Eastern National Parks: Forest Regeneration Failing in 69%

Gettysburg battlefield; now under attack by emerald ash borer (from Faith Campbell’s blog post)We don’t often talk about the Eastern forests, but Faith Campbell has an interesting post about regen in eastern National Parks.  Faith examines and puts in context a paper by Kathryn Miller and colleagues.

Kathryn Miller and colleagues (full citation at end of blog) have published a study that examined the status and trends of forest regeneration in 39 National parks from Virginia to Maine. Four-fifths of the forest plots in the study are classified as mature or late successional – so at first glance the forests look healthy. However, the researchers made an alarming finding: in 27 of 39 parks, forest regeneration is failing – either imminently or probably. Acadia National Park is an exception; it is the only park in the study experiencing healthy regeneration. They warn that without intense, sustained – and expensive! – intervention, these forests are likely to be converted to other types of ecosystems. [I  blogged recently about findings regarding regeneration in eastern forests: here  and  here  and here and here.

The forests’ understories have too few seedlings and – especially – saplings to maintain themselves. Worse, in many cases the seedlings and saplings are not the same species as the mature trees that form the canopy. The saplings are shorter species that never reach the canopy. That is, species like pawpaw (Asimina triloba), American holly (Ilex opaca), American hornbeam (Carpinus caroliniana), and eastern redbud (Cercis canadensis) are regenerating, rather than the oaks (Quercus spp.), hickories (Carya spp.), maples (Acer spp.), and pines (Pinus spp.) that constitute the canopies of mature forests in these parks.

It sounds like species that do well growing in understories are doing well, and species that need light and bare mineral soil to become established are not doing so well.    In many places in New England, stands regenerated post-agricultural clearing.  If you want certain species, it seems like you may have to manage to get them back.  But this paper seems to imply the interesting idea that “what used to be there” is what should go back… even though “what used to be there” might just be an artifact of the stand history.. and influenced by non-Indigenous  as well as Indigenous residents of these landscapes.

Miller and colleagues call these “regeneration mismatches.” In about half of the parks, these native canopy tree species make up less than half of current saplings and seedlings. This situation suggests the forests’ species composition will shift substantially, thereby undermining resilience in the face of other challenges, such as invasive plants and pests and climate change.

I think the idea that any shifts will ipso facto undermine resilience is questionable.  A few concepts to consider: invasive species have been a separate problem from climate change (that is, climate change in the current anthropogenic global warming sense).  One can imagine that invasive species could do better (or worse) as the climate changes (whether due to human or other factors).  We can also imagine that invasive species could make ecosystems more or less resilient to climate change.. depending on how you define resilience (some green stuff covering the soil? specific species in specific places they used to be?).

Let’s think about a western situation, say, there’s a great deal more true fir than ponderosa pine regen without intervention.  If a forest went to true fir,  would it be by definition less resilient to invasive plants, pests and climate change?  Now with true fir, we have a good history of their tendencies to succumb to native diseases and insects, and we think conditions will get drier due to climate change, and they won’t like that. In fact, there wouldn’t be so many of them around except for fire suppression and in some places the removal of overstory pine.

Of course, in the East, deer and invasive plants are also a problem.

Many of the parks experiencing the most severe impacts of chronic deer browse also have the highest invasions by non-native plants. A natural process of regeneration occurs when the death or collapse of mature trees create gaps in the forest canopy. Where deer and invasive shrubs overlap, this process is often hijacked. Instead of nearby native tree species accelerating their growth toward the canopy, thickets of invasive shrubs crowd the space.

For this reason, Miller and colleagues recommend that park management prioritize treating invasive plants in canopy gaps of disturbed stands to avoid forest loss. They recommend deliberate creation of canopy gaps to promote resilience only for parks, or stands within parks, that have low deer and invasive plant abundance or the capacity to intensively manage invasive plants in gaps.


The authors also recommend actions to open the canopy or subcanopy to facilitate growth of saplings belonging to desired species. They caution that deer predation must be controlled. Furthermore, either invasive plant cover must be low, or management must ensure that that the park has sufficient resources to sustain an invasive plant control program – especially if invasive plants are combined with abundant deer.

Parks experiencing compositional mismatches and that are dominated by oak–hickory forest types might also benefit from prescribed burning. Again, deer browse pressure must be minimized. In addition, regeneration of oaks and hickories must already be present.

It seems like they are saying “if you want early successional species, you need openings (plus protection from deer)”- seems like “leaving mature and old growth alone” as a strategy may have unintended (albeit predicted, based on forest ecological knowledge from the 1970’s) negative consequences.

18 thoughts on “Eastern National Parks: Forest Regeneration Failing in 69%”

  1. Once again, thinning and prescribed fire look like(as in most cases) to be the solution.
    Thinning(including some commercial) can improve forest heterogeneity(stand diversity in type, size and spacing). Which is the problem being cited by this article/study.
    Prescribed Fire(as most of us know by now) can keep invasives at bay and be low impact management tool.

    • Well, some would consider small openings, large enough for early successional species, to not be “thinnings” but rather “clearcuts”. So language can be a roadblock to understanding.

      • You are absolutely right. Many people think that a clearcut is when you cut more than a few trees standing next to each other, when in reality that’s an emotional assumption.
        A clearcut is a forestry prescription used to maximize timber production, and a Forester would never call a clearing of 3 acres or smaller a clearcut because it wouldn’t meet the objectives of the clearcut prescription. Whereas small clearings in the forest provide habitat for both plants and animals that would otherwise be non-existent in a fully enclosed forest. Many forest ecologists, myself included, prescribe small clearings in order to improve the over all forest health.
        Public Perception is probably the biggest barrier. Many folks believe that the land Europeans came to was untouched when in fact nearly all the land we currently manage and live on existed in a condition that was influenced by Indigenous peoples management of the land for many thousands of years.

        • Many thinning projects could contain a few up to 5 acre ‘clearcuts’. If a timbermarker runs across a piece of ground that doesn’t really have viable leave trees, a patch cut could be made, with a note to the reforestation people, for replanting. It’s not often used, as it takes a keen eye to see those while you do your job. Inexperienced markers should not be making those decisions.

          Additionally, the “gaps and clumps” ideas have gained some acceptance in forest management. I’ve done a lot of that, in the “clumps” category. It’s harder to justify making openings bigger, while still following the rules, laws and policies embedded within the marking prescription.

  2. I agree that “any shifts will ipso facto undermine resilience” is questionable. If we are not artificially driving those shifts, I think they are likely to result in conditions that are more resilient.

    I don’t necessarily see protection from deer and removal of invasive species (or prescribed burning) as incompatible with “leaving mature and old growth alone.” I think strategies that prioritize mitigation of the consequences of human interference and artificial conditions will tend to promote resilience. (I’m assuming deer are outside of their range of natural variation because of something we’ve done.)

    • Ah but what is “human interference” and “artificial conditions”? Does Indigenous burning count as “human interference”? Does not allowing the same kinds of burning as Indigenous people did, in its turn, be “human interference” with other humans? Since humans have been on the landscape in North America since glaciation, apparently nature has been quite resilient so far or maybe not?
      It seems to me that groups of plants and animals are always changing on the landscape.. and we can’t get away from deciding which ones we want and don’t want so much of and what to do about it. If we decide we want to return to pre-Columbian landscapes without Indigenous people with those pre-Columbian practices intact, I think we are in for a world of practical and philosophical difficulties.

      • I have found the “native burning” argument to be a distraction. If burning was part of what made a forest resilient in the past, then there’s no a priori reason that it shouldn’t be part of its future. I don’t think we have to spend a lot of time figuring out what share of the burning was human-caused historically. I’m more inclined to think that suppression of fires created artificial conditions in many places.

        • OK then, if a certain set of circumstances, human-caused or not, made previous forests “resilient” what are those characteristics of the forest specifically? Apparently some species can not be resilient, say to introduced stressors, a la Chestnut, and yet different species are now there.. “the forest” appears to be resilient.

          • The Planning Handbook discusses circumstances where historic conditions may not be possible, which would fit this situation, and principles to apply in such situations. Maybe that means new conditions that have adapted to the area on their own are resilient, but there is a lot more uncertainty associated with conditions that have been there less than a century, which should be reflected and explained in relation to the chosen management strategy.

            I took a quick look at the Nantahala-Pisgah revision planning documents. The Assessment describes the changes since chestnuts were killed off. This is from the Record of Decision:

            “Overall, in Western North Carolina, ecosystem characteristics dominant in historic times are different today (such as the loss of American chestnut, decline of Fraser fir and eastern hemlock from insect pests, change in fire regimes, hydrology etc.), therefore it is appropriate to consider other approaches beyond NRV, and this was done in the planning process…”

            How “this was done in the planning process” to come up with desired conditions looks like it would take a little digging, but maybe someone involved could explain how they determined NRV/resiliency/sustainability where the dominant historic tree species is gone. (There is a guideline and “management approaches” that reference possible restoration measures for chestnuts, but I don’t think that’s part of their desired condition.)

            One other thing that interested me was the failure to mention chestnuts in the “Ecological Sustainability Analysis” appendix to the FEIS. I would have thought that it would have been a key discussion item for some of the species that used to rely on it to talk about how they have since adapted to remain viable.

            Also of note – there has evidently been a setback in the genetic engineering of blight-resistant American chestnuts: https://www.syracuse.com/outdoors/2024/01/lab-mixup-muddies-federal-approval-for-esfs-experimental-new-american-chestnut-trees.html?outputType=amp
            (There also seems to be vocal opposition, maybe to release of genetically modified products generally, that portrays this as a fatal flaw.)

  3. Over 100 years ago, chestnut blight dramatically changed the Eastern Hardwood forests. Chestnut was a predominant tree that was practically eliminated. Also, dramatic overharvesting in the late 1800’s and early 1900’s changed the forests. That is how the Weeks Act came about and why we now have National Forests in the East.

    Oak and hickory are usually the desired species and when they become mature and closed canopy, it creates conditions for shade tolerant species to establish in the understory. Oak seedlings usually do not do well in those conditions, rather red maple and less desirable species establish. Oak is usually desired for lumber but also as a mast producer for wildlife. Coppice reproduction through shoots or suckering is the common way to regenerate oak. Obviously to do this, trees have to be cut down. This can be done through group selection cuts with small openings throughout the stand and using uneven-aged management.

    If there are some oak seedlings present in the understory, they usually are outcompeted by red maple and other species, at least initially. To address that, repeated prescribed burning will top kill the oak, but allow its root system to spread and it will resprout after each burn. This is done so that over time, with its advanced root system, it can outcompete some of the other species that do not survive repeated burning like oak does.

    Oak systems have evolved with fire and the removal of fire is one of the reasons that they are having difficulties with oak regeneration.

    • “Obviously to do this, trees have to be cut down.” Not obvious to me, wondering how they survived before axes and saws.

      • Well, I was referencing coppice reproduction. In order for this to happen, generally something has to happen to the existing tree. For instance, if you are more familiar with aspen, when you have a mature aspen stand, often there are not a lot of young aspen in the understory (but there can be, depending on the development of the stand). When the mature aspen are cut, or they could also be blown down or even burned, there is usually a flush of new growth from the stump or roots. When mature aspen die off from old age, they usually have lost some of their ability for coppice reproduction.

        • While in Grand Canyon National Park, at the north rim, I saw where a wildfire had burned at high intensity, a few years before. All the pines were dead, and I didn’t see any natural pine regen. I did see tons of aspen coming up, though. The aspen might end up ‘shading-out’ any pine volunteers, away from the fire’s edge.

        • I visited the big Wallow Fire (2011) near Alpine AZ last summer… it was a HOT one!! But the flush of aspen throughout the area was stunning. Driving through the gorgeous Dolores River valley (San Juan NF) and it’s stunning aspen stands reminds me that it, too, was “devastated” decades ago. I believe you have your own story of an escaped Rx burn on the Kaibab NF??

          • It was the Warm Fire in 2006 on the North Kaibab. I went back there a couple of summers ago and the aspen growth across much of the fire is really incredible. I don’t know this for a fact, but I have to believe it is now one of the largest aspen stands in the country. Aspen is a pioneer species and nature is doing its thing there. I was relieved to see what it looks like now.

          • Often Coloradans drive through the footprint of the Hayman fire. Lots of aspen regen but not so much pine.. mostly still grass fields; not “destroyed” but not forested either.

      • Well, there must have been openings at some point in the past or species like oaks would not have gotten established. Were the openings due to firewood cutting, clearing for farming, fires or ??? We’d have to go back and look.

        Which takes us to today.. how would openings be created? By hurricanes or other wind disturbances, fires, or human tree-cutting for wood products or for the sole purpose of tree species biodiversity and wildlife early successional habitat?

  4. I recall that Allegheny NF (w highly valuable black cherry) decades ago instituted fencing of logged units (based on FS research) and drove deer out, excluding them for about 5 years to allow regen to establish and grow beyond browse risk before removing fencing. This proved wildly successful. Overpopulation of deer is ubiquitous throughout eastern forests and hugely impactful to young trees and diversity.


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