The Effect of Logging and Slash-Burning on Soil Structure
1957
Dyrness, C. T. | Youngberg, C. T.
The effects of logging and slash-burning on soil structure were investigated on three Reddish Brown Latosol soils in the Coast Range of Western Oregon. Soil samples of the surface 2 inches were collected at 50-foot intervals along randomly located transects within the clear-cut areas. Soil samples were also collected in the adjacent uncut timber. The condition of the surface soil was noted at 10-foot intervals along the transects and was recorded as follows: lightly burned, severely burned, disturbed and unburned, or undisturbed. Sixty soil samples from each clear-cut sampling area were analyzed in the laboratory for mechanical composition, organic matter content, and water stable aggregates. The soil surface conditions after logging and slash-burning were as follows: lightly burned 44.7%, severely burned 8%, unburned 30.1%, and undisturbed 17.2%. Severe burning was the only treatment that had any significant effects upon soil structure, particle size distribution and soil organic matter content. Analysis of variance revealed that there was a significant decrease in the amount of clay present in the severely burned soils as compared with the soils under undisturbed timber. A 20.6% decrease in the degree of aggregation and a 61.1% decrease in organic matter content were also noted in the severely burned soils as compared with soils in the undisturbed timber. Other treatments had no significant effects upon the soils of the logged area. Since only 8% of the soil surface was severely burned, it is concluded that logging by the high lead method and slash-burning in the fall after rainfall has occurred have had no appreciable detrimental effects upon soil structure in the area studied.
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