The shrinking footprint of longleaf pine (Pinus palustris) in the southeastern United States

Background/Question/Methods

Longleaf pine (Pinus palustris Mill.) was once one of the most ecologically important tree species in the southern United States (U.S.).  Longleaf pine and the accompanying longleaf forest ecosystem covered vast swaths of the southern U.S.  Longleaf forests covered an estimated 92 million acres at their peak distribution, and represented one of the most extensive forest ecosystems in America. Only a fraction of the longleaf pine ecosystem remains today. Remaining longleaf pines are scarce compared to the historical extent, and are spread among eight southern states in largely fragmented stands. Additionally, scientists, conservationists, and land managers hypothesize that much of the remaining acreage is in poor condition. Therefore, it is imperative that longleaf pine receive continuous focused monitoring. Data from the Forest Inventory and Analysis (FIA) program of the USDA Forest Service covering a period between 1970 and 2010 were used to explore both temporal and spatial trends in longleaf pine population dynamics of the southern U.S. in order to better understand the potential future of the species.

Results/Conclusions

In 2010, 4.3 million acres of longleaf pine dominated forests existed across the south. According to broad-scale inventory data, longleaf pine forests are still declining. Considerable contraction of the geographic distribution of longleaf pine has occurred from 1970 to 2010. Contraction occurred on both the northern and eastern range boundary. The northern and eastern range boundary for longleaf pine, as sampled by FIA, contracted approximately 97 km and 51 km, respectively between the 1970’s and 2010. Within the contracting “footprint” of longleaf pine, 32 percent of counties with longleaf pine forests in the 1970’s have experienced significant (70 percent or greater) losses of longleaf dominated forest area. While losses occurred throughout the longleaf range, heaviest losses occurred along the gulf coast and in western Louisiana. Results indicate that considerable longleaf pine loss can be attributed to the conversion to the loblolly pine forest type. Longleaf pine forests represent an important resource in the context of the southern U.S. forest. While many conservation efforts have been and are currently active in efforts to reestablish longleaf forests across the south, these valuable forests continue to decline.