Effects of climate change on the growth of Pinus banksiana and Pinus rigida at opposing range limits.
Zachary Hart, Madelyn Lehman, Linh Le, Michael Hurban, and Mark Lesser
Range limits of jack pine (Pinus banksiana) and pitch pine (Pinus rigida) and our study area
A species' range is the area that the individuals of the species can both survive and reproduce. These ranges are determined by physiological attributes, interactions with other biota, and also dispersal capabilities. At the Altona Flat Rock both jack pine and pitch pine are present, however they are at opposing range margins with jack pine near its southern or equatorial limit and pitch pine at its northern or polar limit (fig 1.).
Figure 1. This map shows the range limits of jack pine and pitch pine. The inset shows the location of the Flat Rock in Northern New York as well as our coring locations represented as color coordinated points representing where cores of each species were collected.
Our Hypotheses
If climate is the limiting factor for the ranges of both jack pine and pitch pine we hypothesized that the climatic conditions would potentially become more unsuitable for jack pine leading to a reduction in growth overtime, and potentially more suitable for pitch pine causing an increase in growth. However, if climate is not the determining factor than we could potentially see growth have no directional response to the climate variables.
Methods
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Increment cores were collected from 132 jack pine and 75 pitch pine in 2018 and 2022.
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Cores were mounted and incrementally sanded until cell structure was visible.
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The cores were measured on a Velmex Measuring bench using the measureJ2X software to the nearest 0.001 mm.
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Cores were cross dated using Cofecha.
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0.282 Correlation
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Growth trends were analyzed in R using the dplR package.
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Ring widths were detrended to account for biological growth trends by fitting a negative exponential curve to each of the raw ring width series.
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Detrended ring widths (rwi) were modeled against temperature, precipitation, and North Atlantic Oscillation variables for the years 1941 to 2018.
Results and conclusions
Jack pine growth when modeled against the suite of climate variables showed statistically significant responses to 21 variables (Table 1). The climate variable with the largest effect on growth is February Temperature. February temperature showed a negative quadratic relationship with jack pine growth (fig 2).
Table 1. The effect size of all significant climate variables on jack pine growth, with standard error. Variables denoted with a ^2 indicate a quadratic relationship.
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Figure 2 . The relationship between climate variable and ring width index of jack pine (left) and how the climate variables change overtime (right). The dotted lines on the climate variable over time plots is the inflection point of the quadratic relationship the climate variable has with jack pine ring width index.
When the climate data was modeled against pitch pine growth 30 variables showed a statistically significant relationship (Table 2). For pitch pine Fall temperature showed the largest effect size with a positive linear relationship (fig 3).
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Figure 3. The relationship between detrended pitch pine growth and climate variables (left) and how the climate variables are changing over time (right) are shown. The dotted line in the summer precipitation over time and December NAO over time is the inflection point of the quadratic relationship those climate variables have with pitch pine rwi.
Table 2. Effect sizes of each climate variable that showed a significant relationship with pitch pine growth. Standard error is shown. Variables with a ^2 indicate a quadratic relationship.
When looking at the overall growth trends (fig 4) we see that the growth trends for jack pine are non directional. This leads to the belief that the range of jack pine is not limited on its southern limit by climate. The growth of pitch pine however has seen a general increase in growth since the 1960s meaning that the warming climate is allowing for better growth and the potential of pitch pine to shift its range poleward.
Figure 4. Master chronology for jack pine and pitch pine. Smoothed growth trends are shown as the dark line. Sample depth is shown as the shaded area in both plots.
Acknowledgements
I would like to thank SUNY Plattsburgh, The Center for Earth and Environmental Science, and the Miner Institute. I would also like to thank Meghan Bargabos, Caley Doell, the fall 2022 Forest Ecology class, and Dr. Mary Alldred.
