Alder and nitrogen fixation-only native tree west of Rockies that does it

In searching out nitrogen fixing plants for my property I discovered that the red alder is the only large tree west of the Rockies which is capable of fixing atmospheric nitrogen. It is capable of producing more than 200 kg per hectare which compares favorably with legume crops such as soybeans and peas.

Because it is singular in my environment on Vancouver Island in its ability to provide this natural fertilizer I will favor it above all other native species. Soybeans don't want to grow in my environment while alder can't be stopped. In some parts of the world lightning is responsible for fixing huge amounts of nitrogen but we seldom have thunderstorms and therefore almost all of our nitrogen is acquired through biological means.

The north side of my large hugel beds are already lined with alder and with cedar. My plan is to use most of this cedar for building so that the entire strip along the north boundary is alder coppice. Within gardening areas whenever I need poles it would make sense to use this resource. I have several spots which are too wet for fruit trees but within close proximity of good fruit growing ground. Alder growing in these damp spots will fertilize the neighboring blocks with their annual leaf drop. In surveying the rest of the property I discovered that I have one ditch which is becoming rather full of organic material and most of it is alder leaves. There's about 1000' x 2' wide which will yield well rotted leaf litter. A much larger ditch and culvert are becoming clogged with organic debris. Most of the trees lining this seasonal waterway are alder so no doubt my dredging will provide top-quality soil. Since the water dries up completely every summer it won't really be dredging. I'll sling a giant slop bucket into the ditch with my crane and load up 500 pounds at a time. I may try to devise a bucket which can be filled as it is drawn forward since there is a 150 foot cable winch on the crane.

There is an area of about 3 acres which was completely clear-cut 11 years ago. It now contains many alder which are about 40 feet tall and they grow 6 feet every year. By the time I'm ready to farm this section there will be quite a bit of useful timber from the better logs and the low-grade stuff will provide as much as 100 tons of material for hugelkulture.

When I look across the river onto a vast area of government controlled tree farm it is abundantly clear that this forest is largely devoid of hardwoods. In searching out old government literature on tree farming there are large amounts of literature concerned with how to eradicate red alder. In newer and more enlightened government forestry pamphlets they advise forest managers to leave at least 200 red alder per acre in order to maintain adequate nitrogen for Douglas firs and other conifers. Studies have shown that tree growth in an 80 year rotation is severely limited by lack of nitrogen during the last 20 years of that rotation. Of course Douglas firs can live for 500 years but in these artificial tree farm situations those forests would barely grow for much of that time due to an acute lack of nitrogen.

There is also a lot of interest in using alder coppices for biomass energy in the Maritime Provinces, although it isn't the red alder (Alnus rubra). Alders tends to grow vigorously in disturbed areas that have poor soil due to association with nitrogen fixing microbes, and the result is a high yield, especially when coppiced or pollarded.

I wrote some praise of red alder. I have experimented with coppice. It tends to get fungal infections easily (which makes it fast for spawning logs or chips if you can keep the bark on). Also it doesn't produce a lot of primordia for forming epicormic shoots except at the whorls where terminal buds are located. So if you cut it low it dies (which is good for some applications), and if you cut it high, it sprouts at old nodes and than dies. So it is a good nurse crop and for biomass, but in my experience not coppice... Slide alder A. sitchensis or other northern shrub alders might suite better for coppice.

Just cleared a couple kept to boles for fuel and hugel and used the slash for mulch on a couple happy plums.

I don't know if this will grow in your area, but I believe the Mesquite tree is native to west of the Rockies, and certainly fixes nitrogen.

Alex

Mesquite is the champion of arid regions. The only way to get rid of it is to have other species prospering it, and thus, shading it out.

I've never heard of mesquite being grown anywhere near here but black locust has been introduced and apparently has a very good growth rate. I cut quite a bit of it when I lived in Ontario and it made me a little sick. Probably the 4% fungicide. But I'm definitely going to try some of it. I have one area bounded by a swampy patch which should contain any invasive nature.

I've widened the road and thinned out other alder. This produced about 2000 trees ranging from 3 to 7 inches in diameter which have been incorporated into hugelkultur beds. There were also a few thousand maple and cottonwood. Within a year, my total volume of standing alder will be back to where it was. It's a young stand which doubles aprox. every 2 years. Much of the remaining alder was competing with closely spaced maple and cottonwood which have been removed. Most young conifers have been removed.

Here in the PNW, red alder is the wood of choice for smoking salmon. It gives a nice flavor, without overpowering, like mesquite or hickory would.

...looks like Dale has enough quantities to smoke a few gray whales!

I will add that I use living red alder at the end of raised beds and near fruit trees, and dead trees in raised beds and as side forms...
But I haven't been successful coppicing close to the ground -- should I treat the stump to prevent rot or just cut 5' up or so?

The road is 5/8 of a mile in length and nature is constantly encroaching. About 1/3 of this young forest is alder. In thining it, I've cleared out plenty of maple and cottonwood which will allow the alder to flourish.

Looks nice Dale! My place has lots of wet bottomland where the alder survives the bestin groves -- but not with high survival rate. A few feet up the water table is mostly Red Cedar that doesn't give the alder much of a chance.
Whenever there is a freezing rain storm before the alder leaves drop, anything less than 10 years old is likely to fall over -- we had a bad one of these in Seattle about 15 years ago and it was mayhem for alder, plums and other young spindly trees... Looks like you're just as fine with alder logs as trees though!