Pioneering Soil-Enhancer: Red Alder

Red alder grows in pure stands, as shown, or in mixed forest settings

Red alder (Alnus rubra) is the most common deciduous tree in the Pacific coast forest. It is not a long-lived tree (usually about 60 yrs, rarely over 100), and despite rapid growth while young, these trees never reach (40 m/131 ft) the sizable proportions of the conifer stands surrounding them. However, the Red alder possesses a capacity that no other tree on the coast has.

Red alder is the only tree west of the Rockies capable of fixing atmospheric nitrogen. Red alder develops an extensive, fibrous root system, with root nodules that fix nitrogen from the air. The nodules are a symbiotic association between the tree and actinomycete, a large group of bacteria that are responsible for the characteristic "earthy" smell of freshly turned, healthy soil.

Male flowers are long, drooping, reddish catkins, and female flowers
are short, woody, brown cones.

In this 'everyone wins' relationship, nodules are formed where bacteria infect a growing root. Then the alder supplies carbon compounds to the bacteria, and the bacteria convert nitrogen from air into a form the tree can use.

When leaves or roots from the host plant decompose, available nitrogen increases resulting in richer soil and better growing conditions. There is evidence that this relationship is so beneficial to the alder that its roots produce a substance that encourages the bacteria to set up shop. Alder is also associated with mycorrhizal fungi which helps enhance nitrogen fixation.

Alder along Carmanah River, Carmanah Park

After the soil bacteria community is established, Red alder seeds germinate well on freshly disturbed, nitrogen deprived land such as slide areas, road cuts, river flood plains, or clear cut areas that have had the slash burned. It is an aggressive pioneer species, and grows quickly as a seedling in wet soils.

Height growth of the Red alder seedling can be as much as 1 m (3.3 ft) or more in the first year. Giving the Black cottonwood a run for its money, maximum annual height growth of more than 3 m (9.8 ft) a year can be achieved by 2- to 5-year-old alder seedlings. Indeed, after the Black cottonwood, the Red alder is the second fastest growing tree in the coastal forest.

Associated conifers have much slower juvenile growth, but they sustain height growth years longer than alder. On an average site, both Douglas-fir and red alder can attain the same height at 45 years. Beyond that, Douglas-fir far surpasses Red alder in height. Once overgrown by the conifers during forest succession, the sun-loving red alder will die back, leaving a legacy of rich soil.

Red alder on their way for another season of nitrogen-fixing, soil-enriching growth

Besides its usefulness to soil quality, and its visual appeal, Red alder is also a commercially harvested species along the coast. It is used in the production of solid wood products, such as furniture, cabinets, case goods, and pallets; composite products, including plywood; and fiber-based products, such as tissue and writing paper. It is also used for firewood, and is the wood of choice for smoking salmon.

Although for a while Red-alder, like Black cottonwood, was seen as a nuisance tree and cut out of mixed stands, we are now realizing the soil-healing properties this tree has. Because it can increase soil nitrogen and organic matter, it is being increasingly used to rehabilitate disturbed sites, or prepare areas for conifers such as Douglas-fir.

The Red alder is an important part of the Pacific coast forest ecosystem. Look for them along streams and rivers, as well as lake shores. Disturbed sites will also have stands of alder pioneering the new forest. Watch for a medium-sized, deciduous broad-leaved tree with a narrow rounded crown, straight, slightly tapered stem, and smooth, light gray bark.

Big Leaf Maple

A magnificent hardwood species is mixed among the monumental softwoods of the Pacific forest. The Big leaf maple (Acer macrophyllum) is a coastal broad-leafed tree which grows predominately in the southern coastal western hemlock biogeoclimatic zone. They grow in a narrow strip along the ocean from Alaska to California. Big leaf maple live an average of 200 years with 300+ not unheard of, and reach heights of 34m with a crown of equal width. While conifers are king (or queen) in the Pacific forest, the overlooked Big leaf maple is an important member of the court.

"It is so ubiquitous that many people, Douglas-fir tree farmers in particular, consider Big leaf maple to be a common and bothersome weed," says Mike Dubrasich, tree farmer, "but Big leaf maple is easy to grow, and on most sites it will out-grow any other native tree for the first twenty years."

Big leaf maple's preferred habitat is close to rivers or streams on gravely, moist soil, but it will also grow in dry areas. These trees can withstand temporary flooding and do well in nutrient-rich floodplains. The tree pictured is on the floodplain of the Sooke River, and grows in a field unchallenged by competitors. A bicycle is shown to provide scale.

When Big leaf maple grows in a forest, shaded by other trees, it develops a tall bole with no branching until 1/2 - 2/3 of the way up. Then a small crown grows above the single large trunk. These trees are increasingly valued in the forest industry since the single bole can provide larger pieces of wood.

Growing out in the open the maple's crown reaches its maximum  spread, and the bole splits into a multiplicity of branches just a couple of meters up.


The Big leaf maple featured here is in Sun River Nature Trail Park, a narrow park that stretches along the west bank of the Sooke River. It is accessed by a trail head off Philips Road, itself a gateway to big trees and beautiful vistas of the Sooke River valley and surrounding forest-cloaked hillsides.

The rough trail passes through a riparian forest of large Sitka spruce, Douglas fir, Western red cedar, and Hemlock. This flood-prone forest also has broad-leaf trees such as Red alder and Big leaf maple, and harbours bear, cougar, owl, and slug. Spawned out salmon fertilize this forest every fall. Valley bottom forests of Vancouver Island are the richest environments on the coast and the largest trees grow there. These valley bottoms are now mostly logged out.



Typical of a non-shaded maple, this tree has an expansive crown. Branching starts low on the trunk and spreads in all directions forming a massive green umbrella that almost touches the ground all the way around the perimeter. Big leaf maples can grow such a dense canopy of frizbee-sized leaves (up to 61 cm including the stalk) that only 1 to 2% of the light falling on the tree reaches the ground below. On a hot sunny day it was several degrees cooler in the shade of this glorious moss-covered giant. After some hard biking I was appreciative of the air conditioning. The soporific sun was held at bay and I felt revived.



Under the canopy of this tree were small tufts of grass and not much else. The huge leaves, when shed in the fall, will smother anything that tries to grow below the circumference of the crown. Also falling to the ground is a variety of epiphytic growth consisting of plants that live on other plants, but derive their nutrients from rain and the air, not the host.



Luxurious rain-soaked mosses adorn the branches of Big leaf maple. Lichen, as well as licorice ferns are also growing on the trees. Often this growth is so abundant that it weighs more than the leaves of the tree. When epiphytic growth falls to the ground it fertilizes the tree in exchange for providing a place to grow. Big leaf maple is a soil building species, and like Red alder, it improves the soil where it grows.

Although I do love standing, living trees, Big leaf maple is increasingly seen as a commercial product. It has a fine grain and is desired for furniture and instrument making. The market for figured wood (wavy, quilted, curly, flamed...) is growing as wood workers and instrument makers come to value this unique wood.

The Glimer Wood Company in Portland, Oregon sells specialty woods including Big leaf maple for instrument building. Their website shows chunk after chunk of amazing one of a kind blanks ready to be made into guitars, violins, mandolins and ukeleles. Unfortunately, instrument woods most in demand are those from trees older than 150 - 200 years. The wood from such trees is clear of knots with an even fine grain, and provides the resonance instrument makers and players alike enjoy.

As a guitar player, and tree lover, I experience some guilt about owning the remains of old growth trees such as Sitka spruce and Big leaf maple. The classical guitar shown here has a spruce soundboard and uses figured maple for the back and sides. The back is a book matched piece. This means that the maple blank was cut in half and "opened up" to show matching patterns. Looks beautiful, sounds great. Probably came from very old trees.

Trees are such a giving, and useful species. It is hard to imagine life without them. Is it even possible for large modern, developed societies to exist without trees? Forests are massive contributors to ecosystems around the world, providing us with benefits that can not be fully calculated, or replaced. Trees are also large contributors to economies around the world. I love the trees, but I love my guitars, too. Here is one group that is trying to resolve issues around dwindling supplies of instrument woods. Perhaps a donation will help soothe my conscience.

Not all uses of the Big leaf maple require killing them. Like its more famous eastern cousin, the Sugar maple (Acer saccarum), the Big leaf maple can also be used for making syrup. The sugar concentration in Acer macrophyllum is less than in Acer saccarum, so more sap must be collected to produce the same amount of syrup. At the BC Forest Discovery Centre in Duncan, one can learn all about Vancouver Island Big leaf maple syrup making during the Bigleaf Maple Syrup Festival in February.

Today I will honour the generous Big leaf maple by spending some time beneath the shady branches of the tree featured above meditating on the gifts it bestows, living or otherwise. When I get home, I will compose a song about this harmonious hardwood, then perform it on the guitar that owes its life to the ultimate sacrifice made by individual, old trees. Thank you, trees.