As forest communities continue to experience interactions between climate change and shifting disturbance regimes, there is an increased need to link ecological understanding to applied management. Limber pine (Pinus flexilis James.), an understudied species of western North America, has been documented to dominate harsh environments and thought to be competitively excluded from mesic environments. An observational study was conducted using the Forest Inventory and Analysis Database (FIAD) to test the competitive exclusion hypothesis across a broad elevational and geographic area within the Intermountain West, USA. We anticipated that competitive exclusion would result in limber pine's absence from mid-elevation forest communities, creating a bi-modal distribution. Using the FIAD database, limber pine was observed to occur with 22 different overstory species, which represents a surprising number of the woody, overstory species commonly observed in the Intermountain West. There were no biologically significant relationships between measures of annual precipitation, annual temperature, or climatic indices (i.e. Ombrothermic Index) and limber pine dominance. Limber pine was observed to be a consistent component of forest communities across elevation classes. Of the plots that contained limber pine regeneration, nearly half did not have a live or dead limber pine in the overstory. However, limber pine regeneration was greater in plots with higher limber pine basal area and higher average annual precipitation. Our results suggest limber pine is an important habitat generalist, playing more than one functional role in forest communities. Generalists, like limber pine, may be increasingly important, as managers are challenged to build resistance and resilience to future conditions in western forests. Additional research is needed to understand how different silvicultural systems can be used to maintain multi-species forest communities.
Bibliographical noteFunding Information:
This study was supported in part by a Utah Agricultural Experiment Station (), and USDA Forest Service Forest Health Monitoring (INT-EM-B-14-01) (). Additional support for MAW came from the USDA NIFA National Needs Graduate Fellowship Competitive Grant (NO. 2011-38420-20087) () and the T.W. Daniel Endowment (). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Data were collected by USDA Forest Inventory and Analysis (FIA) Program. John Shaw, R. Justin DeRose, and other members of the Interior West Resource Inventory Team, RMRS Ogden provided advice on data analysis. Barbara Bentz, Sara Geoking, R. Doug Ramsey, and Kari Veblen provided valuable comments on earlier versions of the manuscript. Approved as Utah Agricultural Experiment Station journal number 8869.