Good morning, everybody.
I'm Ryan Rebozo, Director of Conservation Science
with the Vermont Center for Ecostudies.
I'm gonna talk today about a pilot monitoring project
we got off the ground with our partners
at Raritan Valley Community College and also in partnership
with the Green Mountain National Forest and TNC.
(indistinct) In just a minute,
a real quick minute here on the natural community type
that we're interested in.
Dry oak forests can be found
in all the states in FPMC region.
They're considered an uncommon natural community.
They're S3 in Vermont.
As the name suggests, the components
of sand and the soil maintain relatively dry conditions
and it's dominated by red oak.
To me, I'm interested in this natural community
because as the use of fire
is gaining interest in the Northeast
as a management tool, and for good reasons,
this is the type of habitat that kind of stands out
as the potential, you know, use of fire
to maintain this system.
You look at the understories, they're dominated
by Ericaceae shrubs and subshrubs,
again, fire-adapted,
but unlike some other systems that I've worked in,
and luckily we're gonna hear more about in the next talk,
pitch vines that are very fire-adapted.
There's a lot of questions about the use
of fire in oak systems.
You look at the literature
and you get a little bit of a mixed bag, right?
You have opportunities where you see studies
that have found really good examples
of fire creating the conditions needed
to maintain oak-dominated systems, maintain oak germination.
But then you also have examples where the use
of fire may have had detrimental effects to these species
that we wanna prioritize.
And the question is, how do we best monitor these systems
to tell that story and identify where it's appropriate
and if we're on the right track of management?
All right, well, so we tried
to look at a couple different things here, right?
One is to develop this kind of robust list of variables
that we might monitor
that are gonna complement the common stand exam
that the National Forest was using at the site, right?
The kinds of things that we think can give us an idea
of the conditions on site, initial response to fire,
and how this system might be changing in its trajectory
in time to see if we're reaching our management goals.
Now, you know, the second piece
of this is refining that a little bit.
It's easy to throw out, you know, a bunch of variables
to monitor, but we know as you add more conditions
to look at in a monitoring protocol, takes longer to do
and becomes more expensive.
So my interest is taking a look at that broader scheme
of variables and narrowing that down
to which ones are really telling the story best
and using that as as our monitoring protocol
in moving forward.
The third piece, which I really won't have time
to talk about today, is taking a look at the use
of technology to help us expand
and improve upon our monitoring methods.
So we did this in a few different ways.
I'll touch on our use of drones a little later,
but we used ARUs for some, you know,
sound recordings at the community level.
We used, this is a bad picture,
but that down on the bottom is a BLK360 Leica scanner,
so it allows us to take really high-definition scans
of the forest understory that can really, again,
be a useful tool moving forward.
Again, the question is, are these pieces
of tech worth that upfront cost?
And what are we gonna gain in our kind
of long-term monitoring sites?
How is it gonna improve on our field-based methods?
So I'm just gonna talk about a little piece
of what we looked at that I think has applications
beyond the use of fire, beyond oak habitats.
And I'll just hit on our sites real quick.
This was an opportunistic study, right?
We had a chance to go in and visit a site
after it had been prescribed burn.
This was down in (indistinct) Vermont,
in the Green Mountain National Forest,
a site called the Dome.
It's a pretty great example
of this dry oak natural community.
Conveniently, there's a trail that bisects it
so that one half was subjected to a prescribed burn,
the other half was left as an adjacent control.
We also added a satellite control site up in Fairhaven.
This is a property of the Great Ledge Natural Area,
another prime example of dry oak habitat
that's owned and managed by the Nature Conservancy.
So I keep saying management, right?
Prescribed fire is a management tool.
So if you have it, if you're using a management tool,
you have some management goals, right?
So if we take a look at the five-year goals for the use
of fire in these sites, it's going to address concerns
with changes in species composition, right?
The national forest is working to be good stewards
of this natural community on their land
and they're concerned
that we have conditions of mesophication
where you have species specifically called out beech
and maple that are creating conditions that are beneficial
to the germination of conspecifics
more so than than some priority species,
in this case red oak.
So some of the five-year goals,
reduce stem density of these species.
In addition to beech and maple,
birches and cherries were called out in the plan,
and also use fire to increase the competitiveness of,
in this case, red oak to maintain an oak-dominant system.
So that is maintaining oak as the dominant canopy tree
and also promoting oak seedling germination as well.
That's the big, you know, five-year plan.
But every specific fire
has its own management goals as well.
And we followed a bay fire where the goals
were to introduce on the order of about 75% mortality
to the sapling class, consume the duff layer about one
to three inches, and reduce fuel load overall.
Again, we kind of had this nice opportunity.
It was again, opportunistic, taking advantage of management
that was already ongoing on site to kind of pilot some
of these strategies and some
of these techniques in an area
that was within the first year of regeneration after fire,
and then control sites as well.
So how do we do this?
We wanted to start off with methodology that was accepted
by the Forest Service and was easily replicated.
So we worked with FIA Phase 3.
A lot of you probably are familiar with this FIA.
Forest Inventory Analysis has different phases
and each phase gets a little more comprehensive.
So Phase 3 I think does a good job
of telling the story from our canopy trees, saplings,
shrub layer, herbaceous plants,
and things like woody debris, ground cover.
It kind of paints a good picture
and is, like I said, I think easy to replicate.
I kind of have a little drawing there on the top right.
Each of our sampling locations is broken up into subplots,
micro plots, quadrants, transects,
so that we're sampling at the appropriate scale
for the variables that we're interested in.
We won't really be able to hit on too many of these,
but I'm gonna, again, just focus on one piece
that I think is interesting that will tell us a story.
Hopefully we can continue this
and really get this idea of changes
and succession over time.
Don't worry about the colors here.
They represent different species.
I'll touch on that a little bit in the next slide.
But what we're looking at is stem density
by size classes, right?
If we start on the left, our highest densities
are in the seedling size classes, right?
Exactly what we'd expect.
These are gonna be first year plants that even in the case
of the burn sites are germinating after the fire
and they haven't experienced the mortality that we expect
to see in this light class, right,
where that density is gonna drop down.
If we go over to the far right,
these are our two largest size classes.
These are your canopy trees, four to 10-inch dbh,
and 10 plus plus inch dbh.
You expect lower densities here, right?
Larger trees, more space.
They've been under competition for a longer time.
These are the ones that are up in the canopy.
I think I'm most interested in what's going on
in these sapling categories, right?
The ones that I'm particularly interested.
The three- to five-foot saplings, five- to 10-foot saplings,
and 10 plus foot saplings, right?
I think what's interesting about these
is they're obviously the connection
between our seedling class
that we wanna see recruited into the canopy, right?
We wanna see kind of as much of the stem density
as we can to survive
and ultimately make their way into the canopy.
It's also interesting to me
because this is the size classes that from some
of our previous work, and again with my partners
at Raritan Valley College, we found that,
you know, impacts to the sapling size class
can take on the order of 10 to 15 years to recover.
So this is kind of, you know, telling the story
of what our trajectory is gonna look like.
So we see lower densities in that size class.
And now if we look at species composition,
I think this tells another piece of the story, right?
Some of that reduced density is by design, right?
One of the management goals was to reduce stem density
in the sapling layer by about 75%.
And that was a success, right?
It was on the order of about 90% for the three-
to five-foot size class, 80% for the five- to 10-foot class,
about 55% for 10 plus foot saplings.
If we pay attention to just one color here for now,
and not to, you know, get too crazy here,
the dark blue is what we're looking for
if we're interested in red oaks, right?
So if we start on the right, we can see that the canopy,
the largest diameter trees are still very much dominated
by red oaks.
If we work our way back over to the seedling class,
we see that oaks are a component,
but they're sharing space with a greater diversity
of species at this size class.
Slightly less seedling germination post-fire.
And that, you know, probably makes good sense.
You're gonna have some acorns consumed
after the fire, those that weren't insulated by the duff.
But even in our control sites, we had between 10%
and 30% of the seedling community
was still made up of red oak.
What we're missing now is we're starting to see some
of these oaks drop off when we're getting
into that sapling class.
And again, I think I tend
to come at this from a population level,
and if we're thinking about, you know, population viability
of in this case oaks,
we wanna see which life stage transitions
will make the biggest impact
to that viability in time, right?
We don't have those data yet to make those assessments
since it's kind of just our first stab at it.
But it seems to me pretty likely
that that transition from the seedling stage
to have greater survivorship into the sapling
is gonna really tell the story of the success of this site.
Again, it's doesn't seem to be the case of fire
for this low red oak composition in the sapling community
because we're finding it in our two control sites as well.
Kind of to round this out and try to identify what some
of these selection pressures might be
from going into the size class,
we took a look at a couple other things,
two of which included insect herbivory and deer browse.
And probably not surprising to many,
we found pretty high levels
of deer browse on site on the order
of about 80% in some of our sampling (indistinct).
So what we did is we decided to take a good look
at deer density on site, local densities,
and we used a infrared camera on a drone for this.
We did this in April.
There's a couple reasons for that, right, prior to leaf out,
so you have really good contrast of the deer
with the surrounding area around them.
So we have good confidence in our local estimates.
It also, I believe,
will give us the most conservative estimate
of deer density on site
because it's after the hunting season,
after winter mortality, but before fawns are born, right?
So we did this, we took into account average home range
for deer in New England.
We ran parallel transect lines
with the drone about 500 feet apart.
And you know, to me it's a way to have
a really good confidence in your deer density
and cover a lot of ground in a short amount of time.
So what do we find?
We found 10 and 12 deer per square mile,
10 Green Mountain, 12 up at the Great Ledge Natural Area.
And I think this might, you know, begin to round out
that story about deer browse we're seeing on site.
This is about the density that the literature suggests
you start to see impacts to preferred browse species,
and we certainly know red oak
is a preferred browse species of deer.
I think a couple other things to point out here,
as I mentioned taking, doing these surveys in April
to have our most conservative estimate,
I think the last time I checked, some the estimates
of the number of fawns per per doe in Vermont are about 1.6.
So, you know, we're looking at about 10
to 12 year per square mile.
That number can go up as much as 60%
during the brown season.
I kind of highlight this specifically.
This is just a piece of our larger monitoring
because again, I mentioned I think this has applications
beyond just fire and oaks,
but can certainly tell a story here of one
of these other conditions
that we wanna take into account when we start
judging our kind of management, our goal,
our progress towards management goals, right?
Are we getting there?
What might be selection pressures?
So fire did a few things successful
right after introduction, right?
It was able to consume the leaf litter,
kind of working on that seed bed.
We saw that in that we continued
to get oak seedling germination
after the fire, that same year after the fire.
The targets for sapling mortality were reached.
Invasives did not make their way into the sites.
But that's another piece that I won't have time to get into.
Time is gonna tell how our shrub
and seedling response is gonna work, right?
But as of now there is still good seedling germination.
There's on the existing seed bed.
One piece of the study was also taking a look at rare plants
on site with the hope
that if we continue this we can get an idea
of how those populations track with fire,
both initial response and long-term response.
In addition to rare plant species themselves,
we had a particular interest in plant species in genera
that support rare or specialist pollinators.
I think that's an interesting component
if we're looking at more community level responses
to fire to work into this monitoring plan.
But some of the concerns is duff layer consumption
wasn't reached, and that's not surprising, right?
Duff layer holds a lot of moisture, gets compacted
with snow load.
It's very hard to consume that with a first
or even sometimes second introduction to fire.
So that's something that comes presumably in time.
We're introducing more intense burns.
And deer density does appear to be driving
the life stage transition from some
of these seedlings we have on site to saplings,
probably more, or at least in addition
to interspecific competition
and what we think the fire might be doing onsite.
So, you know, some concern on that level.
I mentioned a little bit about these rare species.
I think I'm just probably at time,
so I'll take any questions you have.
Yep.
[Participant] Yeah, there's been a lot
of controversy about oak dependence
on fire, oak regeneration.
Do you have any evidence of fires in these two places
before you started the experiment?
So, charcoal, historical records, that kind of thing?
Yeah, not from my own data collection,
but the Forest Service has done that work in the past
and we have found fires in the past century
at these sites.
I think you're right, though.
There is a lot of question
and I think my interest was in dry oak habitat specifically
because of that understory community
that really suggests fire-adapted.
I think there's a lot of questions as I'll turn, you know,
what was past fire return interval, past intensities, right?
I think there's a lot of questions there,
more so than other fire-adapted systems,
but I think there are some signs
that suggest fire has played a role here in the past.
Good question. Yep.
[Participant] On that note, do we have any information
about seasonality of fire historically,
because at least in my region,
we have hugely different responses
from at least the (indistinct) community
based on what season you burn in,
whether it's spring or winter.
Yeah, I think that's a big piece
of fire management in general, right?
I think if you're managing
for fire-adapted species response, it's likely
that growing season burns are gonna create the conditions
that we often talk about fire doing, right?
I think sometimes we talk about the use
of fire in generalities that you're gonna introduce fire
and you're gonna create all this early successional habitat
or you're gonna consume duff layer.
But that's often very difficult when fires are happening
in late winter, early spring.
I think, you know, under natural conditions sometimes spring
and fall become the fire seasons
because the leaf litter can dry a lot faster
without the cover.
But I think you're right.
I think some of the limitations
we might've seen, specifically with the duff layer,
were due to the season in which the fire happened.
Oh, yep.
An online question.
Sylvia?
Hi, Ryan.
This is Lindsay Ray Sylvia.
Can you hear me all right?
Yep. Yeah.
Hey, field technician
from the Green Mountain National Forest.
To answer that first question
or just to help provide a little more intel,
we did have a sample of a red pine tree
from the Dome analyzed by Dr. Mike Stambaugh,
a dendrochronologist out of University of Missouri.
And his analysis provided that the fire historical,
like return interval was about that six to nine years apart.
And that was up until guess when.
Early 1900s, right?
When fire suppression
became more common on the landscape.
So I just wanted to provide that as some intel
to that original question about fire return
and history on site.
I think that's kind of an interesting piece
because that's a very high fire return interval,
especially for an oak forest,
so that six to nine years is, thank you.
[Participant] I'm curious what the canopy cover was
and if you felt that there was too much
overstory tree canopy in there
and how that might've influenced,
you know, the effects of the fire.
Good question.
In most cases where we kind of had that intact canopy
was about 85% covered, so 15% openness.
I think, you know, locally there was probably more light
reaching the forest floor than that
because there was plenty of signs of diseased beech
and then we know that there has been
spongy moth impacts there in the recent past.
Another online question.
[Participant] Hi. Thank you.
I was just curious if you're aware
of any fire-adapted communities
that have kind of already succumbed to mesophication
and whether you're aware of kind of what the threshold is
or kind of like the point of no return for pulling those out
of that process.
That's a good question too.
You know, I've read about examples
of some of these areas that have gone
through species composition change,
whether they're oak forests or other fire-adapted systems.
The point of no return is an interesting one
and I don't think I have a good sense
of what that might be, and that's probably specific
to the natural community.
It's probably specific to fire history
and how, you know,
fire could even have a chance to return it.
But I don't have a good answer for that, unfortunately.
[Participant] How thick is duff layer,
and what kind of soil is it?
So we did take a look at...
It's a sandy loam,
and I'm blanking on the name of the exact soil type.
If it comes to me, I'll let you know.
Duff layer was about five to six inches.
And again, that was pretty consistent
among both our two control sites and the burn site.
Leaf litter at the burn site was much closer
to what we had in our satellite control site,
which had good seedling germination.
So even with that thick duff layer, I think we have
a seed bed that has the potential
to kind of still maintain oak germination
because we're seeing that on that satellite control side.
[Announcer] I think that's all we had time for.
We're gonna get them together for the next one.
-Thank you. -All right.