ENVIRONMENTAL EFFECTS

Biomass can be obtained by harvesting small trees. Wang (1999) provides a comparison of environmental effects from a variety of systems used to harvest small trees. Systems described range from animal logging to farm equipment to cable systems. The differences in residual stand damage, cost and efficiency, and soil impacts were surveyed and described for the harvesting systems. Generally, animal logging had less impact on soil physical properties than machine logging. Disturbance to surface soil was higher from machine logging causing more nutrient losses as compared to animal logging. Machine skidding resulted in more direct damage to the residuals as compared to animal skidding. Environmental effects from specialized cable yarding and tractor-mounted tower yarding are also discussed.

Experiments have been performed to determine if mulching and incorporating the mulch into the soil would improve soil properties for pine growth. Post-harvest slash (including stumps) was mulched and incorporated into the soil (wet flats and pocosins) in a North Carolina study (Lakel and others 1999) prior to bedding. This treatment was compared to the conventional site preparation treatments for the area (v-shear and bed with a tractor-mounted plow). This study found that the differing methods of organic material incorporation did not affect soil moisture or aeration properties for the soil types in the test. In other publications, researchers tested the response of soil carbon and soil physical properties to mulched forest slash (Sanchez and others 2000 and Sanchez and others 2002a). The treatments included the conventional treatment as in Lakel and others (1999), plus strip surface mulching, strip mulching with tilling, and broadcast surface mulching. Machine costs and production rates for the Rayco Model T275 Hydra-Stumper were determined for each treatment. Potential increases in site productivity coupled with the collection of carbon sequestration credits could make the incorporation of forest slash a viable site preparation option.

A study on the Savannah River Site National Environmental Research Park (Sanchez and others 2002b) also examined various site preparation treatments involving mulch incorporation. The soil types, treatments and machines used in this study provide additional data regarding the effects of the treatments on soil chemical and physical properties. The study results indicate that incorporating forest slash during site preparation treatments has a positive effect of increasing soil carbon and nutrients. Costs and productivity information were calculated for the CMI RS 500B machine.

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