12/4/15

Scouring coastal Alaskan forests : a journey through the past (Part 2)

Two wonderful weeks of hard work on the Kodiak Archipelago resulted in a truck loaded with 350 silica-dried needle samples and about as many tree cores from Sitka spruce forests. Happy and satisfied with the amount and spatial distribution of these tree samples, I embark on the ferry full of confidence about the second part of the trip: Sampling on the Kenai Peninsula.

Kodiak Island from the ferry

Bye-bye Kodiak!

Back on the continent, my main objective is to find old-growth forests of Sitka spruce and apply the same sampling design. By doing so, I will be able to compare the genetic make-up of a long-established forest to the young forests of the Kodiak Archipelago. I chose the Kenai Peninsula because it is the most likely origin of the trees that established on Afognak and Kodiak Island.

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Just to remind you the general direction of Sitka spruce expansion.

This second chapter to the Alaska journey will provide the essential baseline data for my project and will help answering the following questions:

 

To what extent is population expansion linked to a drop in genetic diversity?

Are trees at the front of expansion experiencing higher levels of inbreeding than trees in core populations? Are they subject to lower levels of selective pressure?

Do deleterious / advantageous mutations spread more easily during population expansion?

Team number 2 is waiting for me in Anchorage: Jon and Vincent, fresh out of the plane. Two highly motivated Aitken Lab members. Two masters of tree-spotting, mushroom-picking, blueberry-gathering, and wild-cooking. Already on the first day I am tempted to re-name them Witty and Cheeky. But they ended up being “Yonathaaan” (with the strongest German accent you can adopt) and “Young Padawan”.

Jon and Vincent.

The crème de la crème of mushroom pickers.

While the difficulty on Kodiak was to get to big trees before the loggers, the difficulty on the Kenai was to get to big trees before the bark beetle. A devastating outbreak in the 1990s left very little of the pristine, old-growth spruce forest I was looking for. A lot of remaining old-growth lies in a thin strip of wet lowland crunched between the sea and the gigantic Harding Icefield, an impossible target for us and Bean, who likes roads more than glaciers and waves.

But thanks to the help of Ed Berg, bark beetle expert, John Morton, wildlife biologist, and our flawless determination, we finally manage to find beautiful, road-accessible stands of pure Sitka or mixed Sitka spruce-western hemlock forests around the Seward Inlet.

Kenai sampling areas

Sampling locations around Seward

After stalling a few times due to excessive scenic landscapes, we’re back in the coring-trunks-and-snipping-twigs business! We keep the same sampling scheme as on the Kodiak Archipelago: collecting equal numbers of tree needle and tree cores among 4 levels of forest structure (see previous post for details) in several locations, and keeping a distance of at least 50 m between sampled trees. The most striking difference in forest structure with Kodiak Island is that there is no “proper” tree of level 5. For sure there are very large trees (winning DBH: 138cm!), but none of them shows signs of open-growth (large lower branches). To me, this confirms that the canopy on the Kenai is way older than the oldest trees, unlike the canopy of Kodiak Island.

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On the left, a Kodiak #5. On the right, a Kenai #5. Note: the scale on both pictures is represented by a normal-sized human being.

Although finding stands with no sign of recent disturbances was a real challenge on this part of the field trip, we managed to find four suitable sampling areas around the Seward inlet and added 197 trees to the collection. Early August, more than six weeks after having left from Vancouver with Ian, Bean and Jethro, it is time to return home. With a few kilometers added to Bean’s odometer, new or reinforced friendship bounds, beautiful memories of wild landscapes, a total of 550 tree samples and exciting prospects for my PhD research, I can’t wait to process all the data…. and go back on more adventures!

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A last evening up North, somewhere on the Alaska highway

11/26/15

Sierra McLane and Sally Aitken in The Walrus

Aitken-ites in The Walrus talking whitebark pine and assisted migration.

[N]ear the end of McLane’s whitebark planting trip in BC, it started to snow. Parked in whiteout conditions on a mountaintop, with no views to admire, McLane pulled a fourth layer over her down coat, grabbed her fingerless gloves, and braced herself for the whipping wind. Each day, as the temperature dropped, her unplanted seedlings became less likely to make it through the winter, leaving them in as much danger as ever and us no wiser for it. Crawling through ankle-deep snow, McLane spent her days scraping out holes with a tent peg and pushing the sprouts into the frozen dirt with her bare, numb fingers. Then, as now, the experiments had to go on. “We’re in a race against time,” she said.

11/24/15

The Aitken lab goes to Saturna

What does a group of scientists and tree enthusiasts do when they go on a retreat? They go on hikes (or runs, paddles or swims), they look at trees, plants, landscape features  and wildlife. They cook and eat good food, and play board games at night. They also discuss trees, politics, philosophy and everything in between. In short, they have fun!

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Warm Kale Salad with Lemon Parmesan Dressing:

Warm Kale Salad with Lemon Parmesan Dressing

Thai dragon bowl soup:

This soup recipe comes from the Rebar modern food cookbook, by Audrey Alsterberg and Wanda Urbanowicz (2001), page 145. Since I don’t own copyrights to this book, I can’t just post the recipe, but I encourage you to find this book in your library, or go eat the soup in the Rebar restaurant in Victoria, BC. I will tantalize your tastebuds by mentioning some of the ingredients I used (I don’t follow recipes exactly): ginger, chili pepper, garlic, soy sauce, fish sauce, lemon, sugar, coconut milk, tofu, rice noodles, snow peas, tomatoes, scallions, bok choy, cilantro, basil, oyster mushrooms. Spinach would also work really well.

11/24/15

How fast did Pinaceae ranges move in the past?

A few years ago, Alejandro Ordonez and Jack Williams published a study comparing the speed of range migration to the speed of climate change during 6 periods of change in the last 16,000 years. Jacquelyn Gill described the paper with a bit of context.

 They found that northern (leading) edges expanded more rapidly than southern (trailing) edges, and that tree velocities were as fast or faster than the climate velocities for the same interval. They found that not only were tree range shifts  paced by climate change in general, but that biotic velocities were faster when climate change was more rapid. Populations at the leading edge were more sensitive than the trailing edge to climate change, suggesting that expansions were climate driven but mortality at the trailing edge was affected by non-climatic factors like biotic interactions. As Ordonez and Williams note, their velocity estimates (-1.7 to 2.7 km/decade) are on the low end of previous pollen-based estimates (1-10 km/decade), but slightly higher than those estimated by McLachlan et al. (<1km/decade). Meanwhile, Loarie’s climate velocity estimates for the next century are higher, ranging from 0.8 km/decade to 12.6 km/decade. To complicate matters, species have been documented to reach average velocities of 6.1 km/decade or 16.9 km/decade in response to the climate change observed in the last few decades.

This is relatively encouraging as far as expectations for trees under current climate change – ranges often expanded northward as fast or faster than the climate changed, and stuck around for awhile in the trailing edge. So far, though, it doesn’t look that rosy this time around.

Their dataset included 30 plant genera, mostly woody angiosperms. Since we mostly work on Pinaceae in the Aitken lab (but see here), I pulled out those genera for a closer look.

These graphs show latitudinal biotic velocity vs. latitudinal climatic velocity. Positive values are northward movement and negative values are southward. In general, the biotic velocity is ahead of the climatic velocity, though the fastest they seem to go is about 2km/decade – not exactly a rapid clip.

I wonder what’s going on with the negative climate velocities at the southern range edge. If climates to the south became more favourable, why would the range shift north?

 

The data was published with the paper, but as a pdf. A. Ordonez was kind enough to provide me with an excel copy. Code used to generate graphs can be found here.

Zhu, K., Woodall, C. W., & Clark, J. S. (2012). Failure to migrate: Lack of tree range expansion in response to climate change. Global Change Biology, 18(3), 1042–1052. doi:10.1111/j.1365-2486.2011.02571.x

Ordonez, A., & Williams, J. W. (2013). Climatic and biotic velocities for woody taxa distributions over the last 16 000 years in eastern North America. Ecology Letters, 16(6), 773–781. doi:10.1111/ele.12110