Vegetative diversity and composition correlates with avifaunal diversity and composition in pine forests of the Atlantic coastal plain

Background/Question/Methods

Efforts aimed at restoring terrestrial ecosystems to pre-settlement conditions emphasize the recovery of both structural and compositional characteristics. Among the fire-suppressed pine forests of the Atlantic coastal plain, a recovery of structural characteristics often requires the removal of a hardwood mid-story that has accumulated as a result of fire suppression or exclusion. Such a procedure enhances the structural similarities between the treated forest and fire-maintained pine savannas and stimulates the growth of the forest herbaceous layer. However, such a procedure does not result in an immediate recovery of endemic herbaceous species composition, and the degree to which organisms on higher trophic levels prefer or rely upon communities that are characteristic of pre-settlement conditions remains poorly understood. Here, we examine the role of herbaceous community composition on the avifaunal community composition in fire-maintained longleaf pine savannas as well as fire-suppressed loblolly pine forests. We conducted censuses of both plant and avifaunal communities in 46 mature (50-70 years old) pine stands in the North Carolina coastal plain to examine of the roles of both forest structure and understory species composition in determining avifaunal habitat selection. Of the 46 plant-avifaunal monitoring sites (PAMS) in our study area, 22 were fire-maintained longleaf pine savannas and 24 were loblolly pine forests of varying degrees of mid-story accumulation. Variations in plant and avifaunal species composition among the plots were evaluated using nonmetric multidimensional scaling (NMS) analysis.  

Results/Conclusions

Results from the NMS ordination demonstrate that even though our study sites were comprised entirely of mature pine stands, both plant and avifaunal communities showed patterns of differentiation that were similar for both groups, producing significant overlap in ordination space. Such an overlap suggests that the composition of avifaunal communities is tightly correlated to the differences vegetative composition that can emerge in mature pine stands, indicating that avifaunal community composition is tightly linked to the composition of herbaceous plant communities. Additionally, we found a linear relationship between plant species richness and avifaunal species richness (p<0.0001), giving further suggestion to the important role of the herbaceous layer in determining avifaunal community composition among pine forests of comparable age and structure.