Abstract: Winter climate change decreases snow cover and increases the frequency of freeze-thaw cycles and freeze-thaw cycles have been shown to damage adult trees, seedlings, and saplings. Understanding seed responses to freeze-thaw cycles is critical because tree species rely on the ability of their seeds to endure the winter climate and germinate in the spring. The objective of this study was to quantify the relationship between snow cover and freeze-thaw cycle frequency in a mixed deciduous forest in central New York, and use these data to parameterize a growth-chamber experiment studying the response of different tree species’ seeds to freeze-thaw cycle frequency. We hypothesized that decreased snow cover will cause more extreme temperature fluctuations in the below-ground environment which will lead to reduced or premature seed germination, but that this pattern might differ among species. Snow depth was measured every two weeks at 10 plots during the winter of 2021-2022. iButtons at these plots recorded soil temperature every 6 hours, this data was used to calculate the number of freeze-thaw cycles. Average snow depth was 38.276, 95% CI [35.07, 41.46]. Average number of freeze-thaw cycles was 7.47, 95% CI [2.42, 12.52]. Snow depth was not strongly related to freeze-thaw cycles (r= 0.06, P=0.885). The weak correlation between snow depth and freeze-thaw frequency likely reflects low variation in snow cover across our study area. Additionally, within-plot variability was high, suggesting that, in addition to snow depth, local factors such as aspect, elevation, and tree cover also play an important role in shaping winter climates experienced by plants.Currently, we are conducting a series of growth chamber experiments to examine how increasingly frequent freeze-thaw cycles affect seed germination of 5 native and 3 non-native tree species. We expect that seeds exposed to frequent freeze-thaw cycles will exhibit reduced germination and growth and that this effect will be more pronounced in seeds from species with more northern native latitude ranges. This work aims to develop an understanding of how tree species composition of northern temperate forests may shift with climate change, allowing us to identify which species will benefit and suffer from climate change. Our results may also help inform future reforestation and forest management efforts by identifying species that can tolerate more frequent freeze-thaw cycles.
