Meadow invasion from high-elevation spruce-fir forest in south-central New Mexico

Stands of corkbark fir-Englemann spruce were sampled on Buck Mountain (elevation 3,282 m) within the White Mountains of south-central New Mexico. A time series of aerial photographs suggests that adjacent meadows have been invaded by these high-elevation stands continuously oil the southwestern slope since the 1930s, although the forest-meadow boundary on the northeastern slope has been relatively stable for decades. To obtain baseline information about stands, and to assess patterns of encroachment into meadows, quadrats were established in intact forest on both the southwestern and northeastern slopes, and contiguous quadrats extended into the adjacent meadow. Increment cores were extracted from the two apparently oldest trees of each species within each quadrant (n = 53 trees) to estimate establishment dates. Based on field data and historical records, we conclude that climatic change is a more likely explanation for encroachment of trees into the adjacent meadow, rather than fire suppression or changes in grazing intensities at this site.