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I did a short section hike along the Long Path in New York State today along the Jenny Lane Trail in The Minnewaska State Park Preserve. Shortly after leaving the trail head, I came to a large patch of forest where much of the undergrowth was dead, but the surrounding trees looked healthy. It was puzzling, so I started looking for clues to see if I could figure out what had caused it.
I had taken a walk in the same area earlier in the week and knew that the area was under a lot of stress from drought conditions. Some of the major creeks that I like to visit in the area are bone dry, down to the riverbed. But, there was still plenty of green shrubbery on the ground and in the trees, so this die-off had to have taken place sometime in the past.
I suspected fire, and thought back to a book I had read last year, and reviewed on section hiker, called Reading the Forrested Landscape by Tom Wessels. In it, he guides readers through a series of observational exercises that show you how to tell the natural history of a wooded area by examining tree growth, species distribution patterns, soil composition, and the historic influence of man. Tom is the Sherlock Holmes of the forest, if you ask me. Fascinating and useful stuff.
But fire wouldn't explain why the surrounding trees were still lush and growing normally. I needed to collect more evidence, so I continued hiking up the north side of the Shawangunk Ridge, west of the famous Trapps rock climbing cliffs.
The surrounding forest started to thin out and there were a lot of dead trees around me, east and west along the ridge, with the exception of Pitch Pines, which were flourishing. Pitch Pines have thick protective bark which makes them a very fire resistant species which competes well against other hardwoods in areas that suffer from fire.
Continuing on, I started to see charred tree trunks around me. This confirmed my hypothesis, that fire had swept through the area. I suspect it was probably started by lightning given that I was so near the top of the ridge. Lightning however, doesn't explain why the brush towards the base of the ridge was burned, but the surrounding trees were not.
To explain this, I did a Google search and found that the Jenny Lane Trail had been closed in April 2008 due to an extensive fire in the area, that had been put out by heavy rain. This would explain the pattern of the burn that I observed. If the fire started at the top of the ridge, it makes sense that the understory brush and trees would have both been burned out. If the fire then proceeded downhill, to the north, the underbrush would have likely caught fire first, before being extinguished by the rain. This might explain why the trees to the north suffered far less damage than those at the top of the ridge.
That makes sense. Does anyone local to the New Paltz or the Kerhonkson, NY area know what actually happened?
What a cool book. I added it to my Amazon cart and think my sister and dad would love it, too.
You'll love it. It totally opened my eyes on how to read a forest and understand how all of the species and landscape interact and change over time.
Just to add, I had drinks later in the week with a conservation biologist who works for the Mohonk preserve, and she confirmed that there had been a fire on the mountain.
Fire intensity can vary a great deal depending on topography. Typically lower areas exhibit lower intensity fires and as the fire moves up hill it is preheating vegetation above it and fire intensity can increase dramatically which would explain the dead overstory trees. If the fire started on an upper slope it could back burn down into lower areas, these fires are typically lower intensity and move slower. Imagine a fire moving into the wind as opposed to with the wind. Human caused fires are much more prevalent than lightning fires in the Appalachians so it may have been a human caused fire on a lower slope that began burning understory and increased in intensity causing overstory mortality.
Pitch pines are fire dependent (require fire to reproduce) and are resistant to fire effects. They need lots of sunlight and relatively bare ground to seed, both conditions occur after fires. In areas where fires have not occurred recently they can be crowded out by hardwoods like oaks and eventually shade tolerant species such as maples.