Friday, April 20, 2007

Restoring the Redwoods

A few years back I had the pleasure of working at an estate nestled against open space on Mount Tamalpais, where the main focus was to create natural gardens for the children of the family and support the local wildlife. One of our big projects was to restore the habitat of a redwood forest along a creek and to invite native species back, including the Giant Pacific Salamander and the endangered California Newt.
The work had been in progress before I joined the team, where they had connected up several sections of the creek that had been disrupted by a fire road. At the stage where I joined the project, we freed the trees and tall shrubs along the creek from the grip of algerian ivy and planted native plant species such as Oregon Oxalis, Huckleberry, and Western Sword Fern. The plants started to establish themselves and in time the forest became lush and green, but there were no amphibians. We would see them just on the other side of the fence, but they never ventured over to our side. We wondered why.
We practiced only organic methods here at the property, and taught seminars in the community and the Greenwood School about gardening and design working with nature. One big push was for the use of compost to improve soil quality and drainage, eliminating the need for inorganic fertilizers and improving the overall health of a garden. Every spring I joined the crew with the wheelbarrow, and we would clear the leaves from the previous year and mulch every inch of the property, including the forest.
Then one year I took an Integrated Pest Management course at College of Marin. I learned about soil pathogens and their transmission, and that unfinished compost could spread disease. Up at the property I began to clearly identify that what we'd previously thought were gophers killing all our maples was not an animal, but a soil-born fungal infection from family of diseases collectively known as wilt. More investigation revealed that our practice of mulching with unfinished compost in combination with pruning had allowed these fungi to infect our trees through the wounds. It was everywhere we looked, and each time we cut into a dead branch the blue streaks of diseased tissue revealed wilt in another precious tree.
We promptly haulted our mulching practice until we could find a more reliable source for our compost. Remarkably, many of the trees recovered. During that time we let the forest cover itself in the rust colored duff of fallen redwood leaves. We debated if the duff would smother the young seedlings of the trilliums and other tender plants. Instead, the forest seemed to flourish. And by this accident, one day we discovered salamanders in the largest pool of the creek, basking in the sun that filtered down through the trees.
The one thing our forest had lacked was fallen leaves.

Integrated Pest Management website for California UC Extension