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- I'm happy to introduce Jordon Tourville,

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a PhD candidate at SUNY-ESF,

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College of Environmental
Science and Forestry,

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conducting research with the
Appalachian Mountain Club.

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Jordon will be presenting
Forests on the Move:

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Tracking Climate Change in
Montane Forest of the Northeast.

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- Okay, thanks everyone
for coming to this talk.

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I'd like to share a bit
about a collaborative project

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between the Dovciak Lab at
SUNY-ESF, the Sussman Foundation

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and the Appalachian Mountain
Club represented here

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by David Publicover and Sarah Nelson.

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Looking at the spatial
dynamics, demographics,

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and drivers behind treeline
and treeline locations

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on several slopes across the
Northeast in montane systems.

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If we run out of time
for questions at the end,

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please feel free to email
me at the address here.

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So here we go.

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So to start with very basic definitions,

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what are treelines?

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Treelines are the locations
usually on montane slopes,

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where trees can no longer
maintain a tall, upright form

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generally due to harsh
climatic conditions.

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And because the location of treelines are

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so tightly linked either directly

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or indirectly with climate factors.

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These are thought to serve
as sort of a barometer

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for climate change.

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Several groups including
the Melanie Harsch Lab Group

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have surveyed treeline
locations on a global scale,

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particularly in this meta-analysis here.

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And they found that over half
of the treelines on slopes

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that they studied were
advancing consistent

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with warming trends,

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with the other half not
advancing significantly.

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So of course, the situation
is a little more complicated

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'cause treelines in general
are not all created equally.

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That same group identified

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four discreet archetypal treeline forms.

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There's the diffuse form
that's generally seen

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as a gradual decrease in the density

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and height of trees as one
increases in elevation.

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There's abrupt form that
forms a very hard barrier,

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or a hard line to growth
of tall, upright trees.

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An island form,

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which is represented by
small clusters of trees

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as one increases in elevation.

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And the Krummholz form,

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which it seems generally an increase

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of very small high class trees
as we go up in elevation.

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Now, the key takeaway here is

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that not all these forms are
driven by the same factors.

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The abrupt, island and Krummholz
forms are generally thought

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to be limited more by seedling mortality

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or adult tree dieback,

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where the diffuse form
is more growth limited.

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And so increasing temperatures as a result

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of climate change could drive an increase

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in the diffuse form more
so than these other forms.

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So keep this in mind as
we move through the talk,

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it'll be a very important point later on.

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Now, the Appalachian Mountain Club has

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sort of investigated treeline location

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and treeline shifts in the past.

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So in the '90s and the early
aughts, there was this effort

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to map alpine vegetation
communities on Katahdin

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and this is a product from that effort.

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However, the last couple
of decades have been some

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of the hottest on record,

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and so we all thought it
would be a very good idea

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to revisit this question
of shifting treelines

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and see if we could see
a climate change signal,

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and perhaps this would serve as a baseline

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for understanding the threats posed

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to very sensitive alpine vegetation.

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And so going into this particular project,

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we had two very well-educated assumptions.

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One being that treeline
locations are sensitive

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to changes in climate,

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and that changes in climate
itself can be modulated

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by topography.

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And so three goals that we had here

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for this particular project was

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to first quantify changes
in treeline position

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on alpine peaks in the Northeast

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over the last several decades

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using a spatial analysis approach.

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Our second goal being to assess
the demographic structure

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of trees at treeline,

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and the third would be
to determine variables

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that could potentially
explain treeline positions.

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And so, corresponding

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with these three goals
are three hypotheses.

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The first being that treelines
in the Presidential Range

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and Katahdin specifically
had shifted up slope

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over most recent decades
consistent with warming.

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The second that the diffused treeline form

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that I'd discussed earlier
is more sensitive to change,

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and we would pick up a signal of this.

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And the third is that
significant variation

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in treeline could be potentially
explained by measured

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and available climatological
and topographical variables,

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temperature, slope aspect, et cetera.

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And so as I move through this talk,

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each slide will be represented

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by one of these three hypotheses,

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and you'll see that in the top left.

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And so our study areas
include the Presidential Range

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sitting hear on the left,

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and Katahdin on the right and
their location in the region.

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These images are

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from the National
Agriculture Imagery Program

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or NAIP from 2018,

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and are false-color near infrared images.

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And as I move through the talk,

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whenever I show these
two ranges side-by-side,

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I'll denote them with P or
K just for clarification.

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And so to actually quantify
treeline advance we started

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with physical copies or
hard copies of images

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from both the Presidentials and Katahdin.

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The images were from 1978
for the Presidentials,

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1991 for Katahdin.

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These were scanned, geo and orthorectified

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and mosaicked into one image for both.

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From their treeline position

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it was manually delineated in ArcGIS.

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And for the old imagery,

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a total of 200 sample
points were randomly placed

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along this newly created feature.

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This process was repeated for new imagery.

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And from there we play sample points

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on the closest line
segment in the new imagery

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to old imagery points.

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So we have 200 paired points of old

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and new imagery, essentially.

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From there, we rasterized the features,

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multiplied the whole thing by
a two meter DEM of the region,

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and the mean difference between old

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and new sample points correspond

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to the change in treeline position.

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Additionally, for each sample point,

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we extracted the particular treeline form

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of that area given
information from imagery,

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from field photos and from
field notes taken by me.

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LGS GIS work was
supplemented with field work.

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A total of 5,400 meter
belt transects were put

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on the landscape,
encompassing the transition

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from closed canopy to open alpine areas

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through the transition of
treeline increasing in elevation.

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And for each of the full transect,

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for every tree that
intersected the transect line,

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species ID was recorded.

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Three classes of basal diameter going

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from small to large were recorded.

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Same thing for height and
the particular treeline form

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of the four discreet
forms I discussed earlier

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was accounted for.

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At each 20 meter interval,
a GPS point was taken,

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slope, aspect, elevation

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and soil depth to bedrock
using metal soil probe was

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also taken. (clears throat)

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To assess potential
drivers of treeline change,

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I extracted aspect, slope, and hillshade

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from a two meter DEM.

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These points here represent locations

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of HOBO Data Loggers recording hourly soil

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and air temperatures

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with the oldest being installed in 2007.

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These were used to calculate
mean monthly temperature across

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that time period and annual
accumulated growing degree days

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from which I interpolated
maps based on values

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from the HOBO Data Loggers.

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In addition, I was able

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to downscale annual precipitation data

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from a PRISM data source,

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and all of these served
to serve as predictors

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in a multiple linear regression

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with the amount of elevation
change in treeline serving

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as the response.

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The note, this was only
for the Presidentials.

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We did not have this
information for Katahdin sadly.

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So going into the results,

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last panel on the left is
showing all areas above treeline

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as they were from the old imagery,

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Presidentials on top,
Katahdin on the bottom.

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This middle panel is showing
all areas above treeline

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for the new imagery.

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It's kind of hard to see differences

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between the two just
looking at it like this,

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but this last panel here
is highlighting areas

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where tree cover has
advanced over recent years

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from old to new imagery.

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And in some areas it is
actually quite extensive.

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But looking just at the numbers,

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we did find that there was
an increase in elevation

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of treelines about 12
meters for the Presidentials

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and eight for Katahdin.

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When we convert this to a rate,

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this comes out to about
0.3 meters per year

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in terms of advance which
is very much consistent

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with other published values

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from slopes in the Northern Hemisphere,

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so that does track very well.

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This does lead to a small decrease

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in the area above treeline,

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which has potential implications
for sensitive alpine plants

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that do grow at these elevations.

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A very interesting result comes out

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when we look at soil depth data.

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So here I'm showing the mean number

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of trees per 20 meter
interval on our transects.

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So all trees between zero
and 20, 20 and 40, et cetera.

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As it relates to soil depth,

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we see a very strong decrease
in the number of trees

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as the amount of substrate decreases.

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And as we go up in elevation
along our transect,

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we noticed that soil depth
decreases very steeply.

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Basically, what we take away from this is

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that substrate is very, very limiting

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in terms of tree growth in these areas,

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which is not surprising given

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that a lot of these places
have no substrate at all,

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they're bare rock.

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And so while this may seem like
a very obvious relationship,

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I think it's very important
to highlight things like this

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as they serve as sort of the upper limit

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for which trees can advance.

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Looking strictly at treeline forms

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between those four forms
identified earlier,

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we see indeed that the diffuse form

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has experienced a greater change.

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Elevation shift in treelines
is more significantly sailed

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than the other forms.

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In order to cue and this is true

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for both the Presidentials and Katahdin.

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Looking at the demographics of treeline,

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we do find that tree
density does indeed decrease

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as we go up on our transects.

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This is not terribly surprising.

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Here, I'm showing a tree density

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between the four different main forms

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and between the three
basal diameter classes.

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We see that there really isn't

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that much of a difference
between the four forms

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in terms of basal diameter,

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but when we look at height,

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we do see some differences
start to emerge.

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For instance, in the Krummholz
form we see an increase

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of small high class trees

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as we increase in elevation
along our transects.

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In the diffuse form we see an increase

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in taller size class
trees or high class trees.

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And so I think these
results are very important

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because they sort of
serve as these indicators

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of different treeline
forms that can be assessed

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with very, very simple
transect based methods

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and could be very useful
for studies in the future

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that look at different treeline forms

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and how that relates to
changing treeline position.

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In terms of drivers of change,

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00:12:49,150 --> 00:12:54,150
our model explained a
small amount of variation

261
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about 15%, excuse me.

262
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And we found that both slope

263
00:13:01,030 --> 00:13:03,740
and growing degree days did
have significantly different

264
00:13:03,740 --> 00:13:06,540
than zero coefficients in this model

265
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with slope having a positive

266
00:13:08,830 --> 00:13:10,960
and growing degree days
having a negative coefficient.

267
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And when we actually plot that out

268
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for accumulated growing degree days,

269
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we find areas that are generally
cooler higher elevations

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with fewer accumulated growing degree days

271
00:13:21,900 --> 00:13:25,030
do experience a greater
change in treeline position

272
00:13:25,030 --> 00:13:28,700
as opposed to hotter
lower elevation areas,

273
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which potentially could indicate

274
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that these areas are already

275
00:13:32,800 --> 00:13:35,420
at a critical threshold
in terms of growth.

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00:13:35,420 --> 00:13:38,860
So any increase in temperatures leading

277
00:13:38,860 --> 00:13:41,700
to an increase in growing
degree days could serve

278
00:13:41,700 --> 00:13:46,540
to alleviate this
fundamental limit on growth

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as it relates to temperature.

280
00:13:48,250 --> 00:13:50,240
However, it'd be very
helpful for us in the future

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00:13:50,240 --> 00:13:53,950
to be able to assess how much change

282
00:13:53,950 --> 00:13:58,650
has occurred in temperatures
across different elevations.

283
00:13:58,650 --> 00:14:00,250
Currently, we don't have those data,

284
00:14:00,250 --> 00:14:02,200
but that would be very helpful to have.

285
00:14:03,060 --> 00:14:05,772
And looking at slope, we see an increase

286
00:14:05,772 --> 00:14:10,772
of treeline advance as
we increase our slope,

287
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which could just mean

288
00:14:12,490 --> 00:14:17,490
that a smaller distance
between our sample points

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00:14:19,320 --> 00:14:20,630
in areas with higher slope leads

290
00:14:20,630 --> 00:14:22,963
to a greater change in elevation.

291
00:14:24,980 --> 00:14:27,060
So to wrap everything up,

292
00:14:27,060 --> 00:14:29,090
in terms of our first
hypothesis, this was supported,

293
00:14:29,090 --> 00:14:31,220
we did find a significant upslope advance

294
00:14:31,220 --> 00:14:32,870
of treelines in these two ranges.

295
00:14:33,820 --> 00:14:36,370
For our second hypothesis,
this was also supported.

296
00:14:36,370 --> 00:14:37,930
There were greater upslope shifts

297
00:14:37,930 --> 00:14:40,230
of diffuse treelines in particular,

298
00:14:40,230 --> 00:14:42,320
which again, are more
limited to temperature

299
00:14:42,320 --> 00:14:45,563
and maybe more sensitive or
responsive to climate change.

300
00:14:46,500 --> 00:14:49,110
Secondarily, we also
saw an important role.

301
00:14:49,110 --> 00:14:52,210
Soil to depth is serving
as that upper limit

302
00:14:52,210 --> 00:14:54,023
for where trees can advance to.

303
00:14:55,040 --> 00:14:55,873
We also note

304
00:14:55,873 --> 00:14:59,650
that a demographic structure
can predict a treeline form,

305
00:14:59,650 --> 00:15:04,650
which can be useful as a
management and a monitoring tool.

306
00:15:06,860 --> 00:15:09,060
And our third hypothesis
was also supported,

307
00:15:09,910 --> 00:15:12,300
growing degree days climate
and slope typography,

308
00:15:12,300 --> 00:15:15,400
both together explain a
significant although a small amount

309
00:15:15,400 --> 00:15:17,090
of variation in treelines.

310
00:15:17,090 --> 00:15:19,510
And of course, it would
be helpful moving forward

311
00:15:19,510 --> 00:15:21,990
to understand the rate of change

312
00:15:21,990 --> 00:15:25,750
in particular climate variables to see how

313
00:15:25,750 --> 00:15:30,750
that itself affects the
amount of treeline advance

314
00:15:31,060 --> 00:15:33,650
that we've documented here.

315
00:15:33,650 --> 00:15:35,250
And so with that, I would just like

316
00:15:35,250 --> 00:15:37,260
to acknowledge the people,
agencies and funding

317
00:15:37,260 --> 00:15:38,480
that made this possible.

318
00:15:38,480 --> 00:15:41,960
The Sussman Foundation
and the NSF in particular.

319
00:15:41,960 --> 00:15:46,490
The AMC, Baxter State Park in particular.

320
00:15:46,490 --> 00:15:47,500
The US Forest Service.

321
00:15:47,500 --> 00:15:48,600
And of course,

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00:15:48,600 --> 00:15:51,790
I'd like to point out in particular Eben

323
00:15:51,790 --> 00:15:54,450
from Baxter State Park
and Georgia and Patrick

324
00:15:54,450 --> 00:15:56,000
from AMC that really helped out

325
00:15:57,315 --> 00:15:59,100
with accessing the HOBO data.

326
00:15:59,100 --> 00:16:01,340
And so with that if we have any time left,

327
00:16:01,340 --> 00:16:04,870
I'd be happy to take any
questions that anyone has.

328
00:16:04,870 --> 00:16:06,760
- It looks like we have a question already

329
00:16:06,760 --> 00:16:08,623
from Tim Howard in the chat.

330
00:16:09,937 --> 00:16:13,380
"That final figure looks
like you had treeline loss,

331
00:16:13,380 --> 00:16:15,350
downslope movement in some places.

332
00:16:15,350 --> 00:16:16,693
Can you comment on those situations,

333
00:16:16,693 --> 00:16:18,830
anything special about them?"

334
00:16:18,830 --> 00:16:19,770
- It's hard to say,

335
00:16:19,770 --> 00:16:21,510
I don't have any particular mechanisms

336
00:16:21,510 --> 00:16:22,393
as to why that happened.

337
00:16:22,393 --> 00:16:26,380
It didn't occur that much.

338
00:16:26,380 --> 00:16:29,973
I think disturbance probably
plays a role in those areas,

339
00:16:31,510 --> 00:16:33,603
if any major mechanism can be seen.

340
00:16:34,970 --> 00:16:37,430
There are some places where
there have been some rock slides

341
00:16:37,430 --> 00:16:40,340
that knock back growth.

342
00:16:40,340 --> 00:16:41,653
So if I had to guess,

343
00:16:43,360 --> 00:16:46,060
it would probably have to
do with something like that.

344
00:16:46,940 --> 00:16:49,870
- Yeah, I have a question,
it's Charlie Cogbill.

345
00:16:49,870 --> 00:16:51,530
- [Moderator] Yes. Go ahead.

346
00:16:51,530 --> 00:16:53,880
- Okay. Charlie Cogbill.

347
00:16:53,880 --> 00:16:57,850
I wonder if you've looked at
any of the historical imagery

348
00:16:57,850 --> 00:17:00,330
from our time previous to your...

349
00:17:00,330 --> 00:17:04,880
I guess, it's 1978 or
there's at least 100 here,

350
00:17:04,880 --> 00:17:08,760
very good chronology of
sequences of photographs

351
00:17:08,760 --> 00:17:12,030
both in the Presidentials and at Katahdin

352
00:17:12,030 --> 00:17:15,160
that could drive your change back

353
00:17:15,160 --> 00:17:19,287
into various previous trends.

354
00:17:20,600 --> 00:17:21,840
And there have been a few studies

355
00:17:21,840 --> 00:17:22,920
that have been done that shown

356
00:17:22,920 --> 00:17:25,366
that there's a lot of infilling

357
00:17:25,366 --> 00:17:29,860
of Krummholz in those photographs,

358
00:17:29,860 --> 00:17:33,040
but very little elevation will advance.

359
00:17:33,040 --> 00:17:37,510
- Right. I would certainly
love to look at those images.

360
00:17:37,510 --> 00:17:38,890
We did have someone approach us

361
00:17:38,890 --> 00:17:41,620
with some imagery from,
I believe it was 1943

362
00:17:43,600 --> 00:17:45,083
that we'd like to look at,

363
00:17:45,083 --> 00:17:46,710
but so far it hasn't been done,

364
00:17:46,710 --> 00:17:51,190
but definitely we're open
to looking at older imagery,

365
00:17:51,190 --> 00:17:54,563
and running the similar kinds of analysis.

366
00:17:56,540 --> 00:18:00,220
- Well, there is a gallery of photographs

367
00:18:00,220 --> 00:18:03,770
that have been accumulated
for the Franconia Range

368
00:18:03,770 --> 00:18:08,730
and for the Presidentials
within the US Forest Service.

369
00:18:08,730 --> 00:18:11,930
And there's ongoing work
on Katahdin right now

370
00:18:11,930 --> 00:18:15,920
about retaking photographs

371
00:18:15,920 --> 00:18:19,670
that were taken in the '60s looking

372
00:18:19,670 --> 00:18:21,220
at changes on the table land there.

373
00:18:21,220 --> 00:18:24,430
So let's keep in touch.

374
00:18:24,430 --> 00:18:25,720
- Yeah. for sure. (laughs)

375
00:18:25,720 --> 00:18:26,870
I'd be very interested.

376
00:18:28,260 --> 00:18:31,097
- All right. I think we have
time for one more question.

377
00:18:31,097 --> 00:18:32,657
Sarah Nelson asked,

378
00:18:32,657 --> 00:18:36,030
"Did you test Tmean on
the models or just Tmean?

379
00:18:36,030 --> 00:18:37,950
Sometimes Tmean is informative

380
00:18:37,950 --> 00:18:40,150
as it indicates freezing
nights, et cetera."

381
00:18:41,630 --> 00:18:44,197
- Yeah. I did, not only Tmean,

382
00:18:44,197 --> 00:18:49,197
but Tmax and then I did monthly
values as well for each.

383
00:18:51,100 --> 00:18:53,290
They're highly correlated with Tmean.

384
00:18:53,290 --> 00:18:56,083
So they weren't adding more
information essentially.

385
00:18:58,810 --> 00:19:00,160
Yeah, I did.

386
00:19:00,160 --> 00:19:02,923
And these very similar results uphold.

387
00:19:03,810 --> 00:19:06,460
- Okay. So it looks like
that's all the time we have.

388
00:19:07,870 --> 00:19:11,280
It sounds like if people
want to ask you questions,

389
00:19:11,280 --> 00:19:12,513
they can email you.

390
00:19:15,370 --> 00:19:18,010
And thank you so much for being here

391
00:19:18,010 --> 00:19:19,693
to talk at the conference.

392
00:19:20,770 --> 00:19:21,603
- Yeah. Thanks everyone.

393
00:19:21,603 --> 00:19:24,511
I'm more than happy to
respond to any emails.

394
00:19:24,511 --> 00:19:26,055
(clears throat)