Multiple Climate Signals Characterize Cassiope Mertensiana Chronologies for a Site on Mount Rainier, Washington, USA

Abstract

This study investigates the nature and strength of the climate signals that characterize an alpine dwarf-shrub, Cassiope mertensiana (mountain bell heather). For the first time, we present six new C. mertensiana chronologies (two growth, two reproduction, 1963-2004; δ13C, δ18O, 1975-2005) based on 14 plants from a subalpine meadow site on Mount Rainier, Washington, USA. Correlation, factor, and multivariate regression analyses revealed that multiple and different climate factors control the chronologies. Annual growth and leaf production are controlled by previous- and current- year growing season and previous-year February temperature. Warm growing season temperatures positively influence soil nutrient uptake rates, while winter temperatures may temporally alter moisture distribution resulting in reduced plant growth. Annual flower bud production is controlled by previous and current-year mean summer, growing season, and annual dewpoint temperature. Annual flower production is controlled by current-year mean spring, summer, growing-season, and annual dewpoint temperature. Increased atmospheric moisture facilitates open stomata, higher photosynthetic activity, and increased reproduction. Previous-year growing season and annual dew-point temperature, fall relative humidity, and temperature control δ18O values, indicating the influence of stomatal conductance on evaporative enrichment. Previous-year spring dewpoint and annual maximum temperature control δ13C values, suggesting the values are a product of photosynthetic rate controlled by temperature or photon flux.