Interfering Vegetation Control in Thinned Woodlots and Silvopastures

Most of us know all too well how increased solar energy at the ground level following a thinning = increased understory growth - for better or for worse!  Whether the management objective is long-term timber or silvopasture management, too much of the wrong plants in the understory can really interfere with management objectives (thus, the term "interfering vegetation").  As I've walked around the farm during hunting season, all of the little "unwanted" plants seem to stick out like a sore thumb and serves as a strong reminder of how challenging it is to feasibly manage plant communities in forest ecosystems and silvopastures. 

One of our Cornell Master Forest Owner volunteers from Dutchess County in SE NY emailed me the following question.  There's not one right, nor easy answer to this situation, so I'd like to open it up for others to comment:

From Greg: "I need some coaching and guidance on fern control. As I apply TSI and crop tree release cuts, I am starting to see excessive growth of ferns and other undesirables like striped maple. Luckily I have not seen a lot of barberry, multi-flora, or euonymus; at least not yet.  How do you recommend managing them. Most of my forest is outcrop rocky with slopes. Bush hog or other mechanical control will be challenging."

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I agree that there isn't a single 'right' or easy answer to this question.  Whether it is ferns, striped maple, beech or the long list of invasives, 'interfering vegetation' is a major issue when trying to obtain adequate desirable regeneration of native trees and shrubs.  As I look back at woodlots I have had harvests carried out over the last almost 30 years I find myself asking the same questions [and pretty frequently lately] - why didn't we get better regeneration?  What should we have done differently? What can we do now? How are we going to deal with the 'beech thickets"? How do we deal with the 'interferers'?  We are doing some herbicide treatment of beech and invasives but not enough.  I have been thinking a lot lately while wandering in the woods that more under planting whether bare root seedlings or direct seeding may be needed to begin to get more desirable results.  Personally I think this is one of the greatest benefits of implementing a silvopasture practice to control unwanted vegetation.  I think Pete had a webinar on regeneration issues last year. 

Silviculture legend Dr. Nyland from ESF did a day-long training last in July for the Society of American Foresters on the challenges of obtaining successful natural regeneration in forest stands.  Some of the comments he made that day that have stuck in my mind, and which are relevant to this discussion:

  1. deal with little problems before they become big ones.  Don't think that those little innocuous striped maple, ferns, etc. in the understory will remain so innocuous once they get an extra dose of sunlight.
  2. Different problematic plants have different threshold levels which would trigger the need for control - and these levels vary from situation to situation
  3. successful regeneration requires risk management through integrative thinking
  4. Silviculture = establishing and maintaining healthy communities of trees AND other vegetation that have value to people.  I suppose that the same could be said for silvopasturing (+ livestock)
  5. Silviculture involves deliberately controlling the process to achieve a desirable outcome (again, same thing could be said for silvopasturing)

The most viable control method is going to change from one plant species to another, as well as one stand to another.  And of course, management objectives, resources and numerous other factors also come into play when trying to decide just how to reduce unwanted plants.  It seems to me that we can spend a lot of time, money and energy reacting to "bad" plants and vegetative conditions in our woods without making much headway towards improving the mid-to-long-term situation (the "Band-Aid" syndrome)  One of my personal interests for silvopasturing is to reduce and manage the quantity and development of noxious plants in disturbed woodlots and plantations until which point it becomes necessary or appropriate to start the regeneration process (by "disturbed", I mean both bad and good - such as a well-thinned stand with increased sunlight at the ground level)   On our farm (and throughout much of upstate NY) I would estimate that the average age of our woods is ~ 80 years.  At that age, the better trees are still growing well and have decades of vitality before I have to worry about replacing them and carrying on their genetics.  But in the meantime I need to keep thinning our woods to keep the best trees growing better, and to harvest the firewood and timber that we use.  Each time I cut a tree, I'm letting sunlight in, which in turn stimulates "stuff" to grow in the understory.  I've come to realize that at least in our own situation, it makes more sense to use controlled livestock grazing to add value to some of that stuff - and shift the composition to something that I can manage more readily when the time comes to think about regeneration.  I'd much rather deal with a stand of grass and herbaceous plants in the understory (all the while providing quality grazing to our animals and the wildlife) than a heavy understory of shade-tolerant, thorny, hard-to-kill brush.   But regardless of the age of the stand, regeneration isn't even an option until I've dealt with the interfering vegetation.

From what I have been seeing in Central NY/ Southern Tier, we need to change from a reactive to proactive management style. We need to plan for and manage for regeneration today rather than down the road. The invasive seed inventory (spore stock w/ ferns) is well established, and an over-abundant deer herd is actively browsing. Every time we open the canopy, we should also be actively controlling what is going to taking advantage of the released light and nutrients available. Nature is designed to keep the ground covered with growing plants. While there tends to be some resistance  (by many landowners, especially those who live in the city and these woodlots are country getaways) to herbicide use, controlling what is growing is more important than ever. I think it is never too early to select a few saplings, or plant a few and providing some type of deer protection such as tree tubes may be a necessity despite the added labor and management associated. Even in our younger forests, a significant wind or ice event might devastate the upper canopy and it would be nice to have the next crop ready to grow. I don't think we should be afraid to seed cover crops into our forests as well. Even if livestock are not a mixture in the management plan (which would be ideal--- if the management is there), Keeping the ground covered with growing plants is nature's intent, and may be an effective way to put a check on invasive regeneration as well as keeping the ground temperature cooler which is also important for the forest ecosystem, and becoming an issue thanks to another invasive, the earthworm---a whole other story.

Well said, Karl.  For landowners that have the option of raising livestock, there is a decision to be made on whether to grow firewood or forages; noxious brush or understory plants that have value; postpone the inevitable (the eventual expensive and difficult control of an interfering understory) or the cost-effective transitioning of understory conditions to a state that will make natural regeneration a viable option when the time comes.

If we look around the landscape at many of our farm woodlots, it's apparent that the silvicultural cycle of a healthy woods is broken.  Silvopasturing offers the potential to generate profit from this land AND at the same time restore healthier conditions, present and future.

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