Effect of soil compaction and organic residues on spring-summer soil moisture and temperature regimes in the Sierra National Forest, California

by Troncoso, Guillermo E.

Soil moisture and temperature regimes during spring-summer 1996 were evaluated

in plots with compaction and organic residues treatments established in 1993 at three sites

in the Sierra National Forest after forest harvesting. The results indicate that the bare

condition (non-compacted soil with total removal of the harvesting residues and forest

floor), of these granitic derived soils, created a harsh environment for biological activity

due to high temperature at the top of the mineral soil (as high as 55 °C) and reduced water

availability in the first 15 cm of the mineral soil. The organic residues treatment

maintained significantly higher contents of water available. This treatment extended by

more than 1.5 months the residence time of water in the 0-15 cm of the mineral soil,

compared with the moisture levels in the bare soil condition. Maximum soil temperatures

were drastically reduced by the layer of organic residues. The compaction treatment

caused a modest increase in the moisture content, restricted to the first 30 to 40 days after

the last spring rainfall. Maximum temperatures also reached levels as high as 55 °C at the

top of the compacted mineral soil. The infiltration rate was reduced by about 50 % when

the bulk density was increased about 21 % in the 0-20 cm portion of the soil by the

compaction treatment.