UC Davis Department of Plant Sciences

RIPARIAN ECOSYSTEM RESPONSE TO TIMBER HARVSESTING FOR THE PURPOSE OF RESTORING ASPEN


Soil Moisture

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The statistical analysis results show that treatment soil moisture at both depths increased significantly relative to reference soil moisture in response to Phases 2 and 3 of the Pine-Bogard Project and in response to the Bailey Project (P < 0.001).

The greater retention of soil moisture within treatment transects is likely the result of the removal of vegetation causing a reduction in evapotranspiration, which sustains high soil moisture levels into the dry season. These high soil moisture levels have the potential to be maintained if the site is successfully recolonized by aspen, because mature conifer forests use more water than mature aspen forests.

Fig. 11 reports the average soil moisture tension (higher soil moisture tension indicates drier soils) made at the reference and treatment transects at the 6 in depth (% P = percent annual precipitation). Results at 18 in depth are the same as reported for the 6 in depth and thus are not displayed.

The figure shows that treatment transects exhibited a lower rate of drying relative to reference transects following both Phase 2 and Phase 3 conifer removal, thereby increasing the difference (Δ) between reference and treatment transect soil moisture.

Fig. 11 also shows that at Bailey Creek, average soil moisture was lower in the treatment transects than in the reference transects before treatment. Following conifer removal however, soil moisture was higher in the treatment transects than in the reference transects.

 

 

       

 

 

 

Figure 11. Mean and standard error of soil moisture measured at the 6 inch depths of the reference and treatment transects located within the Pine-Bogard Phase 2, Pine-Bogard Phase 3, and Bailey project areas.

 

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