Perils and Promise of Pinus aristata

Abstract:

Overshadowed by the more charismatic Great Basin Bristlecone Pine (Pinus Longaeva), Rocky Mountain Bristlecone Pine (Pinus aristata) provides valuable insight into the climate of the central Rocky Mountains of Colorado and New Mexico. With 2500-year-old living trees and remnants dating back 2800 years, this "shorter-lived" taxon of the bristlecone family has immense potential for valuable climate reconstruction. As with P. longaeva, the extremely slow growth of P. aristata results in long-term smoothing of climate information contained in the tree-ring widths. Adjacent trees have a mix of climate sensitivities related to variable topographic and elevational characteristics of the site. Because the trees climate-response is masked by low-frequency smoothing while also dependent on microsite characteristics, an abundance of caution must be taken when using P. aristata chronologies in climate reconstructions.

Using 5 previous and 6 new/updated P. aristata collections from Colorado and New Mexico, our study examines the climate-growth correlations contained within bristlecone pine. EOF analysis is applied to the 11 ring-width chronologies and to the individual trees ring-widths within those chronologies to investigate common growth signals at the inter-site and intra-site (respectively) domains. Growth patterns revealed by the EOF process are spatially correlated with gridded climate records to assess the influence of climate parameters on growth. In addition, by adopting an approach of previous researchers, tree growth records are correlated with site-specific climate records prior to the application of hierarchical cluster analysis on the correlation matrix. The cluster groupings are combined into chronologies and correlated with gridded climate data in the same manner as the EOF results to assess climate sensitivities. We highlight the resulting tree growth/climate associations while also assessing strengths and challenges of P. aristata for use in dendroclimatic reconstruction.