[MAIPC] how to get rid of invasive plant debris

Tue Apr 14 10:53:04 PDT 2015

Hello  Maipc members, especially the people who responded to my questions.
Hello volunteer worker

Everything depends on the site, but I copy Dr. Cynthis Huebner who
explained thoroughly what the best and the not so good approach is on how
to prevent invasive plant chemicals to linger in the forest floor. THE BEST
IS TO REMOVE EVERYTHING! This is not always possible, I realize.

Allelopathy as in tree of heaven, bush honeysuckle, and garlic mustard :
take this debris out.

Change of pH and nitrification of the soil from the quick decomposing of
Japanese barberry: take this debris out.

(Take roots out, unless you are cutting the shrub down three times a year
 for a few years. Just two times in total will not weaken the multiflora
rose enough and it will give the roots a chance to get many times bigger.
This is my personal observation.
It did not work on Japanese knotweed (We cut one patch 5 times in one
season,
by cutting every individual stem;  they were somewhat smaller but very
healthy and as abundant the next year. Pia)

Hello Pia,

  Generally, it is not a good idea to leave invasive plants behind because
some (not all and not most) do exude allelopathic chemicals.   These would
include garlic mustard, some bush honeysuckle (perhaps all), and tree of
heaven.  Many invasive plants also tend to be very high in nitrogen and
other nutrients.  Depending on the site, this could be good or bad.  If the
site is naturally composed of a low-fertility rather acidic soil, adding
nutrients can change the soil composition, which may over time influence
the types of plants that can grow there.  If the site was originally
composed of more acidic type plants (i.e,, blue berries), then they will
have trouble regenerating in a  more alkaline soil.  Such fertile soils are
highly susceptible to reinvasion from nearby propagule sources.

  If you have no choice but to leave the plants, I would advise piling them
in one area or the fewer the piles the better – keeping the area as small
as possible, while the pile may become quite tall.  Spreading the piles
around may actually spread the impact further.   While the one or few piles
may negatively affect the area it is in, its overall impact is likely to be
less.    If at all possible, I would remove as many piles as possible  --
at least to a non-wooded location, perhaps the forest edge.  You are right
that doing so will allow for more regeneration.

Hi Pia

  Hanging the invasive species debris above the ground or putting it on
piles of wood/rocks may be an option that will slow the leaching of
nutrients and/or allelochemicals to the soil.  There will still be runoff
but it is possible the sun or just time could break down some of the
chemicals before they reach the soil.  Again, if you can remove them
completely, this is the best option.

  There is some weak documentation of allelopathic behavior for ligustrum,
but it may depend on site characteristics and the species involved (see
abstract of a student’s dissertation bellows).  There is no documented
allelopathy  yet for Japanese barberry (at least that I am aware of yet).
Japanese barberry does change the soil (increases nitrification and pH)
around it via rapid leaf decomposition.  However, if you think you are
seeing an allelopathic effect, it should be evaluated.  It may be that your
site conditions are conducive to the release of the allelopathic chemicals
or the plants in your area are more likely to be impacted by any that are
present.

“Allelopathy occurs when a plant species releases allelochemicals into the
soil that impact the germination, survival, or growth of that species or
neighboring species. Soil microbes can increase or decrease the effect of
these chemicals, but few studies have determined whether soil microbial
effects are predictable across different plant species. Plant-soil feedback
occurs when a plant species changes the soil microbial community in ways
that affect the growth or reproduction of that species or neighboring
species. Allelopathy and plant-soil feedback are two mechanisms that might
explain how invasive plants impact native plant communities and come to
dominate local habitats. Both of these mechanisms have the potential for
legacy effects on the soil and plant communities after the invasive has
been removed. We tested whether three local invasive shrub species of the
eastern deciduous forest (*Lonicera maackii, Ligustrum vulgare*, and *Elaeagnus
umbellata*) have allelopathic effects on each other or any of nine native
plant species. Our results were complex and involved many interactions.
Overall, we found that the allelopathic impacts of the invasive species
changed depending on the soil microbial community, the seedling species
being tested, and the growth stage of the seedling. We also tested whether
the same three invasive shrub species, and the invasive woodland
grass, *Microstegium
vimineum*, participated in plant-soil feedback with native species. We
found evidence that all four invasive species affect aspects of the soil
microbial community and that these soil microbial effects can change with
time and competitive context. We also found evidence for legacy effects on
some components of the microbial community (e.g. mycorrhizal fungi). We did
not find strong evidence that these microbial effects resulted in feedback
dynamics that promote the dominance of these invasive species.

Synthesis: The effects of invasive plants can interact with the abiotic and
biotic environment in complex ways. Future studies should incorporate the
effects of these biotic and abiotic factors in their experimental design.
We also found that these interactions can change over time and in different
biotic and abiotic contexts, suggesting the value of long-term studies of
these interactions and the need to unravel their context dependency in
order to assess their ultimate role in driving plant community structure
and dynamics. “

  If you wish to share my comments that is fine.  Please keep in mind every
site is different and what has worked at one site may not be the best
solution for all sites.   Management is site-specific.

Cindy

[image: Forest Service Shield]

*Cynthia D. Huebner, PhD Research Botanist*

*Forest Service*

*Northern Research Station*

Ecology and Management of Invasive Species and Forest Ecosystems

*p: 304-285-1582 <304-285-1582> f: 304-285-1505
<304-285-1505> chuebner at fs.fed.us <chuebner at fs.fed.us>*

180 Canfield St.
Morgantown, WV 26505
www.fs.fed.us

http://nrs.fs.fed.us/people/chuebner

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*Caring for the land and serving people*

*From:* Pia van de Venne [mailto:pia.parkprotector at gmail.com]
*Sent:* Monday, April 13, 2015 9:36 PM
*To:* Huebner, Cynthia D -FS
*Subject:* Re: questions about invasive plant removal

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