Pinus leiophylla, or Chihuahua pine (PILE), and P. ponderosa, or ponderosa pine (PIPO), are two wide-ranging North American species with distributions that overlap in Arizona, USA. We compared the growth of 58 trees from three study sites over an elevation gradient at the northernmost point of PILE occurrence. Because the PILE trees were growing at the extreme edge of the species' range, we expected that PILE sensitivity to climate would be higher and growth performance would be reduced compared to PIPO. From 1918 to 2017, the study area became drier and warmer with precipitation declining by ~9% while temperature rose by ~5%. We found that PILE tree-ring indices were more sensitive in terms of average year-to-year percent variation than those of PIPO and had higher variability in tree-ring variation in the 10 wettest vs. the 10 driest years. But PILE displayed higher absolute diameter growth rates as measured by basal area increment (BAI) and was less negatively correlated with warm monthly temperatures. Within species, low-elevation trees of both species tended to have greater sensitivity to climate over all variables assessed, but the differences were not statistically significant. The overall assessment of growth of paired trees of the two species showed the locally rare species PILE to perform approximately equally as well as the dominant species PIPO. Species migration is reshaping global forests but species found predominantly in Mexico with distributions coinciding closely with national boundaries have received insufficient research attention in the USA. We recommend cross-border, climate-focused, comprehensive studies on PILE and other species likely to migrate northward to provide critical information for conservation and management of forest resources.
- Pinus leiophylla
- Pinus ponderosa
- tree-ring index
ASJC Scopus subject areas
- Global and Planetary Change
- Nature and Landscape Conservation
- Environmental Science (miscellaneous)