[MAIPC] A conjecture on invasive vines and tree falls

[frazmo]

I appreciate the feedback on my invasive vines and treefalls post. And I
agree with the points Jil makes about English Ivy directly damaging trees.
In addition to what Jil mentions, from my own observations over many years
and hundreds of trees, dense ivy growth around the base of a tree creates a
microclimate conducive to harm: shady, moist, and lacking in airflow. I
tend to find rotting bark under the ivy if it had been there for some time.
That microclimate must facilitate the introduction of fungal and bacterial
pathogens, and possibly insect attack also. In my personal volunteer work,I
try to remove the ivy at the immediate base of the tree as much as I can
while conscious ot trying to avoid creating further damage. Sometimes I see
the tree trying to heal itself from the damage; sometimes not. I have taken
many photographs showing the kind of damage I am talking about. So ivy can
cause gross damage and weaken trees as Jil discusses and I'm elaborating
upon. In speaking of "ghost impacts" I am thinking about more subtle
effects that would be underground, out of sight even when the ivy is gone.

Again, thanks for the discussion and ideas. Cheers,  Steve Young, Arlington

On Thu, Mar 22, 2018 at 9:21 AM, Jil Swearingen <jilswearingen at gmail.com>
wrote:

> In addition to Steve's suggested "ghost impacts," I'll offer more
> conjecturing.
>
> Based on personal observations over the past several decades, that are
> not backed up by hard science, I have watched trees heavily covered with
> English ivy vines deteriorate over time, lose most of their branches and
> structure and then die. At some point, even if vines are cut and killed at
> the base, it is too late to rescue a smothered tree. The tree is too weak
> to recover. Physically, the heavy growth and dense foliage (mini umbrellas)
> of English ivy blocks sunlight for the host tree foliage, leads to reduced
> photosynthesis and growth in the host tree, reduced water availability for
> the host tree (the vines get most of the water that would otherwise be
> available to the tree), and the vines probably cause some level of damage
> to the bark which could lead to increased vulnerability to insect pests and
> pathogens.
>
> We have identified lots of factors to be studied. Now we just need someone
> to do the research.
>
> Jil
>
> Jil Swearingen
> Invasive Species Consultant
> *In the Weeds*
>
>
>
> On Wed, Mar 21, 2018 at 9:27 PM, Ruth Douglas <cvilleruth at embarqmail.com>
> wrote:
>
>> I’m going to try to contact someone in VDOT (Va. Dept. of Transportation)
>> and someone at Virginia Power to see if anyone there is looking at the role
>> of invasive vines in trees down in storms.
>>
>>
>>
>> Ruth Douglas
>>
>> Invasive Plant Educator, VNPS
>>
>>
>>
>> *From:* MAIPC [mailto:maipc-bounces at lists.maipc.org] *On Behalf Of *Nathan
>> Hartshorne
>> *Sent:* Wednesday, March 21, 2018 6:41 PM
>> *To:* frazmo
>> *Cc:* MAIPC Listserve (maipc at lists.maipc.org)
>> *Subject:* Re: [MAIPC] A conjecture on invasive vines and tree falls
>>
>>
>>
>> Perhaps the previous ivy spread had stopped development of an understory
>> that would have helped prevent windthrow since the gaps in a forest can
>> help facilitate it.
>>
>>
>>
>> On Wed, Mar 21, 2018 at 5:32 PM, frazmo <frazmo at gmail.com> wrote:
>>
>> Continuing from the recent thread, it seems intuitively obvious that the
>> weight and windload burden of invasive vine growth would cause mature trees
>> to be more vulnerable to high winds. But I also conjecture that non-native
>> invasive vines may have "ghost" impacts even when they have been removed.
>> Based on personal observations at Long Branch Nature Center in Arlington
>> VA, we have lost dozens of mature trees due to wind storms from Hurricane
>> Isabel (2003) to now. My sense is that a disproportionate fraction fell in
>> areas that had been heavily blanketed in English Ivy growth circa pre-2004.
>>
>> Even though the ivy had been removed, the trees fell. The conjecture is
>> that the invasives' growth had altered soil characteristics and tree root
>> growth patterns in ways that left the trees more vulnerable going forward.
>>
>> I agree that this whole area seems like a great topic for research and
>> this is just one more angle to consider. Cheers,
>>
>> Steve Young, volunteer, Arlington VA
>>
>>
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>
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