Effect of prescribed burning on soil moisture and germination of southwestern ponderosa pine seed on basaltic soils

Successful natural regeneration is dependent on many factors, including a seedbed that is suitable for germination and seedling establishment. The results of this study suggest that prescribed burning may provide such a seedbed for ponderosa pine on basaltic soils. Although overall germination was low, it was significantly higher on burned than unburned sites during a year in which precipitation was below average. Apparently, prescribed burning reduced the heavy accumulation of litter and duff, allowing seed to reach mineral soil. In contrast, vertical seed movement was minimal on unburned plots, and seeds reached mineral soil only on those plots lying beyond the canopy dripline. Furthermore, germination was probably enhanced by the generally higher moisture content in the upper 2 inches of soil on burned areas. Successful regeneration of forested areas depends on the establishment of new seedlings in sufficient numbers to adequately restock the stand. Although the study showed that burning improved germination, seedling establishment beyond the first summer was not measured. Also, the low survival rate precluded drawing any conclusions about establishment. Consequently, additional research or pilot demonstrations will be needed before the effectiveness of prescribed burning can be fully evaluated.