Wildlife Response to Wildfire in a Northern New York Jack Pine Barrens

Natural disturbances are an integral part of forested ecosystem function and successional pathways. In many forested ecosystems, wildfires are critical to shaping composition and structure, which, in turn, has major implications for wildlife usage and behavior. In July 2018, a wildfire burned 225 ha of the Altona Flat Rock pine barrens in northern New York. This event presented the opportunity to study how wildlife respond to the immediate effects of disturbance in this unique habitat but also how that response would change through time as regeneration progressed. Game cameras were deployed from September 2018 to September 2020 at two reference (unburned) and two disturbed (burned) sites within the pine barrens. We analyzed total and seasonal occurrences, to determine how usage differed between disturbed and reference conditions, and with time since disturbance. Additionally, for coyote (Canis latrans, Say), white-tailed deer (Odocoileus virginianus, Zimmermann), and snowshoe hare (Lepus americanus, Erxleben), we evaluated daily activity patterns and overlap to determine how predator–prey relationships differed between conditions, and with time since disturbance. Over 730 days, a total of 1048 wildlife occurrences were captured across 23 wildlife species. Fifty-seven percent of all occurrences were at reference sites with over 100 more occurrences than at disturbed sites; however, differences were most pronounced immediately following the fire and overall occurrences have grown more similar between the sites over time. Specifically, deer and hare were found more often at reference sites immediately following the fire, but shifted to using both conditions equally by the first growing season. Habitat overlap among sympatric prey (deer, hare) can be explained by understory regeneration increasing foraging opportunities and concealment cover in the disturbed condition, while predators (coyotes) tracked prey availability regardless of the habitat condition. This study provides wildlife management guidance on habitat use and response to disturbance for these unique sandstone pavement barrens.

Borehole equilibration 2.0 or how to chase tracer pulses in a forested ecosystem

<p>Identifying tree water sources has long been an issue since obtaining samples was labor intensive and lacked high time resolution because of the destructive sampling procedure. It was previously shown that the “borehole equilibrium method” (Marshall et al. 2020) allows in situ measurements of xylem sap isotopic composition. While the advantage in using this method is its ability to monitor isotopic composition of xylem continuously and rapidly with immediate data availability, disadvantages are the limited number of trees that can be observed and that the laser has to be present in the field. Here, we propose cheaper and more field-deployable elaboration of the method based on the same principle as to use for tracer pulse-chasing experiments in forested ecosystems.</p><p>We installed boreholes in tree stems and sealed them on both sites using brass fittings with a pierceable chlorobutyl septum. The water vapor inside the sealed borehole was assumed to reach isotopic equilibrium with the liquid water in the xylem due to diffusion within seconds and was sampled using gas-tight syringes. The 20ml sample was then injected in a dry air stream connected to a Picarro L2130-I cavity ring-down absorption spectrometer (CRDAS). Standards of known isotopic composition were injected the same way. The peaks, rather than plateaus, of isotopic ratios measured from these injections were weighted by the water vapor amount, giving results accurate enough to distinguish between xylem water of natural abundance and water enriched in deuterium (average SD for <sup>2</sup>H 5.2‰ and <sup>18</sup>O 1.9‰ for natural abundance samples). To test this method in the field, we labeled 1m<sup>2</sup> of soil at different soil depths with 15.5 L of water enriched in <sup>2</sup>HHO (δ<sup>2</sup>H +220000 ‰) in a Scots pine forest in northern Sweden. Trees within a 10m radius from the labeled center were monitored continuously, allowing daily measurements of up to 120 trees for six weeks. Depending on soil depth the uptake dynamics varied over time, with the peaks from the shallowest soil injections  occurring within two weeks, while for the deeper soil layers the contribution to transpiration lagged behind approx. four weeks, likely due to a combination of lower root density and reduced hydraulic conductivity at greater depth.  The strength of the peaks was correlated with distance from the labeled soil patch.</p><p>We were able to show that this method works to chase an artificially enriched water pulse through a natural forested ecosystem. At the same time, this adaptation allows the method to become even cheaper than its precursor as it requires much less tubing and fewer fittings. Lastly, we consider it more field-deployable because it does not require the CRDAS to be in the field.</p>