The Daily Bucket is a nature refuge. We amicably discuss animals, weather, climate, soil, plants, waters and note life’s patterns.
We invite you to note what you are seeing around you in your own part of the world, and to share your observations in the comments below.
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First week of October 2018
Pacific Northwest
We have three native maples in the Northwest, here in coniferland. Maples are among our few deciduous trees, and here as elsewhere, their foliage is turning color and dropping now. One of our maples, our largest and most important ecologically, has recently begun dying across the region. No one knows why exactly but clues are emerging, and it doesn’t look good.
Let’s take a look at the Northwest native maples, what they’re doing in my home area right now and what’s on the horizon.
Douglas Maple (Acer glabrum)
Elsewhere these are called Rocky Mountain maple, likely because they do well in cold temps and dry soil, but here we call them Douglas maples. They are fairly common where I live in the San Juans due to our very low annual precip compared to most of maritime Washington. These are moderately small trees. Foliage turns shades of orange and red. They are at the end of their leafy stage right now. Another couple of big windstorms and they will be bare until next spring.
Vine Maple (Acer circinatum)
Much smaller and more shrubby in habit, with multiple and curvy trunks, Vine Maples prefer a shady understory. They also like damp soil which is why they are rare in my area — too dry. I planted one in my yard for sentimental reasons having grown up in a wetter part of the state where Vine maples are abundant. It’s done pretty well, considering. Like the Douglas Maple, its foliage has turned orange and red. My Vine Maple is holding onto its leaves a bit later than the Douglas, but it’s more sheltered from the wind.
I was looking at the pattern of color change on individual leaves after our convo in a recent Bucket about the BigLeaf Maple dieback. “Leaf scorch”, ie turning color on the margins, has been identified as a symptom of BLM dieback, but leaf scorch is also caused by drought. Douglas and Vine maples have not been affected by whatever is killing the Big Leaf maples, but I’m seeing leaf scorch in this Vine maple foliage, hence drought-caused. This little tree did better than usual this year, held onto its leaves longer, probably because my garden helper cleared out brambles that were competing for soil moisture. But dry soil is a stressor for Vine maple, especially one out in the open like this.
Big Leaf Maple (Acer macrophyllum)
Big Leaf maples grow much larger than the others and are major iconic Northwest trees, shady in summer and draped beautifully with brightly green epiphytic mosses and ferns in winter. Big Leaf maples require fairly damp soil, so they are only common where I live in the wettest part of the county. Their geographic range is along the narrow coastal maritime zone of Western states and in the Sierras.
Big leaf is no exaggeration. These leaves are gigantic. When I was a kid I used to make containers out of them in a pinch by folding up the pointed ends and tying them together with the stem. I could carry a whole lot of blackberries or huckleberries on my way home down the lane from the bus stop in fall. Big leaf maple leaves turn color — yellow and brown — and drop later than the other maples. Below a mature tree, kids can bury themselves completely in raked piles of their crunchy leaves before the heavy winter rains turn them to layers of mush.
Taking a good look at my nearby BigLeaf maple, I have not seen any of the signs of BLM dieback, which are small, pale green or scorched leaves, or none at all, with crowns dying completely. I’m relieved to see big, deep green leaves just starting to turn right now.
Maple fruits — “helicopters”, aka samaras — are produced abundantly by all three maples and are welcome fall food for wildlife. Big Leaf maples affected by the dieback generate many more fruits than usual. I looked on and below my tree and saw some samaras, but also birds eating them.
So my trees are still safe from the dieback. So far.
But Big Leaf maples across the region elsewhere are dying, and the problem is accelerating. First noticed in 2010, researchers with the US Forest Service, Washington DNR, and the University of Washington have been testing affected trees for the causal agent. Nothing has been found pathologically:
- There are lots of Pythium ssp. (a common pathogen) out there but the most common are not pathogenic to bigleaf maple in soil tests.
- There is a small amount of pathogenic Phytophthora associated with declining trees, but not enough to be the causal agent across the landscape.
- Armillaria root disease and decay is contributing to some of the tree dieback, but not all of it.
- The wilt disease Verticillium is not widespread and was not found in any of the samples in Washington.
- Stem cankers caused by fungi like Neonectria or Nectria are sometimes present, but not enough to be causing the widespread damage.
- Ganoderma, a causal agent of heartrot, is present in some cases but also is not causing widespread damage, though there are lots of foliar fungi out there that can cause discoloration in leaves. — DNR dnrtreelink.wordpress.com/…
Investigation is now oriented toward environmental factors. Affected trees are more likely to be in locations that are warmer and drier, and closer to roads and developed sites. Stressed trees are then more susceptible to pathogens.
Climate change is making our usual summer dry season longer and dryer. This year the May to September season had record low precipitation in western Washington. Anecdotally, some of us are noting fewer foggy days in late summer, which might be adding to drought stress. Is climate change in combination with other localized environmental conditions becoming lethal to this iconic Northwest tree? BIg Leaf maples have an important ecological role in our forests: they provide food in seeds and foliage, flowers to pollinators, nesting for ducks and woodpeckers, roosting for many birds and mammals, support for epiphytes. Their absence would be a serious loss.
I’ll continue watching for dieback symptoms. Anyone else in their range — are you seeing effects in your area?
(Here are some more resources with information about this tree and Big Leaf Maple dieback:
News Tribune article www.thenewstribune.com/…
USDA Forest Service www.fs.fed.us/...)
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Overcast with sprinkles today in the Pacific Northwest and 56°. We’re alternating between sun and cloud and rain these October days.
What’s up in nature in your area today?
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