Leaf to Landscape Project

Nathan Stephenson (USGS): So I came out here into Giant Forest in the
autumn of 2014 because we’ve been having this really severe drought and I was
convinced that the first place we would see the effects of drought on giant
sequoias were in the seedlings to my surprise they all looked pretty healthy
and I looked up into a big mature sequoia and I noticed that maybe half of
its foliage had died so pretty quickly we got a field crew
out trying to survey how much foliage die-back there was in giant sequoias
across the forest and realized that’s just one piece of the puzzle and we also
really needed to get the physiological information that you can only get by
climbing a giant sequoia. Still, the foliage die-back surveys and the
physiological work can only cover so much ground, how can you possibly expand
this out to the entire landscape? And, that’s by getting remote sensing. So in the end we call it the leaf to landscape project because it’s everything from
measurements on little clumps of leaves all the way up to entire landscape
measurements from remote sensing. Koren Nydick (NPS): Giant sequoias are just a really special and iconic species to the park. The park was established for the reason of
protecting giant sequoias from timber interests. Even though giant sequoias are
a relatively rare component of the forest they’re one that is just
extraordinarily important to people. You know they’ re majestic, huge trees.
The largest trees on earth, beautiful to look at with their red bark and black fire scars. One thing that I’ve really enjoyed and I think is a really critical part of this
project is just the collaborative nature. Working with UC Berkeley, Carnegie
Airborne Observatory, US Geological Survey. We’ve had funding assistance from
the US Forest Service and a graduate student from Stanford University. we’re
all working together you know with the National Park Service to make this
happen and each partner brings strengths to the table and no partner could do this alone. Anthony Ambrose (UCBerkeley): We took the maps that USGS had created
and went out and selected two sites showing signs of high die back two sites
showing signs of low die-back. Our team from UC Berkeley took the lead on coming
out here and doing the final tree selection and we rigged the trees and
got them all ready for sampling Wendy Baxter (UC Berkeley): We really wanted to make our measurements at the most severe point in the drought when the trees were the most
stressed. We came out at the end of August, early September. Over the course of two
weeks we climbed 50 trees twice. Once, before the sun came up. That provided sort of a baseline of the water status of the trees and then once in the
afternoon at the midday when the trees are losing more water and they’re more
stressed. Todd Dawson (UC Berkeley): The metaphor is that the water in the plant is almost like a rubber band and the lower the water in the soil and the more pull the atmosphere has on
that water it puts that rubber band under tension. The measurements that we
got in terms of the water status, the leaf chemistry, the leaf morphology water, content carbon concentrations… could be linked with airborne data. Greg Asner (CAO): So we flew over in May and we flew over again in August. And the kinds of measurements we
make are those that tell us about the height and the structure of the canopies
and also about the chemical attributes of the leaves in the canopies. One of the instruments on board our
plane has a unique capability of measuring the very subtle changes in
reflectance of the foliage in the canopy. So for example, water content in the canopy. The way that the spectrometer measures the reflectance of solar
radiation is very very sensitive to literally how many water molecules are
present. Emily Francis (Stanford): To actually figure out the exact amounts of the chemicals present in the leaves we’ve been doing different destructive
analyses to correlate the spectral information and the different wavelength
bands with actual chemicals that we’ve measured in the leaves. That creates a
model that we can then use to predict over the whole area that we’ve collected
hyperspectral data how much water or nitrogen is present in a given pixel of
the Giant Forest Making maps of species composition and the physiology and the
status of different types of species in the context of drought and climate
change, is useful to conservation and managment because it allows those folks
to make tough decisions on where to put extra protection where to apply tactical
management techniques August 2015, there’s a lot of forest in
California that looks to be severely drought stressed. And I’m talking about
forests that go from oaks all the way up to high elevation forests, conifer forest and
it’s in a very patchy mosaic across the State. As you get into the Sierras, you
see a repeating pattern of the lower part of the Sierras being the most
severely drought stress then it finally tapers off and you see the conditions
don’t look so drought stress at the very highest elevations. Of all the species on
the landscape in these lower elevation forests, sequoias did the best. The firs
did a lot worse, the pines did a lot worse, the cedars did a lot worse, the oaks are
doing a lot worse. The sequoias were the ones that hung in there the best of all the species. In 2014 when a lot of these tree shed their foliage that was actually a quite effective mechanism, an adjustment of the trees leaf area to
minimize how much water they’re losing to the atmosphere in order to maintain a
favorable water status. So why we think maybe giant sequoia is so resilient to drought may really be embedded to their great longevity. They’ve been
around for millions of years and of course have gone through many episodes
of climate related natural selection. We’re beginning to think that the giant
sequoia groves are these little enclaves where for maybe other reasons there’s
just more water and more reliable water and maybe that’s coming from even outside
grove boundaries but being channeled through cracks in the granite or something like that. It’ll be really interesting to start putting all these
pieces together Giant sequoia groves in and of
themselves could be a climate change refugia. A place on the landscape that is
relatively buffered from climate change. The big question, is are they going to be
able to make it through these new kinds of bottlenecks and be able to persist in
the ways that they have for millions and millions of years? Stay with us as we develop the story, as we get both a better answer of what’s going on out
there and what that might mean for the future


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