The Burning Question: How is structural diversity shaped by wildfire at a Jack Pine barrens?
James Wholey, Zachary Hart, Meghan Bargabos, and Mark Lesser
Center for Earth and Environmental Sciences, SUNY Plattsburgh
Background
Our study area, the Altona Flat Rock, is a sandstone pavement pine barrens in northeastern New York dominated by Pinus banksiana (Jack Pine), a fire-dependent serotinous species, and an understory composed primarily of Vaccinium angustifolium (Lowbush Blueberry) and Gaylussacia baccata (Black Huckleberry). The Flat Rock barrens is surrounded by northern hardwood forest making it a unique habitat type for both wildlife and bird species. Within the pine barrens, wildfires have occurred in different areas in 1919, 1940, 1957, and 2018, which, along with silvicultural practices in 1998, have created a mosaic of stand ages (104, 83, 66, 5, and 25 years old, respectively), and corresponding structural attributes, across the ecosystem.
Objectives
Our objective was to determine how disturbance history has shaped structural diversity across a northern New York pine barrens ecosystem. Quantifying Forest structure in each of these patches, and determining overall structural diversity, will help interpret wildlife and bird community findings, and begin to inform best-management practices on how different patch ages, sizes, and configurations can maximize diversity across all levels of the ecosystem.
Methods
Field Work:
To determine how forest structure changes between patches we randomly selected 3 plot locations in each of 20, 1 km² grid cells that spanned the Flat Rock and parts of the surrounding hardwood forest (60 plots total). At each plot center, we used variable distance sampling to tally trees by species and diameter with tree height being measured using a clinometer. Canopy closure was measured with a densiometer. We tallied all coarse woody debris that was >10 cm diameter and >1 m in length. We quantified relative abundance of understory species in three 1 m² subplots within each plot. Subplots were located 5 m from the plot center at 0, 135, and 225 degrees. We also cored three trees at each plot containing live Jack Pine.
Analysis:
Density and basal area were calculated for each species at each plot. Tree cores were mounted and sanded to 400 grit. To determine tree age, annual rings were measured using a Velmax Measuring Bench and the J2X software. Tree cores were cross dated using COFECHA and final ages were adjusted for coring height. To visualize forest structure across the entire Flat Rock system we used the Kriging spatial analyst tool with default settings in ArcGIS pro which allowed us to interpolate structural attributes between points.
Results
-
Coarse woody debris showed no significant difference between forest types, Jack Pine stands showed a positive trend as stand age increased.
​
-
For average tree height, Hardwood stands were significantly different from all Jack Pine stands except the 1997-2017 age range, Jack Pine stands showed a positive trend as stand age increased.
​
-
Live Density showed no significant difference between forest types, Jack Pine stands showed a positive trend as stand age increased.
​
-
Live basal area showed Hardwood stands being significantly different from all Jack Pine stands except the 1940-1956 age range, Jack Pine stands showed a positive trend as stand age increased.
​
-
Canopy closure showed no trend in Jack Pine stands relative to stand age, The 1910-1939 age range showed high variability, most likely because as trees die, there will be more open patches of canopy.
​
-
Blueberry cover showed Hardwood stands being significantly different from all Jack Pine stands, There was no trend in Jack Pine stands relative to stand age.
​
-
Overall, even though there is no significant difference between Jack Pine ages in most attributes, there is a positive trend for most attributes as stand age increases.
