1. Conclusion & Discussion
Avian Use of a Bottomland Hardwood Afforestation Site in the Red River Alluvial Valley Colby W. Sharp1 and Heidi L. Adams2 1School of Biological Sciences, Louisiana Tech University; 2School of Agricultural Sciences and Forestry, Louisiana Tech University
Abstract
Bottomland hardwood forests cover about 2.8 hectares of the original 10 million hectares that once existed in the southeastern United States. These losses have led to an emphasis on afforestation of retired agricultural land. It is important evaluate changes in wildlife communities as these afforested stands mature. For instance, topographic variation within them can lead to certain tree species becoming better established in certain areas compared to others, leading to an afforested stand with forest types of differing species. Previous research at an 809-ha afforested bottomland hardwood stand near Coushatta, Louisiana identified seven forest types. We conducted point count surveys at 28 point locations evenly distributed among the forest types at the afforested stand six times during the avian breeding (i.e., June-August, twice/month), recording detected species and its distance from point. We used DISTANCE 7.0 to estimate detection function and avian density within each forest types. Avian diversity was calculated for each forest type using Shannon's Diversity Index. Preliminary results for bird density in each forest types ranged from bird/ha in willow oak (Quercus phellos) to birds/ha in sweet pecan (Carya illinoinensis). Shannon’s Diversity Indices for 2016 diversity analysis ranged from (H max = 2.565) in sweetgum (Liquidambar styraciflua) to (H max = 2.833) in sweet pecan, with diversity analysis in 2017 showing changes with sweet pecan increasing by and sugarberry persimmon at Results of study will aid in developing forest management recommendations to promote breeding bird use of the afforested stand
Study Site and Methods
The study site is an 809-ha afforested bottomland hardwood stand near Coushatta, LA that is owned by NRG Energy, Inc (Fig. 1). It was planted with bottomland hardwoods during the winters of and by US Fish and Wildlife Service. We conducted point count surveys at 28 randomly selected point that were evenly distributed among the study site’s 7 forest types,previously identified by Strozier (2015), 6 times during the avian breeding (i.e., June-August 2016 and 2017, twice/month). We recorded species and distance from the observer for all individual birds detected. We used DISTANCE 7.0 to estimate avian density within each of the forest types and compared them using the 95% confidence intervals. Avian diversity was calculated for each forest types using Shannon's Diversity Index (H’) and Equitability (J’).
Figure 4. A yellow-breasted chat fledgling detected during point counts at the afforested bottomland hardwood study site.
Conclusion & Discussion
Based on preliminary results, our data indicates that density of breeding birds at our study site vary with forest type, but it is evident that a year effect could be present due to the 2017 avian densities being more similar than 2016 avian densities. For instance in 2016 sweet pecan and sweetgum (similarity group a) have a higher density than willow oak (group c). From these results we could infer that bird species are less attracted to the willow oak forest type. These difference seem to be less prevalent in 2017 avian density, shown by the lack of distinct groupings (due to overlapping error bars).Weather patterns could allow for better breeding conditions in some forest types, thus showing this change. Diversity and equitability appear to be similar across forest types for both the 2016 and 2017 breeding season. However, with respect to both density and diversity estimates further data collection is require in order to account for variation among these variable from year to year. We plan to conduct 1 more data collection during 2018 breeding seasons.
In future data collection seasons we will conduct vegetative sampling to determine vegetation density and diversity within each of the forest types. This is important because understory vegetation can add additional cover and food sources for woodland birds. After the 2018 breeding season, we will compare our bird diversity to avian species characteristic of mature bottomland hardwood stands in the southeastern United States. This species list will be based on a review from published literature. Species in mature bottomland hardwood stand and 25 year old bottomland hardwood stand should be 75 to 85% similar if the 25 year old stand is going to be optimal habitat for woodland birds (Nuttle and Burger 2005). Results form this study will aid in the creation of assessment techniques for afforested bottomland hardwood to be used in the future, and determining if forest management recommendations are necessary.
Results
We detected 297 bird observations representing 34 different species during point counts during the 2016 breeding season. Species that we most frequently detected included indigo buntings, northern cardinals, tufted titmice, and yellow-breasted chats (Fig. 4). Preliminary results for woodland bird density for the 2016 breeding season in each forest types, ranged from birds/ha in willow oak to in sweet pecan (Fig. 2). During the 2017 breeding season 503 bird observations representing 36 different species during point count on the research site. Results from the 2017 density analysis ranged from birds/ha in sweetgum to birds/ha in sugar-persimmon (Fig. 3).
In regards to diversity, Shannon’s Diversity Indices for the 2016 breeding season ranged from in sweetgum to in sweet pecan (Table 1). Diversity indices for the 2017 breeding season ranged from in sugarberry-persimmon to in sweet pecan (Table 2), making this forest type the highest in diversity over the two year data collection.
2016 Season
2017 Season
Introduction
Bottomland hardwood forests cover about 2.8 ha of the original 10 million ha that once existed in the southeastern United States. This loss led to an emphasis on afforestation of retired agricultural land. As these afforested stands mature, topographic variation can cause certain tree species to become more established in certain areas compared to others. This can lead to an afforested stand with forest types with areas of differing tree species. Our objective is to evaluate how these differing forest types influence the density and diversity of breeding woodland birds in a Louisiana afforested bottomland hardwood forest.
Acknowledgments
Special thanks to Mr. Gerald Nichols and NRG Energy Inc. for access to their property for data collection, and the Louisiana Tech School of Agricultural Sciences and Forestry for use of equipment and facilities. This research is being financially supported by the USDA National Institute of Food and Agriculture, McIntire-Stennis project LAZ00081(accession number ).
Figure avian density (birds/ha) analysis in each of the 7 different forest types at the afforested bottomland hardwood study site.
Figure avian density (birds/ha) analysis in each of the 7 different forest types at the afforested bottomland hardwood study site.
Table avian diversity and equitability data analysis in each of the 7 different forest types at the afforested bottomland hardwood study site.
Table avian diversity and equitability analysis in each of the 7 different forest types at the afforested bottomland hardwood study site.
References
Nuttle, T. and L. W. Burger Birds of bottomland hardwood reforestation sites: patterns of occurrence and response to vegetation structure. Pages 353–371 in L. H. Fredrickson, S. L. King, and R. M. Kaminski, editors. Ecology and management of bottomland hardwood systems: the state of our understanding. University of Missouri-Columbia, Gaylord Memorial Laboratory Special Publication Number 10, Puxico, Missouri, USA.
Strozier, S. T Evaluation of planting techniques, stand structure, and composition of a bottomland hardwood afforestation in the Red River Alluvial Valley. M.S. Thesis. Louisiana Tech University, Ruston, Louisiana, USA.
2016 Season
2017 Season
Figure 1. The location of the 809-ha afforested bottomland hardwood forest owned by NRG Electric, Inc. in Desoto Parish, Louisiana. Also included are point locations where avian point count surveys will be conducted June-August,