott & Wood, 2011;Wang, Lesak, Felix, & Chweitzer, 2006). Although several studies have been conducted to determine the effects of basal area on avian species in other ecoregions (Wilson, Masters, & Bukenhofer, 1995;Wood, Burger, Bowman, & Hardy, 2004), little is known about how basal area influences avian diversity in the Sandhills Ecoregion.…”