Friday, November 18, 2011

Brush Pile

When your management activities include actions such as brush and tree removal, there develops a need to dispose of the accumulated woody material. I’ve chosen to pile cut trees and let the material decompose on site. The piles are located in places devoid of rare plants and provide a collateral benefit as wildlife cover. In some cases I’ve tried to gain an additional benefit from the construction of the pile.

Prior to the placement of this brush pile, there was a deep actively eroding gully on the site. In certain situations, cut cedars can be used to successfully stop gully erosion. The trick is to pack the cedars so tightly together that they form a fibrous plug through which runoff water must flow. The packed cedars slow and diffuse the flow of water while filtering out organic debris. Small cedars of seven foot height or less work best, because they have a high proportion of leaves and small stems and are easily compressed. Larger cedars should also be layered into the mix to help stabilize the pack. Once that mixture reaches above the gully walls, you can build the rest of the pile any way you wish.

Properly placed cedars will cause a pool of water to form upstream of the brush pile. Vegetative debris is left behind in the pool area and begins the accumulation of organic matter in the bare area once washed clean by the running water. The improved conditions make it possible for vegetation to grow and further protect the site from erosion.

Over time, small gullies that existed above the brush pile become filled and the area takes on the shape of a broad, flat bottomed valley. This gully erosion control technique only works on gullies with small watershed areas. The cedars would never stay in place in gullies that received a large amount of runoff water.

This area is now supporting a population of Shrubby St. Johnswort, one of my favorite plants. The brush pile was put in place in February 2001, so it has taken 11 growing seasons to reach this point.

The area below the brush pile is also supporting a thick vegetative cover. This is because the velocity of the runoff water has been greatly reduced by its travel through the pile. I’m now wondering what’s going on inside the pile and what will happen as the pile decomposes further. I’ll give it another 11 years and then see how things have progressed.

No comments:

Post a Comment