Edgy Pines: The effects of climate change on growth trends of Pinus banksiana and Pinus rigida at opposing range margins

Edgy Pines: The effects of climate change on growth trends of Pinus banksiana and Pinus rigida at opposing range margins Linh Le

SPECIES RANGE MARGINS AND CLIMATE CHANGE

EVIDENCE OF CLIMATE CHANGE

Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer. (Graph adapted from Mann et al., 2008.)

SPECIES GROWTH AT RANGE MARGINS

Climate change has significantly affected the distribution of species by either expanding or restricting suitable habitat depending on species-specific responses to climatic factors.

As a precursor to actual range shifts, increasing or decreasing trends in growth may allow us to predict long-term species trajectories.

OBJECTIVES

To analyze growth trends in jack pine and pitch pine populations in northern New York.
To model growth trends as a function of regional climate variables such as temperature and precipitation.

METHODS

Study Sites

Range map of jack pine and pitch pine along with the study site at Altona Flat Rock, Gadway Pine Barren and Clintonville Pine Barren

SAMPLE COLLECTION

Collected and measured the ring width of jack pine and pitch pine cores

GROWTH-TREND ANALYSIS

Detrended ring-widths using a negative exponential model in the dplR package
Modeled annual ring widths against a suite of temperature and precipitation variables (long term and short term) in R-programming environment.

Raw series (above) and fitted negative exponential curve (below) of the ring width index

RESULTS

Ring-width index of a and c) jack pine and b and d) pitch pine (AL PIBA – Altona Jack Pine, GA PIBA – Gadway Jack Pine, AL PIRI – Altona Pitch Pine, CL PIRI – Clintonville Pitch Pine) over the period from 1868-2019. In each panel the black line represents the detrended master chronology, with the red line being 20-year moving average. Gray shading shows the sample depth through time.

Lake Champlain Basin long-term temperature records over the past century compiled from eight regional weather stations. Records are shown as the anomaly from the 1880-2019 average. Solid black lines represent the fitted line from a generalized additive model (GAM) with the shaded area representing the 95% confidence interval.

Lake Champlain Basin short-term temperature records and Burlington precipitation records over the past decades. These are the temperature and precipitation variables that showed the strongest correlation to the growth of four pine populations in the short-term model. Temperature records are shown as the anomaly from the 1941-2018 average while precipitation records are shown as the average measurements for each season from 1941-2018. Solid black lines represent the fitted line from a generalized additive model (GAM) with the shaded area representing the 95% confidence interval.

CONCLUSIONS

Jack pine growth have been relatively stable and expressed no directional changes over the past century
Pitch pine growth, particularly in Altona Flat Rock, showed an increasing trend in growth since the 1960’s and a slight decrease in ~1980
In the long-term model, there is a weak relationship between temperature data and growth trend even when the variables are shown to be significant
In the short-term model, there is a stronger relationship between precipitation data and the growth trend in pitch pine
Species range limits are not determined solely by temperature but other limiting factors

Appreciate