Trees offer innumerable benefits to wilderness and humanity, and so, we may feel a reflexive sadness when coming upon a dead or dying tree. However, at its death, a tree has really only reached the halfway point in its gift-giving journey. After having fallen, the ground it shaded for decades, maybe centuries, bursts with new life. Long dormant seeds soak up that sunlight and sprout. Small saplings that have grown slowly for years now leap up into the canopy. Each of these new species that emerges from the former shadow has the potential to transform the surrounding land, creating a much more dynamic ecosystem through a process called forest succession. Through this process, these spaces may transform into glades or meadows as sun-loving species quickly grow, sometimes offering berries and tender leaves as forage not found in darker woods.
Standing dead tree is called a snag. Keystone features of the landscape, these stumps are crucial for biodiversity. Lichens and mosses proliferate in the newfound sunlight and find easier purchase in wood softened by microbes, all of which attract insects and their predators. This decomposition makes the snag an extension of the forest floor reaching up into the canopy, greatly increasing the available surface area for life to act upon. Holes drilled by boring beetles and termites are enlarged by larger and larger creatures, until they can house owls, fisher-cats, and even bears. Without cavities of a certain size, some animals, like wood ducks, won’t feel at home even in a forest of large trees.
Eventually, the snag will fall, transforming once more, now into a nurse log. Despite being in a state of decay, the log still has an internal structure. Crisscrossed with fungal networks and insect tunnels, this matrix is a fertile substrate for seeds. Elevated above the forest floor, seedlings have more sunlight and protection from flooding. Fungi and mosses collect and hold on to water that would otherwise shed off the tree, which helps to maintain a humid environment. This speeds up decomposition, which provides a ready fertilizer. Some seeds, like those of ladyslippers and rattlesnake orchids, require this sort of fungal assistance to germinate.
Instead of breaking, a falling tree will sometimes lever its root ball out the ground, and leave behind a deep hole. This can elevate the surface roots, as well as a substantial amount of soil, large stones, and living plants many feet into the air. These decompose into paired formations called pit-and-mounds, or pit-and-pillows, and persist for many years. This altered topography offers a variation of microclimates, each a different niche to host a variety of organisms. The mound becomes a dry and sunny hillock; an island lifted above the understory. The neighboring pit is shaded and cool, and may even become a small wetland. By breaking open the forest floor, this phenomenon facilitates the creation of dens or nesting sites for animals who might have difficulty digging through roots and layers of duff (decaying vegetable matter).
On your next walk, spare a thought for these dead trees; Evidence of nurse logs lasts long after they disappear. Look for lines of trees inexplicably growing in a row. Find ‘floating trees’ where a nurse log or stump has rotted away and a successor tree has perched on a squid-like tangle of exposed roots. Search for seedlings nestled in bark or sprouting from a beetle’s tunnel, ready to begin the process anew.
Written by Justin Cifello, Wareham Land Trust Member and Volunteer