Quercus lobata growing on Table Mountain
For those who wander looking for wildflowers during California’s springtime, I suspect this tree will be immediately familiar. It is the valley oak or roble that grows near the main parking lot to the exceptional North Table Mountain Ecological Reserve, photographed seven years ago in early morning light.
About 200km (120 miles) to the west of this tree, the current tallest oak in North America can be found. That particular valley oak is 47m (153 ft.) in height. Historically, white oaks (Quercus alba) in the old-growth forests of West Virginia, like the Mingo Oak, exceeded 60m (over 200 ft.).
Although widespread in distribution within California’s central valleys and foothills, Quercus lobata is listed as Near Threatened in a 2017 IUCN Red List Assessment. Habitat fragmentation and agricultural / urban expansion are listed as the main causes of its decline, but habitat shift and contraction due to climate change are also considered as part of the assessment process; it is conservatively predicted that there will be a 27% decrease in suitable habitat for valley oak by 2099.
One of the strategies to deal with declining populations is restoration. I am not a restoration ecologist, so others will correct me in the comments, but my understanding of the modern best practices for restoration is to bulk up local populations using seed sourced from those same local populations. The notion is that localized populations may have higher frequencies of genes (or expressions thereof) that foster local adaptations to the environment; the introduction of genetic material from non-local populations may actually work against future generations in that region.
Post-dating the IUCN assessment is this 2019 paper: Adaptational lag to temperature in valley oak (Quercus lobata) can be mitigated by genome-informed assisted gene flow (Browne et al. in Proc. Nat. Acad. Sci.). The authors state up front:
We show that an ecosystem-foundational species in California, valley oak (Quercus lobata), is already mismatched to current temperature and will likely experience further declines in growth rates as temperatures rise over the next century.
The authors propose another consideration for those involved in restoration: genome-informed assisted gene flow. To summarize: in order to mitigate climate change’s effects on a local population, it isn’t enough to bulk up numbers of plants using locally-sourced seeds; instead, informed introduction of genes from plants that are best-suited for warmer temperatures may have to become a standard conservation practice in restoration (at least in some instances).
Great photo. It has a 3d quality as if image stacking was used. Or, was it simply the magic of light?
Hi Mark, just the magic of early morning light!
Although, the direction of the clouds seemingly radiating to the upper corners might also lend some of that visual effect.
Oh, and I’ll add: bright tones bring things to the forefront, dark tones recede, so the tree has another layer of dimensionality because of that.
Hi Daniel,
When encountering isolated mature trees I am always interested to understand why it is there, why there are no seedlings or juvenile trees around. Is grazing the only culprit? Are there any other trees that can survive the ecology of this area and the grazing?
Who is responsible for grazing? Any cattle involved?
Best from Arboretum Wespelaar
Philippe de Spoelberch
Hello Philippe,
Yes, exactly as mentioned by Carrie below–this area is heavily grazed by cattle. I think those are even cow patties in the lower right corner of the photograph on the grassy band.
There are other woody species in the area, but I think one needs to visit the heavily-sloped areas and ravines to encounter these.
For others reading, some additional factors in seeing isolated mature trees in landscapes could be: fire regime, fruit predation, snow/frost/wind regime (consider the top of the tree line on mountains), and soil disturbance. I don’t think that’s a comprehensive list, though!
That is GLORIOUS!
Hi Philippe,
Yes, this area is heavily grazed by cattle.
What a beautiful image Daniel! (it will grace my desktop OK?) As a simple layman information may be beyond my grasp but I will study it. Of course at my age I’ll forget it. 🙂
You’re welcome, of course you can use it for your desktop.
We all do what we can, no matter the age!
A stunning photo of a magnificent tree – thank you for gracing our in-boxes with these marvelous photos during these worrisome times! Something to look forward to every day!
What a wonderful exemplar of the strength of oak trees with those massive horizontal branches.
Daniel,
Thank you so much for continuing Botany POD all these years. I just can’t express how much I appreciate these beautiful images and descriptions of plants from all over the world. I live in Hawaii, which of course has plenty of beautiful tropical plants and trees but I love seeing what grows in other places. I have learned a lot over the years from your postings and continue to look forward to receiving them. Thank you for all that you do!