Are Oaks In Trouble?

[Music] greetings everyone I'm Adam Haron today I want to talk about something remarkable that isn't obvious to a lot of people even to those of us who spend a lot of time in the woods but it's happening right now all around me if you look closely so right now I'm hanging out in a beautiful wooded area in Western Pennsylvania when we take a look around and especially up we see that the dominant trees in this Forest are Oaks in the querkus genus and these Oaks appear to be healthy I would say that most of the dominant Oaks here are at least 75 years old some of the larger ones I'd say are almost certainly over a 100 years old now let's focus our attention further down and let's look at the sub canopy layers when we do that we see something interesting and I would even go so far as to say we can see into the future and here is where ecologists detect a problem ecologists are pointing out that in mature Oak forests specifically in the eastern and Mid-Atlantic regions of the United States Oaks are mostly absent from the sapling and midstory size classes what this means is that when the largest Oaks die other trees that aren't Oaks will fill in those gaps and eventually dominate the overstory in other words this maturing Oak Forest will cease to be an oak forest in the future unless something changes now it's important to recognize that this problem isn't just a local phenomenon according to ecologist Daniel Day failure to regenerate Oak forests is a worldwide phenomenon the name of this ecologically important issue is appropriately titled the oak regeneration problem and as I pointed out we see it happening here the dominant overstory trees all around me in this Forest are mostly Oaks including northern red oak Black Oak Scarlet Oak White Oak and Chestnut Oak we also see a few mature hickories in the over story specifically shag bark Hickory and Pig nuts Hickory when we look below the overstory trees specifically near the ground level we do see some Oak seedlings Oak seedlings aren't uncommon in many Eastern forests particularly following years of heavy Acorn production and you might predict that in the future these seedlings will replace the mature Oaks but according to ecologist Mark Abrams Oaks are still being successionally replaced by other species despite observations that many forests contain a substantial number of Oak seedlings the oak regeneration problem persists because what we generally don't see in many mature Oak forests today is a sufficient number of Oaks in the mid story so we don't see a lot of Young Oak Oaks that are beyond the seedling stage and maybe beyond the sapling stage we see Red Maple in the under story and midstory we see American Beach we see tulip tree we see black cherry we see sugar maple these are the trees that are likely to dominate the upper canopy when the large Oaks eventually die now is this really a problem I mean isn't any Forest here better than no Forest at all and isn't the replacement of Oaks by other trees just Nature's Way of responding to predictable environmental cues well it is a problem according to many ecologists who consider Oaks to be Foundation species whose acorns feed many species of wildlife whose root systems connect with micro risal fungi and whose leaves and bark and other structures host incredible invertebrate communities that feed many birds and other animals so why is this happening why are Oaks fairly abundant as large canopy trees and many Midwestern and Eastern forests but less prolific in the sapling and midstory size classes well to answer that question we have to understand the recent history of Oaks in this region following the last glaciation so let's say 10,000 years ago to within the past few centuries Oaks increased in dominance in many areas of the Eastern United States largely because the climate was favorable and periodic low to moderate intensity surface fires were common these fires were initiated by humans intentionally and unintentionally and by lightning even after European settlement fires continued to burn periodically in many areas and Oaks responded very favorably to these conditions because many Oaks are fire adapted trees they generally have thick bark they are able to resprout prolifically and they tolerate drought but fire wasn't the only factor that favored the growth of Oaks particularly in the past 150 years selective logging the demise of American chestnut agricultural land abandonment and a reduction in the number of browsing animals also favored the growth of Oaks now something interesting happened early in the 20th century fire suppression became a common policy initially this practice benefited Oaks that were already established but as the decades progressed people started noticing that Oaks weren't regenerating as successfully as they once did and eventually most ecologists pointed to fire suppression as the main contributing factor responsible for the absence of Oaks from the sapling and midstory size classes now of course other factors like disease Rising deer numbers and insect infestation from organisms like gy Ipsy moth which is now referred to as spongy moth all affect the success and health of Oaks but without fire the understories of mature Oak forests become quite dark and without adequate light levels Oaks struggle to thrive compared to many other trees Oaks are typically less shade tolerant and they can easily be outcompeted by other trees that grow well in these low light conditions now there's a term that ecologists use to describe what's going on today day in these forests where Oaks are failing to regenerate successfully and that term is mesophication or mesophication if you've watched some of my recent videos you've probably heard me use the word mesic or mesopic when talking about trees and forests mzik or misic means a moderate amount of moisture and a mesopic forest is a forest whose species are adapted to growing in moderate amounts of moisture massification refers to the conversion of a non- mesopic forest into a mesopic forest in our case we're talking about a conversion of a pyrotic forest or a forest whose plants are adapted to fire into a mesopic forest ecologists who talk about mesopic talk about the massification hypothesis which suggests that the absence of fire in a fire adapted Forest favors the growth of shade tolerant fire sensitive species in the under story and midstory these mesophytes create shadier cooler wetter conditions in the under story further contributing to the growth of mesopic species all while inhibiting successful regeneration of Oaks and other fire adapted species and that's exactly what's going on here yes there are some Oak seedlings that sprouted in the past few years yes there are plenty of mature or maturing 75 to 100y Old Oaks some even older that are thriving in the upper canop of this forest and because Oaks are long lived trees these large Oaks will likely continue to dominate the upper canopy for many years to come maybe for another Century maybe two but when these large Oaks die who is going to take their place other Oaks probably not in this Forest because the oak seedlings that exist here today will probably perish within a few years due to the low light conditions and there probably won't be enough Oaks in the sapling and midstory size classes to recruit to the overstory instead mzik species including Red Maple and tulip tree will likely dominate the overstory of this forest in the future now even though this situation spans large areas of the United States there are some exceptions to what I've just outlined mesopic is most likely to occur on what are called productive or quality sites so sites whose soils are moist rich and fertile but on dry sites where soils are relatively nutrient poor but still able to support the growth of Oaks successful Oak regeneration from the midstory to the overstory is often successful you can see that this is the case if you've ever walked through a dry Upland area dominated by Oaks and maybe Pines especially in areas where Chestnut Oaks grow on dry slopes and ridges you'll often see Chestnut Oaks and other Oaks in the seedling sapling and midstory size classes and these smaller Oaks on these zerich sites are likely to make their way to the upper canopy when the large Oaks die also generally speaking massification is predicted to occur more quickly in forests dominated by members of the red oak group because trees in the red oak group generally don't live as long as those in the white oak group they are generally less shade tolerant and are less likely to thrive as younger trees in the understory and they are more susceptible than members of the White Oak group to mortality from a disease known as Oak decline now you might be wondering what can be done about this well it looks like fire is necessary or at least extremely important to prevent massification from occurring but fire alone might not be enough but it can be in some situations so it seems as if there are many nuances to the solution at least according to the research it seems that a combination of repeated Burns and some kind of selective clearing of overstory trees followed by firef free intervals can support successful recruitment of Oaks it also seems that in order for Oak forests to continue regenerating themselves plenty of younger Oaks have to exist in the understory and midstory layers before fire and clearing are implemented otherwise major disturbance events will favor fast growing mesopic species particularly on the more productive sites ultimately what ecologists are saying is that without active management many of the mature Oak forests that exist today in the Mid-Atlantic and Eastern United States are likely to undergo massification and eventually become dominated by Maples and other fire sensitive species again is this a big problem or is this just Nature's Way of ebbing and flowing through time supporting the growth of certain organisms for a while restricting the growth of others for a while letting some live letting some die I'm not sure I have any good answers for you but I do know that messic is taking place in my neck of the woods and I like to point it out to people from time to time thank you for watching this video If you enjoyed it I encourage you to check out a brand new online course that I just finished creating it's called exploring wild ecosystems and it highlights ecological concepts like the successional processes that we discussed in this video if you are interested in learning more about the effects of fire on the landscape or how various organisms come together to build thriving ecosystems check out exploring wild ecosystems by visiting learn your land.com and clicking on exploring wild ecosystems to learn more thank you again for watching this video I will see you on the next one [Music] oh [Applause] [Music]

Channel: Learn Your Land

Views: 115,756

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Id: NRWHHOAf39U

Length: 12min 35sec (755 seconds)

Published: Wed May 29 2024