The shortleaf pine (Pinus echinata Mill.) ecosystem has been on a slow decline over the last 40 years throughout most of its range across the eastern USA. Most of this decline has been caused by cutting, species replacement, and ineffective fire management. Several organizations have studied various means to restore and increase the area of this important eastern pine ecosystem. One important component of this effort is to assess the amount of forest land with shortleaf pine primary regeneration (seedlings <2.54 cm in diameter but ≥ 30 cm tall). We used data from the USDA Forest Service, Forest Inventory and Analysis (FIA) program, to determine the extent and condition of shortleaf pine primary regeneration. Using the premise that all overstory stand components originated through the seedling stage, an evaluation of the seedling component of shortleaf pine seedlings is important for evaluating, understanding, and managing for the future sustainability of the ecosystem. Our assessment determined the amount of forest land across 20 eastern states with shortleaf pine seedlings; the structural component was defined by seedling density, dominance, species richness (S), and evenness metrics. For the latter the McIntosh Evenness Index (MEI) was used.
Results/Conclusions
Across the eastern U.S. there were 9,651,874 (±61,736 C.I.) ha of forest land with at least 14 shortleaf pine trees per ha (TPH) that were ≥2.54 cm dbh (equivalent to one tree per sample unit [SU]). Of these forest stands with a shortleaf pine presence only 2,022,622 (±46,870 C.I.) ha had shortleaf pine seedling regeneration present. Here, the overall seedling layer structure showed an average density of 7,182 seedling TPH, seedling (S)=7.2 SU-1, and an MEI=0.59, while the shortleaf pine component averaged 1,430 TPH. The seedling density, richness, and evenness metrics of shortleaf pine stands averaged higher east of the Mississippi River but the regeneration prevalence of shortleaf pine seedlings was higher west of the river. Of concern is the lack of shortleaf pine regeneration in stands where shortleaf pine was the number 1 or 2 ranked canopy dominant. There were 3,540,491(±59,685 C.I.) ha in these types of stands without shortleaf pine seedlings present. The study provides evidence of the high amount of shortleaf pine forests without seedling continuity, a necessary component for the maintenance of the ecosystem. Describing and documenting initial or baseline states of ecosystem components is an important first step in ecosystem risk assessment.