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Restoration of ingrown stands of ponderosa pine (Pinus ponderosa) and interior Douglas-fir (Pseudotsuga menziesii var. glauca) was carried out using a prescription of partial cutting and slashing in 1999 and 2000. Partial cutting consisted of thinning the forest canopy and removing intermediate layer trees. Slashing consisted of cutting pre-commercial, intermediate layers to reduce the risk of crown fire during prescribed understory burns. The ponderosa pine stand was subjected to a prescribed fire in April 2004. The partial-cut treatment opened the canopy by 30% at the ponderosa pine site. Three years later, pinegrass production had recovered at a greater rate than most bunchgrasses. Bunchgrass composition had declined in the plant community relative to pinegrass (Calamagrostis rubescens). Total forage standing crop had not yet increased beyond pre-treatment levels. The partial-cut treatment opened the canopy by 27% at the interior Douglas-fir site. Five years later, pinegrass production doubled while bunchgrass remained unchanged. Total forage standing crop increased by about 40%, almost all due to pinegrass increase. A key objective of dry-forest restoration is to increase the abundance of important forage species such as bluebunch wheatgrass (Pseudoroegneria spicata) and rough fescue (Festuca campestris), while reducing the abundance of their primary competitor, pinegrass. It is clear that this objective has not yet been achieved at these two sites. It may require more than 10 years to realize a shift toward greater composition of late-seral bunchgrass species. Selection of sites for restoration should be based on the greatest existing composition of bunchgrass if increases of bunchgrass are required in the short term. The prescribed fire applied at the ponderosa pine site in 2004 resulted in a depression of forage standing crop and canopy cover for most of the important plant species after one growing season. It is expected that forage standing crop and canopy cover response to the prescribed fire will peak over the next two years. A second key objective of dry-forest restoration is to increase the abundance of important browse species for wildlife (e.g., saskatoon [Amelanchier alnifolia] and antelope-brush [Purshia tridentata]). Interim results of this study show that these shrubs have not benefited from the initial restoration treatment of partial cutting (~30% canopy removal). So far, all shrub species at both sites have lower canopy cover than before the partial-cut was applied. Prescribed fire at the ponderosa pine site reduced the cover of saskatoon and antelope-brush even further.
Reg Newman.
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