Our forests never sleep, even in winter!
Autumn leaves are dropping; starting an inevitable timeless recycling process that enriches the soil. You might think that once the leaves have all dropped, that forests begin to wind down for a long winter snooze.
But according to Dr. Emile DeVito, New Jersey Conservation Foundation’s staff biologist, critical ecological processes and fascinating animal behaviors begin in the fall and continue right through winter.
As Emile explains, falling leaves pile up on the forest floor. Water, molds, and other fungi combine to decompose the leaves, gaining energy from the tough lignin, which has the same chemical makeup as sugar and starch.
On sunny warm days, invertebrates living in the rich organic layer of the soil begin shredding and chopping up the softened leaves. As pieces get smaller, even more critters attack. By early spring, many nutrients will be newly available to the root and fungal mats in the dark, rich organic humus – the soil layer beneath the leaf litter in our forests.
If you’re a hiker, you've likely encountered forest floors free of leaves and humus, but instead sprinkled with little dirt-like ball bearings. You are walking on mineral soil particles that have been scrubbed of organic material and compacted into worm poop!
But most of the earthworms in our forests are non-native, invasive species. Unfortunately, European earthworms, and especially the recently-arrived Asian earthworms, break down leaf litter far too quickly, consume the nutrients, release carbon dioxide (CO2), and create ideal habitat for shallow-rooted invasive plants like garlic mustard and Japanese stilt grass. These plants also lower the natural acidity (raise the pH) of forest soils, encouraging more earthworms.
Why does worm poop matter? One reason is that New Jersey’s growing season has lengthened due to global climate change. Today, on warm, sun-facing slopes, especially in forests growing on former agricultural land, there is enough time in the fall and early winter for earthworms to virtually eliminate the autumn leaf litter. Without leaf litter and with little or no snow to cover the soil, the tiny dirt balls of worm poop are exposed to powerful winter rains. Soil erosion can be extreme and result in heavy siltation in streams and waterways, even within our forests.
Thankfully earthworms cannot get a strong foothold in the Pine Barrens. The pine and oak leaf litter decomposes very slowly due to sandy and acidic soils, and can get quite thick.
By about Halloween, all of the rare snakes in Pine Barrens forests have made their way back to their winter dens. But these snakes do not retreat into their dens for a long winter slumber. They seek refuge well below the frost line in cold but unfrozen soil at a constant temperature of about 36 degrees. Timber rattlesnakes in the Pine Barrens hibernate in cold water near unfrozen, running forest springs.
Recent radio-tracking studies of these rare snakes reveal that they emerge to bask in the sun on warm winter days. This may help their immune responses in fighting minor bacterial and fungal infections. Sometimes they even switch winter dens, moving cross-country in the middle of winter.
One massive adult male pine snake moved two-tenths of a mile in January. He may have followed the scent trail of a large, breeding age female that had gone that same way the previous September; this same male ended up following her very closely the next spring until breeding season arrived.
On humid late fall and winter evenings with temperatures above freezing, watch for male “winter moths” flying in your car headlights! You won’t see females unless you hike through the forest and find them sitting on tree trunks, as they have tiny vestigial wings and cannot fly. They simply emit their pheromones and wait for the flying males to catch their scent while on the wing.
Late fall brings one last flowering shrub. Witch-hazel, a common forest shrub throughout north and central New Jersey, blooms in October and November. This year, mild weather may allow the delicate yellow, threadlike flower petals to still be visible on Black Friday!
Watch for tiny flying insect pollinators that visit the witch-hazel, listen for the melancholy song of white-throated sparrows, and look for the many “winter finches” that migrate to New Jersey from the north to spend the winter here … in our forests that never sleep!
For more information about preserving New Jersey’s forests and other natural resources, visit the New Jersey Conservation Foundation website at www.njconservation.org or contact me at firstname.lastname@example.org.