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Our Research

Wood Stack Preservation

The Problem

Fuels reduction programs involve mechanical or hand thinning projects, removing trees to reduce forest density and to improve forest health. While larger logs are removed for use, slash piles are built from limbs, leaves, pine needles and miscellaneous fuel left by natural debris. Slash piles are created by gathering these materials into manageable, isolated piles, usually less than six feet wide and under five feet high. Typically, these piles are allowed to dry for at least six months and then burned. The resulting smoke can result in unhealthy or hazardous air quality. Burning also accelerates the return to the atmosphere of carbon dioxide, contributing to climate change.


Slash pile in Kaibab National Forest, Arizona


Emissions from burning slash pile

Our Solution

As an alternative to burning, Yale's Carbon Containment Lab designed an experiment to determine the rate of decomposition of wood in slash piles as it relates to stack foundation, stack design, and cover type. Specifically, is there a combination of stack form (foundation/design) and cover that slows decay to below 3% over 10 years?  Most carbon is lost during first 10 years of decay.


We build stacks either directly on the ground or on top of an impermeable tarp (stack foundation).  They were either covered with an impermeable tarp or left exposed (cover type).  Stacks were built either on a raft foundation or on a foundation of randomly placed logs.                                                                 



Uncovered stack built with raft foundation on impermeable tarp


Covered stack built with raft foundation on impermeable tarp



Covered stack built with random foundation on ground


Uncovered stack built with random foundation on ground


To measure the amount of decomposition over time, three “cookies” were placed in each of the 24 stacks.  These cookies, 10 to 15mm in diameter, roughly 10mm long sections of Monterey Pine, were enclosed in a wire mesh cages and placed just above the lowest log in the stack.

The Impact

One cookie from each of the stacks will be removed after two years and analyzed by Yale's Carbon Containment Lab to determine its percentage of carbon.  This value will be compared to the value measured from a similar cookie from the same log.  This procedure will be repeated at the end of year four and at the end of year six.  This will allow us to calculate the rate of decomposition as a function of ground cover, stack cover, and stack foundation.


Full view of experiment

Site video after two years

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