… I came to see the owls as one of countless shapes the forest assumes, more than as an animal that resides in a forest. In this view, if the organism is removed from the old growth, it ceases to be a spotted owl and becomes just a brown, speckled, dark-eyed, meat-eating bird.

The feature that most exemplifies this awareness for me is the owl’s feathers. Unlike most raptors in this region, northern spotted owls don’t migrate south in the winter. They are here in rain and snow and cold. Yet they are not exceptional thermoregulators as one would expect of a nonmigrant facing a rainy, snowy Cascade Mountain winter.

The reason for this counterintuitive disparity is the old-growth forest, which buffers temperature extremes at both ends of the spectrum by as much as twenty degrees Fahrenheit in relation to adjacent clearings. The owls wear old growth like another layer of feathers. That is, their preferred habitat provides sufficient thermal protection, so that they do not have to expend energy growing as much down as they would need if they dwelled in open country.

The deep multilayered canopy characteristic of old-growth groves also intercepts enough snow to permit the owl’s preferred prey species – the northern flying squirrel – to remain active all winter long, feeding on truffle mushrooms on the open ground at the bottom of snow wells around the bases of the trees. With food and warmth (as well as many other life needs) literally covered by the old growth, the owl does not have to make a long flight to warmer climes at the onset of autumn.

Instead, the owl makes short flights in response to immediate conditions. Sun gaps on otherwise snowy January days draw them out from beneath sheltering midcanopy mistletoe umbrellas to ascend to high branches, where direct solar radiance can offer springlike warmth even during the coldest time of year. And in the heat of August, the owls are often found perched low in vine maples a few feet above a cooling creek in shady northeast- facing drainages. This behavioural thermoregulation and the incorporation of the forest itself into their meaningful physiology provide just two of many possible examples that demonstrate why efforts to reduce the spotted owl to a bird in a habitat represents extreme oversimplification.

from The Mountain Lion by Tim Fox, excerpted in Forest Under Story

Where does the forest end and the owl begin?

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While genecological studies suggest divergent selection on phenotypic traits for local adaptation to climate must be relatively strong (Howe et al. 2004; Savolainen et al. 2007; Alberto et al. 2013), population genetic studies suggest gene flow is high, as most widespread species show weak- to-moderate population differentiation (FST) for selectively neutral genetic markers (Kremer et al. 2012). How tree populations could diverge substantially for locally adaptive traits in the face of high levels of gene flow has been something of a puzzle (Savolainen et al. 2007). Theoretical modelling suggests that highly polygenic traits controlled by many co-varying loci of small effect can create phenotypic divergence under divergent selection despite high gene flow, but individual loci underlying such traits will have only weak divergence, and will be difficult to detect (Latta 2003; Le Corre and Kremer 2012; Savolainen et al. 2013). This genetic architecture presents a challenge for popula- tion studies to detect and adequately characterize local adaptation through genome scans

Aitken, S. N., & Bemmels, J. B. (2015). Time to get moving: Assisted gene flow of forest trees. Evolutionary Applications, doi:10.1111/eva.12293

Maybe I can solve a little piece of this puzzle with my PhD….

It is often assumed that forcing [for budburst] does not begin until after the chilling requirement has been met and this undoubtedly is what occurs naturally in boreal regions where extended periods of cold temperatures are never or rarely interrupted by warmer (forcing temperatures) until spring. We believe, however, that chilling and forcing can occur at the same time (in the temperature range where they overlap) and both systems are accumulating ‘‘time’’ over the dormant period. The systems involved in such accumulations (named the ‘‘memory of winter’’ by Amasino, 2004) are not understood.

From Harrington CA, Gould PJ, St.Clair JB: Modeling the effects of winter environment on dormancy release of Douglas-fir. Forest Ecology and Management 2010, 259:798–808.

The memory of winter

Inertia toward continued emissions creates potential 21st-century global warming that is comparable in magnitude to that of the largest global changes in the past 65 million years but is orders of magnitude more rapid.

From Diffenbaugh & Field 2013 in Science

Sentences to make your blood run cold