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

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