What is the sound of a fallen tree?
To me, a fallen tree sounds like “uncertainty”. Let me explain.
In 2011 and 2012, Hurricanes Irene and then Sandy swept the mid-Atlantic region of the eastern United States, including Nolde Forest State Park, in Cumru Township of Berks County. The gale-force storms blew down a swathe of trees in a stretch of contiguous forest. The windfall created a large opening in the canopy, allowing precious sunlight to reach to the dormant forest floor.
But what would come next from this unexpected disturbance? Did these hurricanes bring destruction or the start of something new?
To look forward, we must first turn back.
What we know today as the Nolde Forest State Park was once working land, historically used for agriculture, charcoal, and hard wood production. These activities all but deforested the land, leaving a lone white pine tree amidst the industry. Then, circa 1900, these 600 acres were purchased by the enterprising Jacob Nolde, who enlisted hundreds of skilled laborers to plant half-a-million young pine trees across the property.
View of the windfall at Nolde State Forest in 2013.
Nearly 30 years later the Nolde’s hilly, 600-acre meadow had transformed into a successful conifer plantation and early forest; the seed of the State Forest which we enjoy today. The transformation facilitated by Nolde is not unsimilar to the process of forest succession that occurs naturally, without human intervention.
Forests have lifecycles, marked by changes in their physical and community structure. Beginning at the earliest stages, forest edge or fringe habitat cedes to shrubs, reeds, and meadow plants. At the other end of this gradient is forest core habitat, the most mature and homogenous areas of forest denoted by their distance from the nearest forest edge.
Imagine for a moment that each skin cell on your arm is a tree in a large forest. The oldest and most mature (or ill) eventually reach a point where reproductive capability declines or outright fails. Time degrades all things, which necessitates renewal; these old cells slough off creating space for new vitality to move in. So it goes with forests. A large windfall resets the stage for forest succession to begin anew.
When I say that a fallen tree is the sound of uncertainty, I mean to convey that it is not necessarily a negative thing. Of course there are obvious concerns.
Like with skin cells, wounds to the forest not closely tended may fester. Proper land-use practices promote better healing and even healthier genetic stock among desirable species (Rhemtulla, Mladenoff, & Clayton, 2009). This is the basis for adaptive timber management, wherein tree removal is wielded strategically to aid in forest succession and structure.
Stratified forest ecosystems, with bespoke habitat structures from forest floor to canopy, produce a stabilizing effect benefiting the entire forest ecosystem. Whereas uniformly structured or fragmented forests marked by less core habitat and a greater proportion of edge, support less biodiversity (Hoover, Brittingham, & Goodrich, 2024).
View of a healthy, stratified portion of Nolde State Forest.
In the case of Nolde Forest State Park, the unexpected windfall created an opportunity for the forest’s stewards – Pennsylvania Department of Conservation of Natural Resources (PA DCNR) – to initiate and study park-wide adaptive timber management. The PA DCNR established two study sites to complement the blowdown area: a clear-cut site where all trees were felled and a selectively cut forest site. These three study sites were paired with nearby sections of forest unaffected by damage or by harvest, providing the “natural” data to which the disturbed areas of the park could be compared.
The blow-down site represented a typical storm disturbance, which arbitrarily damages or fells trees. The clear-cut site intentionally simulated a large and indiscriminate removal of vegetation, such as by wildfire. Finally, the select-cut site mimicked a more targeted die-off, such as when a disease impacts just one tree species, providing key insights into the forest community’s response to such emergent threats.
Assessing the year-to-year changes occurring within the management areas will allow the DCNR to determine best management practices for later implementation and further prepare their response strategies for sudden or unanticipated changes to the forest’s character.
This figure compares the three treatment sites – the natural blowdown area, the select-cut site, and the clear-cut site – in terms of species diversity where non-native, invasive species are shown in shades of red and native, woodland species are shown in shades of green.
Between 2013 and 2020, researchers at Albright College monitored these experimental disturbance sites and uncovered a rather complicated relationship wherein the areas affected by disturbance experienced rapid declines in plant species biodiversity after just two years (Osgood & Mech, 2020). Despite the differences in habitat structure between the three tree removal sites, all experienced similar declines in native species dominance, suggesting that the nature of disturbance alone does not dictate the quality of the regrowth.
But early signs of weakened native dominance do not capitulate failed stewardship. They signify that current strategies for succession do not account for one or more variables affecting regrowth, or that prior efforts were simply insufficient in scale for overcoming non-ideal species like Japanese stiltgrass (Microstegium vimineum), which was awakened by the introduction of unfiltered sunlight to the forest floor.
Within the seed bank, an unquantifiable number of seeds and spores hide, waiting for the opportune conditions to germinate. The battle for control of the forest’s future begins after this early successional stage – as the first colonizers reveal themselves – and is a constant endeavor thereafter.
These early invaders quickly capitalize on limited understory resources. An initial assessment of Nolde Forests’ study sites determined that the sudden boom of invasives was a consequence of speed: our native forest species simply require more time to develop and recolonize than the non-native competitors (Osgood & Metz, 2014). Often, reforestation requires two or more full growing seasons before any visual cues hint at success.
Aggressive though they are, the key to victory is persistence. Diligent invasive prevention and native replacements pave the way to a stable forest ecosystem. In the case of Nolde Forest, the PA DCNR adapted its management to include pre-emergent herbicide applications, to slow the invasives down, and broadcast seeding, to give the natives a headstart. Their approach exemplifies a truth the curators of our future forests must embrace: long-term stewardship of forest succession hinges upon a willingness to reassess strategy and implement revised practices over time.
Do not fight nature; adapt.
When a tree falls, and long thereafter, it makes an uncertain sound. It is the sound of what was lying in wait underneath the topsoil; it is the sing-song sound of the Eastern towhee who has come to nest in the nascent clearing; it is the thrumming sound of the piliated woodpecker who has mature forest into which they may retreat.
Whether that sound is ultimately hopeful or dreadful depends upon the confluence of all these and more; but most influential and yet most uncertain of all is the power we wield as interlopers and to what extent we will exercise that power for stewardship.
Written by: Ryan Brett, Land Protection Specialist
Sources Cited
Hoover JP, Brittingham, MC, and Goodrich, LJ. (1995), Effects of Forest Patch Size on Nesting Success of Wood Thrushes, The Auk, Volume 112, Issue 1, 1 January 1995, Pages 146–155, https://doi.org/10.2307/4088774
Mech SG and Osgood D. (2020). Ecosystem Response to Forest Management Practices in Nolde Forest. PowerPoint Session Presented at Albright College Department of Biology, Reading PA.
Metz R and Osgood D. (2014). Grab Your Pitchforks and Torches: The Variables that Resist Invasive Species Within a Disturbed Community. Albright College Department of Biology. Research Paper Presented at Albright College Department of Biology, Reading PA.
Rhemtulla, JM, Mladenoff DJ, and Clayton MK. (2009). Legacies of historical land use on regional forest composition and structure in Wisconsin, USA (mid-1800s–1930s–2000s). Ecological Applications, 19: 1061-1078. https://doi.org/10.1890/08-1453.1