Will Jaremko-Wright, New Mexico Highlands University, Department of Natural Resources Management, wjaremko@live.nmhu.edu (Presenter)


Piñon-Juniper woodlands of the southwest have been experiencing both geographic and population expansions throughout the vegetation types range. In New Mexico, stands of one-seed Juniper (Juniperus monosperma) and less commonly two-needle Piñon (Pinus edulis) have been observed encroaching into previously non-woodland areas, specifically in the mesa, valleys, and highland plains region of northeastern New Mexico (MLRA 70A, 70B, 70C). Expansion of Piñon-Juniper extends further into adjacent plant communities across the landscape in regeneration waves characterized by stands with distinct age structure or characteristics. Source stands of older, pre-settlement trees, likely occurs in fire refugia sites with the newest ‘waves’ found with increasing distance in mesic, lower landscape positions. Landscape gradients associated with topographic positions and site quality of Piñon-Juniper stands were investigated as potential explanations for observed encroachment dynamics. Stand age structure, relative growth rate, and fine fuel loads were collected and analyzed against the topo-edaphic features of the site. Variations in one-seed Juniper sex ratios in response to environmental conditions along a gradient of decreasing stress was also investigated as a potential mechanism in Juniper encroachment feedback processes. Preliminary results are presented and discussed here. This research continues the efforts to better understand Piñon-Juniper expansion across landscapes and to develop sound information for management decisions and directions.