COS 41-9
Climatic influences on episodic post-fire conifer establishment in low-elevation ponderosa pine forests of the Colorado Front Range
Our research examined climatic influences on episodic post-fire conifer establishment in low-elevation, ponderosa pine (Pinus ponderosa) forests of the Colorado Front Range. Given observations of limited post-fire regeneration in several recent burns of the study area, we examined what role climate variability may play in explaining regeneration success or failure after fire. Our specific research objectives were to: (1) construct a dataset of annually-resolved establishment dates for post-fire ponderosa pine and Douglas-fir (Pseudotsuga menziesii) juveniles, and (2) assess climatic influences on temporal patterns of conifer establishment. We hypothesized that conifer establishment would be concentrated in years of above-average moisture availability and that little or no establishment would occur in drier years.
Results/Conclusions
We developed a large dataset (n = 413) of annually resolved establishment dates for post-fire juvenile ponderosa pine and Douglas-fir collected from five recent burn areas (year of fire: 1988 to 2003) of the Colorado Front Range. Annually-resolved estimates of tree age were obtained by harvesting juvenile conifers and dating the innermost ring at the root-shoot boundary. Our findings indicate that post-fire establishment was highly episodic and was concentrated in years of above-average moisture conditions. Specifically, establishment occurred most abundantly in years of high summer rainfall, when PDSI values were positive. Establishment was generally low or absent in drier years. Our research supports the idea that in the context of changing climate conditions, wildfires can serve as catalysts of rapid change. Climate conditions of the future may be increasingly unsuitable for post-fire ponderosa pine and Douglas-fir establishment at the lower elevational ranges of these species and thus different vegetation communities may develop and persist after disturbances.