- [Dan] I'm Dan Farrell.
I work in the Wildlife Diversity Program
in the Vermont Fish and Wildlife Department.
I spent much of this past summer documenting
state significant examples
of an under-surveyed wetland, natural community type,
northern hardwood seepage forest.
My goal today is to introduce you to this important
and elusive, new community type,
and raise awareness of its characteristics.
I figure after more people experience it,
we can, you'd, earned even more about it.
Northern hardwood seepage forest was recently added
to the state's list of recognized natural community types,
and was introduced to the public in 2019
in the second edition of "Wetland, Woodland, Wildland"
by Liz Thompson, Eric Sorenson, and Bob Zaino.
Very similar community types occur
in New Hampshire and Maine.
It is also called northern hardwood seepage forest
in New Hampshire and hardwood seepage forest in Maine.
Vermont ecologists like Marc Lapin and Brett Engstrom
have observed the type for many years,
but it didn't fit well in the Vermont classification.
Probably because it's not a swamp.
And notice it's called a seepage forest, not a swamp
or a seepage swamp.
In 2017, our understanding
of northern hardwood seepage forest
was increased significantly by the work
of Hannah Phillips that she did for her master's project
for the Ecological Planning Program
at University of Vermont.
On the summer solstice of 2017,
about 20 ecologists and foresters visited seepage forests
in the field.
And we discussed, among other things,
how it differs from swamps,
and also from just regular wet inclusions in upland forests.
This past summer, I surveyed about 15 seepage forests.
Some of them with Everett Marshall and Eric Sorenson,
also of the Wildlife Diversity Program
in the Vermont Fish and Wildlife Department.
Our work was funded by an EPA grant.
And this work, our work, along with Hannah's
and that of other ecologists informs this presentation.
This is a drafty map of most
of the 40 currently known locations
of northern hardwood seepage forests in Vermont.
We think there are more in the northeast,
and at higher elevations,
places where there is more precipitation
and less evapotranspiration than others.
We think that there are roughly
100 state significant occurrences,
but some suspect this estimate is too low.
State significant occurrences are occurrences
of the type that meet certain criteria
of a ranking of landscape condition,
actual condition of the forest, and also size.
But it's important to know
that there are likely many more
than 100 non-state significant occurrences
that are also important and have ecological value.
We are still learning
about northern hardwood seepage forests,
but we know they're important.
Why?
They are very diverse in plant species.
They are wetlands,
although they're usually mapped as uplands.
Now, that is currently,
they rarely appear on wetland maps
because they are hard to detect remotely.
And we will be sharing our work
with the Vermont Wetlands Program
at the Vermont Department of Environmental Conservation.
And it's important to know that they're also doing
their own mapping of these types of forests
in the wetlands program.
They benefit animals.
They provide habitat for several salamanders.
The soil warmed by groundwater in winter means
an early spring thaw,
and food for bears emerging from hibernation.
Moose feed on vegetation,
especially in natural, open portions.
Cool water supplied to streams by these forests
in the heat of summer
create thermal refugia for brook trout
and other fish species.
This will become more important, obviously,
as the climate warms.
And as headwater wetlands,
they can slow runoff and increase flood resilience.
Also important for climate resilience.
Like woodland seeps, they are fed by groundwater,
but they are larger, often much larger.
They're usually on gentle slopes
where the groundwater is prevented from draining
by an impermeable layer,
usually a compacted basal till that has been compressed
between the glacier and the bedrock.
This causes sheet flow of water percolating
horizontally through the soil.
The water has often a high pH
and high nutrient availability.
I found the pH of surface water to be between 6.5 and 7.2
in the sites that I visited.
This seems to be a typical scenario,
the one I just described in general,
but bedrock forms an impermeable layer on some sites
instead of the basal till.
And some do occur on deep muck.
And others are on steep slopes up to 15 degrees.
And we think there are acidic versions,
but even the soil at a site where granite,
a known sort of acidic rock,
or causing acidic soils, forms the impermeable layer,
where the granite forms the impermeable layer,
it had a pH of six.
Somewhat high.
Abundant hummocks mostly created by root balls
from fallen trees create a fine micro topography.
And so the hummocks and dry inclusions
create a mosaic of upland areas within the wetland.
Some drier areas have a closed canopy.
And wetter areas can be quite open.
Soils are usually about five inches of loamy, organic muck,
over another six inches or so of glade, loamy, mineral soil
with a few red models over compacted till,
as shown in the root ball on the right.
I should say that this compacted till
you're seeing in that root ball is quite dense.
And it's very difficult to drive a soil auger through it,
even, very far,
Common soil series are Cabot, Peru and Buckland,
and also Marlow, and have a compacted basal till
as apparent material.
The seepage often forms runs that become the headwaters
of small streams as they merge together,
and deeper channels act like drainage ditches
and create dry areas nearby.
So at the downstream end of the seepage forest,
these channels seem to sort of dry it out.
So variability in canopy cover,
and depth to water table and high pH
and nutrient availability means wetland species,
upland species, nutrient-loving species, shade-loving,
and sun-loving species often occur as side-by-side
or near to one another,
which in turn means high species diversity.
So high habitat diversity means high species richness.
Herbaceous species cover is usually over 90%
in two 20-by-20 meter plots, I counted 57 and 63 species.
A 15-by-20 meter high elevation plot had 54 species.
And I'll add here that these forests
are very pleasant places to visit
on a hot summer day because they are literally cool.
And they have a lot of great plants to look at.
Closed canopy areas are dominated by sugar maple
and yellow birch, with some white ash, black ash,
other northern hardwoods and balsam fir.
Wetter areas are woodlands,
or very open with more black ash.
Some open wet areas are in transition
with many standing, dead trees.
Common wetland plants include northeastern manna grass,
gynandrous sedge, common jewelweed, foamflower,
dwarf raspberry, rough-leaved goldenrod,
purple-stemmed aster, water avens, alderleaf buckthorn,
false hellebore, lady fern, cinnamon fern,
sensitive fern, and rough-stemmed sedge.
Species on hummocks include whorled wood aster,
intermediate woodfern, fall Solomon seal,
bunchberry, and Sarsaparilla.
Nutrient-loving species include silver glade fern,
zigzag goldenrod, blue cohosh, and plantation leave sedge.
Some uncommon species are regularly found,
including long-bracketed green orchid,
and large yellow lady slipper.
Musk flower occurs in the most open, wet parts.
And northern wild licorice is found
at the top of the seepage usually,
right where the right rear it comes out of the ground.
The rare, hairy wood mint,
and the rare to uncommon large toothwort seem
to occur at higher elevations.
Eric Sorenson recently told me that he expects
that the variance ultimately
will reflect Vermont's major forest types,
including northern hardwoods, hemlock, and spruce fir.
And so maybe not oak pine, it seems a little bit too dry,
but you never know.
So the montane seepage forest shown here
is a variant that occurs above about 2,000 feet,
often with open glades and a canopy of yellow birch,
red spruce and balsam fir.
Falls hellebore and mountain woodfern are common.
And northern wild licorice and hairy wood mint
are sometimes present.
Some montane seepage forests
are much more like montane spruce fir forest,
vegetatively, as can be seen here.
And overall, this variant may be more common than we think,
and we have a lot to learn about them.
Black ash seepage woodlands
are dominated by an open canopy of black ash,
and often appear as inclusions in the main type,
with a wetter, flatter surface,
and very dense herbaceous cover.
Hemlock seepage forest is dominated by hemlock.
And I only know of two sites,
and they're both at relatively low elevations.
And maybe they'll be a little further south than most.
Okay, how to find them.
Since they occur on slopes with canopy species
like northern hardwood forest,
northern hardwood seepage forests can be difficult
to find using remote sensing data like aerial photography.
And they are regularly mapped
as upland natural community types.
And as I mentioned, known occurrences are rarely included
on wetland maps.
So, but some datasets do provide clues to their presence,
though gentle slopes below distinct break
with steeper slopes,
which I think you can see here,
especially on Cabot, Peru, Marlow or Buckland soils
are promising, and seepage runs are often apparent
on LIDAR, although not here, at least to me.
And wet canopy openings are visible on aerial photos,
as shown in the black ovals.
But there are no guarantees.
At one site, I found them almost everywhere
with promising topography.
In others, I did not.
And I soon realized I couldn't make assumptions
beyond my sight line.
I often had to walk the boundaries
with my GPS in order to map them.
And in some cases, when they disappeared,
their disappearance seemed to be related
to small bedrock-related topographic features
or increases in slope.
But I suppose if you don't have the groundwater
and the impermeable surface, in some cases,
it just disappears.
So management conditions, considerations.
Northern hardwood seepage forests are fragile.
They're especially hard to detect in winter.
So it's important to delineate them
during the growing season.
Running and compaction from forestry equipment
can create channels that drain them,
or otherwise significantly alter their hydrology.
We think cutting in or uphill of community occurrences has,
in some cases, reduced evapotranspiration enough
to raise the water table,
leading to the die off of trees
and possibly a permanent transition to sedge, cattail,
or alder-dominated wetlands.
An experimental study co-authored by Tony D'Amato
of the Rubenstein School
documented a similar process
in black ash wetlands in Minnesota.
So increased awareness and documentation
of this important natural community type
will foster further understanding and mapping.
And there are many outstanding questions.
How many are there? Where are they?
What is the variation in species composition?
And are there more acidic versions?
So stay tuned.
And it's probably obvious by now
that a lot of people have contributed
to our understanding of this community type.
Here are some of the people who increased
my understanding of it.
Thank you very much.
- Great. Thank you.
So now we have time for questions.
I see maybe there's some in the chat.
One from Charlie is, "What is causing
the nutrient enrichment in seepage forests?
Bedrock, till chemistry, hydrology,
topographic, or climactic?"
- Hmm. A very good question.
I think when it comes to the mystery of water
under the ground,
I'm not really sure exactly what's going on.
I assume.
I'll say what I assume though.
I assume that it is coming from the groundwater
that's made contact with bedrock and/or till,
and come out with a higher nutrient content
and at a higher pH.
I don't know, but that's what I assume.
So I assume it's one of the first two choices,
bedrock and till chemistry, for the most part.
I should say that, yeah, till chemistry
might play a big role.
There is some, Hannah Phillips speculated in her work that-
- Uh oh, you were muted, Dan, somehow.
- Oh, can anybody hear me?
Yeah.
So sorry.
So I'll start over. 'Cause none of that was heard, right?
- We heard in the beginning, but.
- Oh, okay.
Well anyway, I would say it's one of the first two choices,
bedrock or till chemistry,
but I am a little uncertain
as to how things go under the ground.
But there, there are possibly more acidic versions,
I just haven't seen them myself.
- We have a hand raised from Sean.
And then we have a few more questions in the chat.
- Great.
- Yeah, Dan. I really, enjoyed your talk.
It's just fascinating to hear about these.
And I've seen communities like this in Northern Maine,
but they're often really small,
like typically less than one acre.
But then, your map showed some,
what seemed like really large polygons.
Are they really that large where you find them in Vermont?
- Yeah.
Yes. And those were, I mean, I think those were on,
I think that was about 20-plus acres in total.
And there were other places
that are larger on, near the same location.
Those might be some of the biggest ones, you know,
the ones that are most obvious.
That those are actually ones
that some of those are ones that Hannah found,
not the ones actually I showed, but Hannah Phillips.
And so I might've been directed towards a very good spot.
Liz Thompson said they go on forever in that location.
So they might not, I don't know
if we'll find anymore that big.
Yeah.
- Okay. Thank you.
- Yeah. Thanks.
- There are several very good questions in the chat,
but we are over time.
So I don't know, Dan, if you are willing to hang out here.
- I'm willing to hang out
if anybody else is. - I'm gonna hop
to the next one,
but if anybody has a question, sounds like Dan will stay.
And then we'll be moving on
to our next contributed talk at 10:25.
Thanks again, Dan.
- Thank you.
Oh, okay.
So I'm gonna read the chat to find some questions,
unless anybody wants to ask them to me directly.
So this is from River Matthew.
"This is really interesting stuff. Thanks,
presenting this information.
I'm wondering about the importance of black ash
to seepage forest in the northeast.
What do you think of implications of emerald ash borer
and black ash mortality may be to seepage forest?
What species make up the regeneration within these forests?
And are there signs as to what species may replace black ash
within these forests?
So these are great questions.
And it did come up in, Hannah's sort of speculated
about a little bit, Hannah Phillips.
I think.
And also that's what the work that Tony D'Amato
coauthored about the black ash swamps in Michigan,
was actually about what would happen
if these wetlands lost their black ash.
And I think the idea is that there are,
I think that they might water up, so to speak,
that the water table might raise
if we lose the black ash
that's in the wettest portions of these of these forests.
And that might kill other species
or make other woody species not be able to survive there.
And they could convert
in a similar way to if the canopy was removed.
So we don't really know, but that's sort of a guess.
And we've seem to have found this kind of activity,
not when cuttings happen in these forests,
but we still have a lot more to learn.
So these are really good questions.
And I think we just have to pay attention.
I'm gonna keep going, unless anybody wants to jump in.
"Is there a place where people can report
and provide coordinates for new discoveries of this forest?"
Yes, you can contact me.
And I should put my email in the chat.
And in general, you can contact us
at the Wildlife Diversity Program
at the Vermont Department of Fish and Wildlife.
And if there's potentially state significant occurrences
of these, and I'll sort of leave it there, but please do.
And I would encourage it.
You know, I sort of hope we find,
that's what this presentation is sort of about for me
is to spread the word and get more information.
Nancy Patch.
"I have real concerns about forest management
in Eastern communities.
They start with low market feasibility
and are extremely difficult to regenerate,
needing big wood on the floor and tip ups
for seedling establishment.
Thoughts on this?
The Northern Green Mountains in Northwestern Vermont
may have large seepage forests."
Yes. I've seen some of those. I want to see more.
So, yeah, I've seen a lot of,
I think a lot of seedlings growing on tip ups
and regenerating on tip ups, on the logs themselves,
decomposing logs and the root balls.
Yeah, I think, I agree with all of that.
I don't know if I can say much more than I agree
that management seems to disrupt these,
or would seem to disrupt these pretty significantly.
Yeah, and also, it's also a part of the recommendation
to try not to disturb the topography
or when you're working in these forests,
to preserve that sort of hummock hollow,
which would be important for that.
We are at time.
And I guess, let's see.
I'm gonna take.
"Echoing Nancy" from Tony McCullough.
Hi, Tony.
"As someone who reviews chip harvest jobs in the state,
I wonder if this,
what needs to be done to protect seepage forests,
especially since they aren't mapped?
I think they need to be delineated in the summer.
You need to go out and find out there where they are
because you can't really see
where they are in winter often.
And I think they should be flagged off.
I've seen that when I've been in the field.
And I think that's good for starters.
So I guess, oh, there's my presentation,
I mean, my email.
Great. Thank you.
I guess I'm gonna leave it while Charlie,
"Pedohydrology at the Hubbard Brook,
especially at Scott Bailey, had been studying change,
the charging and flow paths are very important."
Interesting, cool.
More things to think about.
All right. I guess that's it.
I better close out.
Everybody's got to get to another show.
All right. Thank you very much.