One of my favorite trees is dead. It hasn’t sprouted a new leaf in over four years and yet, it’s the most active tree in the yard. From my dining room window I watch Pileated Woodpeckers (Dryocopus pileatus), Northern Flickers (Colaptes auratus), Cooper’s Hawk (Accipiter cooperii) and other smaller birds stop by for a perch or a peck.
This Alder (Alnus rubra) likely died by a fungal disease spread from the aphid infestation that plague it. There’s also an ant colony. While they don’t use little whips to herd the aphids about in their duties, I do suspect that symbiotic relationship of overseer and worker. (Herding Aphids: How ‘Farmer’ Ants Keep Control Of Their Food — ScienceDaily)
Alder trees are short lived in comparison to other trees with an average age of around 40 years. They are fast growers and prolific seed spreaders, much to the frustration of my neighbors with more manicured yard. The nature of a tree’s genome delegates whether it will be fast and widespread or slow and methodical. A mixed forest provides many benefits to the trees themselves and not just the habitats they create. Here in the Pacific Northwest, Alders help fix the nitrogen in the soil aiding the growth of Douglas firs. (The effects of red alder on growth of Douglas-fir (fs.fed.us))
As far as dangerous trees goes, alders are least likely to kill you. It’s common for alders to lose their heads in sections of 4-8ft over time. Easier to avoid than a 80-100ft Cottonwood (Populus balsamifera L. ssp.) coming down like a giant’s toothpick. When alders are allowed to lay where they fall they break down releasing nitrogen in the soil for other flora and nesting burrows for insects. These insects in turn become nummy snacks for other invertebrates, herps*, and mammals and occasionally homes for them as well. Ah, the simple life of a garter snake (Thamnophis sirtalis), to have your home warmed by the southern sun with your meals walking ripe for the taking.
If you’ve got a dead or dying tree on your property I would like to encourage you to consider alternatives to complete removal. If the tree is a low activity area away from harming people and building consider leaving it be. If it does pose a threat, have it taken down only so far as to reduce the threat it poses without removing it completely. You should be reward by the visit of birds. In my area, people are excessive land groomers. They dispatch tree companies post haste towards trees considered unattractive and then wonder why the woodpeckers pound on their houses. I’m not encouraging you to have an entire graveyard of trees, just one or two. Do it for the birds!
The Hidden Life of Trees: What They Feel, How They Communicate – Discoveries from a Secret World By Peter Wohlleben
Bugs Rule! : An Introduction to the World of Insects by Richard Redak and Whitney Cranshaw
Winter World: The Ingenuity of Animal Survival by Bernd Heinrich