Old data, new tricks

When we picture scientists collecting data, we usually think of someone in a white coat mixing solutions in beakers or perhaps someone writing measurements on a clipboard in the middle of a seed orchard. But what happens after that data is collected and the papers are written?

Old Data, New Tricks on Research2Reality.


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.


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


Forest drought mortality

If you want to know more about the hotter droughts mentioned in Colin Mahony’s post a few weeks ago on forest management strategies under climate change mega-disturbances, you might be interested in this recent paper from Allen, Breshears, and McDowell on expectations for forest drought mortality.

Craig D. Allen, David D. Breshears, and Nate G. McDowell 2015. On underestimation of global vulnerability to tree mortality and forest die-off from hotter drought in the Anthropocene. Ecosphere 6:art129. http://dx.doi.org/10.1890/ES15-00203.1