Effect of climatic variability on δ13C and tree-ring growth in piñon pine ( Pinus edulis).

Understanding the response of long-lived species to natural climatic variability at multiple scales is a prerequisite for forecasting ecosystem responses to global climate change. This study investigated the response of piñon pine ( Pinus edulis) to natural climatic variability using information on physiology and growth as recorded in leaves and tree rings. δ¹³C of annual leaf cohorts (δ¹³C_leaf) and tree rings (δ¹³C_ring) were measured at an ecotonal/xeric site and a mid-range/mesic site. Ring width indices (RWI) were used to estimate annual growth of individual trees. Relationships between seasonal and annual climate parameters and δ¹³C and growth were investigated. δ¹³C–climate relationships were stronger for δ¹³C_leaf than for δ¹³C_ring especially at the xeric site. The mean monthly maximum summer temperatures over May through September (summer T_max) had the strongest influence on δ¹³C_leaf. There was a strong negative relationship between RWI with summer T_max and a strong positive relationship between RWI with October to October precipitation (water–year PPN) at both sites. This suggests that piñon pine populations could be vulnerable to decreased growth and, perhaps mortality, in response to warmer, drier conditions predicted by models of global climate change. [ABSTRACT FROM AUTHOR]