- For this last talk of the technology and innovation track,
we have Al Freeman here, a PhD candidate
with the Rubenstein School of Environment
and Natural Resources within the University of Vermont.
I will be sharing their presentation titled
"Assessing the Efficacy of Assisted Migration,
Physiological Response of Seedlings to Moderate Severity
Drought and Adaptive Civil Culture Treatments."
- [Al] Today I'm gonna be talking about
the physiological response of future adapted seedlings
to a moderate severity drought
at the adaptive civil culture for climate change project.
It's important to note that climate regimes
are actually changing at a much faster rate
than natural migration has keep pace with.
And so recent species distribution models
are actually showing that the Northeast
is gonna be prime for migration
with increases in habitat for future adapted species
that are expected to either enrich
the population of the site.
So again, these species that are found there,
but aren't in high abundance
or as species that are not currently present on the site,
but may increase their range.
And so this lack of natural migration
and potential for this new suitable habitat
has led to the idea of using a system migration
to aid kind of in climate adaptation of our forests.
Because effectively transitioning forests through management
will take decades,
it's really important that we start investigating right now,
how we can best shift our ecosystems
towards these more novel states
and build mechanisms to resist
these changing climate regimes.
And so three different strategies have been proposed
as a means for managing with climate resiliency in mind.
So the first one is resistance.
The goal of this is really to improve defenses
of forest management against change
and disturbance by maintaining
kind of relatively unchanged conditions.
Second treatment is resilience.
And so resilience adds a bit more complexity to the system
and accommodates some degree of change
with the ultimate goal still being to return to
a prior reference condition following disturbance.
And this can be accomplished by performing
some civil cultural prescriptions,
like a matrix of thinning with varying gap sizes,
to add a little bit more structural complexity
into the system.
Last, we have the transition treatment,
which is intentionally trying to facilitate change
in the system and surprise,
transition the site to be adaptively responsive.
And so this can kind of be accomplished
through creating a matrix of thinning with gaps
and planting those species
that we kind of talked about before that are future adapted,
to add a little bit more variation and complexity.
These three different strategies have led to the development
of what is referred to as the
Adaptive Civil Culture for Climate Change Project
or the ASCC Project,
which is the largest replicated forest management experiment
in the Northeast U.S.
And it was co-produced by managers,
scientists, biologists, and stakeholders.
So it's this huge effort that has led to the development
of these effective strategies for forest management
with climate mitigation in mind.
The main goal of the project is to implement actions
that are robust across a range
of potential future conditions.
The ASCC Project is located at the Second College Grant,
and you can see in this figure here below,
this is kind of what the treatments look like.
So we have the control treatments here.
We have our resistance treatments, our resilience,
so adding a little bit more complexity in there,
and then we have our transition treatments
where we have quarter acre and one acre gaps.
And within these gaps,
we have actually planted seedlings that are expected to have
either a population expansion or enrichment.
So again, species that are found on the site,
but we're increasing the abundance of those individuals
because they're expected to perform better
under future climate conditions.
We also have species that are
expected to have a range expansion.
So ones that are not currently found on the site,
but under future climate conditions,
they are expected to have this range shift more northward.
And so all of these species,
there were nine selected in total,
they were planted in 2016.
For my research, I selected an example of
a population enrichment planting.
So I selected red oak and then two range expansion species,
black birch and American chestnut
with the goal being to kind of
evaluate their response over the growing season
in order to better gauge their adaptive capacity
and performance out at this site
in these varying gap sizes.
And so understanding how these species are gonna respond
to current conditions can give better insight
into how they may behave in the future.
And specifically I'm interested in determining
the drought sensitivity of these species.
And it just so happens that we experienced
a moderate to severe trout this summer.
As some background,
it's important to note that there are two varying strategies
for dealing with drought stress
that have to do with the stomata of the plant.
So stomata are essentially the nose and the mouth
of the plant.
It's where carbon assimilation is occurring,
water vapor is lost and oxygen is released.
And so there's two different strategies
referred to as isohydric and anisohydric.
And so for isohydric species,
when there's increased atmospheric demand for water
and declining soil water availability,
these species have this tight stomatal regulation.
And so they're able to close their stomata
to kind of prevent further water loss,
but they also are in turn
lowering the amount of photosynthesis they're occurring
because they've closed their stomata.
Drought tolerant or anisohydric species
behave in the opposite way.
They keep their stomata open for longer periods
during drought conditions
and so they're photosynthesizing at higher rates
while markedly reducing their water potential.
And so if we were to anthropomorphize this kind of behavior,
we would say the isohydric species kind of
behave in a more cautious manner
while anisohydric species kind of display
this more daring behavior.
And so species and gene,
species that are considered isohydric would be,
you know, black birch, whereas anisohydric species
would be northern red oak.
So building off of these strategies
that these plants kind of exhibit,
the ultimate goal of my research is really to determine
the physiological response to a moderate
and severe drought of the selected tree species
to kinda get a better idea
of how they're performing on the site.
And so one method used was measuring the predawn
and midday water potential of these plants.
And so basically what you do for this,
so at pre-dawn water potential,
you go out pre-dawn and you get an assessment of the water
status of the plant, because you know,
they're not going through any stressful conditions.
They're kinda at their fullest and happiest.
And so then from there you go back in the midday,
when things are a little bit more stressful,
you kind of at the heat of the day
and you measure that water potential again,
and you can get an understanding of how far
they've deviated from that baseline.
And that can be indicative of how much tension
and water stress is that plant under.
And this has done so using a Scholander pressure bomb here.
It just puts the plant under positive pressure
and kinda draws that water back up through the plant.
We also measured the photosynthetic capacity
of the seedlings and this was done so using what is called
an LI6400 made by LI-COR.
It's this heavy piece of equipment that you get to
lug up and down a mountain and clamp to the leaf
of the plant of your choosing.
And essentially you get a ton of different measurements
that can kind of be indicative of
the rate of photosynthesis that is occurring in the plant.
And so with these measurements,
we are expecting that this difference between
the pre-dawn water potential
and the midday water potential
would be pretty high for the anisohydric species.
So implying that that difference,
that deviation from the baseline would be much higher
because they're risking being,
leaving their stomata open in order to gain more carbon.
On the other side of this,
we would expect that the isohydric species
would have less of a difference between pre-dawn
and midday water potential, because again,
they have that tighter stomatal regulation.
And so they're keeping their stomata closed
during periods of drought.
Regarding photosynthesis, we would expect that
the anisohydric species,
so again those drought tolerant species like red oak
are going to have high rates of photosynthesis
during periods of drought stress.
And on the other end of that,
we would expect the isohydric species like black birch
and potentially American chestnut
to have lower photosynthetic capacity,
because again, they're shutting their stomata
during these periods of water stress.
So here is what we found in terms of water potential.
And just for some context to kinda explain this figure,
we did four different sampling periods
over the growing season.
So we had June, mid or early June, mid June,
July and August.
And during this period,
we had an abnormally dry period, a moderate drought,
a severe drought and another moderate drought.
And so what we really saw is that the,
between species water potential,
that difference between that pre-dawn water potential
and midday water potential
did not really vary between species.
They were all pretty similar in their response.
However, we did see that the difference
between pre-dawn and midday water potentials
decreased in all species in response to
these drying soil conditions,
especially during these periods of severe
and moderate drought in July and August.
Looking at the photosynthetic capacity,
you can see here for black birch,
we had low photosynthetic rates during that severe
and moderate drought in July and August.
So they kind of shut down their stomata
during these periods of extreme water stress.
And so this is again,
exhibiting that isohydric behavior
that we expected to see.
For American chestnut,
you can kinda see that this species maintained
a pretty consistent photosynthetic rate
throughout the growing season.
August in June photosynthetic rates did vary significantly,
but other than that, they were pretty steady throughout.
And so this is exhibiting a moderate anisohydric behavior.
All right, and here's the star of the show red oak.
So red oak in June
had pretty consistent photosynthetic rates,
but then during those periods of severe
and moderate drought in July and August,
you can see that they had these high increased
photosynthetic rates in each of these months.
And so they are strongly exhibiting
this anisohydric behavior.
When comparing across species for the month of June,
where we had the abnormal dry period
and a slight moderate drought,
red oak had greater photosynthetic rates
than American chestnut,
not so much against black birch.
In July red oak again had greater photosynthetic rates
than both American chestnut and black birch.
And then in August again,
red oak had the highest photosynthetic rates
compared to the other two species.
And so it's just really performing well
during these periods of high stress.
So again, we were expecting to see that
that difference between the pre-dawn water potential
and midday, that would be highest
for the anisohydric species
and lowest for the isohydric species.
And that photosynthetic rates would be high
for the anisohydric species, red oak
and lowest for the isohydric species, black birch.
And so what did we actually see?
Well, we saw that actually for the delta water potential,
so again, that change between that baseline
and the most stressful time of day
was actually high for both isohydric
and anisohydric species.
So black birch and red oak and American chestnut
all had very similar differences in their water potential.
We also saw that photosynthetic capacity
was what we expected.
So very high for those anisohydric species
that keep their stomata open
during periods of stress
and lower for the isohydric species,
that again, behave in a little bit more
of a cautious manner.
So really the big takeaways from this is that
as we anticipate these changing climate regimes,
these future adapt to species do seem to be responding
in a way that is pretty promising.
From previous studies, we've noticed that there is
higher survivorship for the anisohydric red oak,
however these do exhibit lower growth,
so they're a little bit slower in their establishment.
But on the other end of this red oak and American chestnut,
so this, you know, typical anisohydric species
and a moderate anisohydric species
are expected to tolerate these moderate to severe droughts,
which are expected to increase in frequency.
And so although there is some risk
in maintaining that open stomata during periods of drought,
there's also a huge gain regarding
this establishment for these species
and that could give them a competitive edge in the future.
And although black birch is expected to have suitable
habitat further north based on these changing temperatures,
these species still do prefer moist climates
and so they may struggle with persistent severe drought.
Taking this a step further,
I'm really interested in understanding these mortality
thresholds for these future adapted species
that are expected to have either a population expansion
or a range expansion.
And so I'm gonna be exposing the species
to a precipitation exclusion
with the ultimate goal being, you know,
how much water stress can these species experience
before we start to see declines in survival.
Beyond future adapted species,
I'm also very interested in determining how the resistance
and resilience treatments are going to impact
overstory species in terms of their water relations.
And this will be done so using carbon stable isotopes
to better gauge how water stress is occurring
based on civil cultural treatments.
And with that,
I just want to acknowledge all of the amazing people
that have helped me with my past project,
as well as these future projects that I touched on.
I'm just very fortunate to have such an amazing
and supportive lab and group of people to work with.
And so I will take any and all questions.
- Thank you so much for that informative talk.
- [Jerry] I have a question, Jerry in New York.
Do you think that these data are really good example
of why it would be beneficial to re-introduce transgenic
chestnut to the landscape for climate change mitigation?
- Well, so we unfortunately
didn't have the transgenic chestnut planted on the site.
Most of these were the hybrids.
but there are studies that are going on
with the transgenic chestnut
that may be a little bit more useful
to provide that information.
but I definitely think that these kinds of methods
would be useful and beneficial to understand
like how it may perform at a site.
So I think carrying forward, it would be worth,
you know, doing all of these measurements
in areas where we do have planted transgenic chestnut.
Hopefully that answered your question.
But I would love to.
If I had the opportunity,
I would 100% do a study with the transgenic chestnut.
I just think it's a really, really cool project.
It looks like there is a question in the chat.
It says, I'm wondering which other future adapted species
for this region you're interested in exploring
mortality thresholds for.
Yeah, so for this upcoming summer,
I'm gonna be measuring black cherry, bitternut hickory,
basswood, red oak,
and why am I blanking on the last one?
Black birch, yeah.
So those are the ones that we're focusing in on.
I'm especially interested in bitternut hickory,
just because it is a pretty far rain shift
and so I'm interested to see kinda how it's gonna be doing
in our rich Northern hardwood,
that's a little bit further north than it's expected to be.
But there's also at the project
that I didn't get to measure, there's white pine.
We have Eastern hemlock,
big tooth aspen.
So there's a lot of different species that are being planted
that we're assessing.
And so those that are at the Second College Grant,
we do have long-term, for the last five years measurements,
on growth and survivorship, that's gonna be carried forward.
So hopefully that answered your question Madeline.
- Hi Al, nice presentation.
I'm curious, did you see any patterns
in the pre-dawn water potentials
over the course of the season for any of your species?
- So the pre-dawns were all pretty consistent.
They definitely started, you know,
they were starting at a more negative water potential
in those severe to moderate droughts.
But for the most part,
like across species, they were all pretty consistent.
But I'm hoping, you know, doing this precipitation exclusion
and like really stressing them out,
I'll start to see some more clear trends.
- Cool, thank you. - Yeah, of course.
So is there a wide genetic range
within species for these traits?
So we were pretty limited
since the Northeast does not have a lot of plantings
or just like, we just don't really plant
whenever we do civil culture or forest management,
it's just not a big part of our management here,
since we don't have to,
we have so much advanced regeneration.
So we were pretty limited
in where we could get our seed source.
And so there isn't a ton of genetic...
We didn't do a lot of provenance studies with this.
So hopefully in the future we can, you know,
have some more provenance studies,
but that wasn't a big part of these plantings.
Hey Tom, how's it going?
- Hey Al good to see you. - Good to see you too.
- Great presentation and really, really good work.
So I've got a question that may be unfair to you,
but I'm wondering if there's a relation.
Well, let me back up,
both of your anisohydric species are rain porous.
Is there a relationship relationship
between the vessel structure
and the behavior of the stomata?
This this is new to me.
- Yeah, so typically diffuse porous species
kind of lean more towards the isohydric range.
I'm not 100,
I can't give you an answer exactly why that is,
but that does come into play.
So those functional traits do have a role in terms of,
you know, the drought response.
And there's actually a paper that was just released
that has a bunch of different traits
that they're finding that kind of those functional traits
that divide them into isohydric and anisohydric.
And so that is, that is one of those.
- Yeah, thanks a lot.
This is new to me.
This is just fascinating.
So thank you.
- Yeah, of course.
- Al, that was a great presentation
and really interesting to me.
So I'm curious if you think as age increases
with those species,
do those characteristics change in the plant?
- So I think they still behave pretty similarly,
but you definitely I think see more extremes
probably whenever they're younger,
just because things are a little bit more competitive.
But one thing that I am looking to do,
so in all three of the treatments,
the resistance, resilience, and transition,
I'm gonna be taking tree cores of overstory trees.
And so that can give you,
when you do carbon stable isotopes on those,
you can get the relation of C-13 to C-12,
which is kind of what they're fixing.
And so to make a complicated topic less complicated,
so basically if they're closing their stomata more
because they're really stressed,
they're gonna deplete that like lighter C-12,
and use more C-13.
So if you have a higher ratio of C-13 to C-12,
it tells you that the plant was more stressed
and closed their stomata more.
Hopefully this is making sense. (laughs)
- Yeah, it is making sense,
but there's a lot of things going on there
and it's really interesting. - Yes, no, absolutely.
- You know black birch for instance,
seems to be really doing well you know,
in Southern New England like Connecticut.
And so you think of it as being a species
that that may be climate resilient,
but yet what you're finding is that certainly
as you're moving north, it may not be as resilient.
- Well, so that's also one of the benefits
of the drought study is to kind of see what its limits are.
Because sometimes being isohydric
can actually be beneficial
where you're being a little bit more cautious,
especially if we're not gonna have huge, severe droughts.
So playing it a little bit more cautiously can be hugely
beneficial in like, you know, shorter term droughts.
Whereas like, if you are leaving your stomata open,
if you're depleting your water and water doesn't come for,
you know, another month,
you actually may have higher rates of decline.
So it's very complicated and kinda hard to tease out,
but I'm hoping through both of those kinds of lenses,
I can have a clearer image of how these seedlings
are gonna do outside of their typical range.
- Well I like the lens.
So it's very cool, good luck.
- Thank you so much.
- [Jerry] Yeah, I have another question.
I'm fascinated by the carbon-13 and carbon-14 variants
that you've mentioned just now.
Could you conceivably go out and collect cores
and then take those cores to a lab somewhere
and get that difference analyzed by year?
Yeah, I see you nodding your head.
Yeah, yeah, no, exactly.
So it's gonna be it's C-13 versus C-12
for what I'm looking at, but you, yeah,
so that's what you basically go out and do
is you go out and core these trees.
And I'm gonna be looking at the different treatments,
so like the matrix thinning versus the gaps
versus just control,
and then you send that to a lab to get analyzed.
So that's definitely- - How difficult,
How difficult is that analysis?
- Well, I'm paying somebody,
so I basically just core the tree
and then you grind down the samples
into these fine little balls that you ship off.
So I have never actually
performed that analysis. - And so are you doing
that by tree ring,
you know, by age? - Yeah.
- Yeah.
- [Jerry] Okay, how much does that cost?
- Ooh, that's a good one.
- It's a... - It's fascinating.
I'd like to maybe try some of that.
- I don't know, off the top of my head,
how much it costs and it depends on the lab you send it to.
So there is a really great person at K State
who does a lot of carbon stable isotope work,
but I think there's other places in New England.
But if you email me, I'd be happy to,
you know, send you some contacts,
if this is something you're interested in doing.
- [Jerry] Well, I'd have to figure out
how to put a study together on that.
But certainly the impact of climate change
and drought here in New York is where I am, is huge.
- Yeah, no definitely. - Yeah.