EFFECTS OF POCKET GOPHERS, BRACKEN FERN, AND WESTERN CONEFLOWER ON SURVIVAL AND GROWTH OF PLANTED CONIFERS

This study was part of investigations on the Grand Fir Mosaic Ecosyste m in northern Idaho that were undertaken because of poor regeneration success in harvested forests. Lack of regeneration appears to be relat ed to high populations of northern pocket gophers (Thomomys talpoides) , bracken fern (Pteridium aquilinum), and western coneflower (Rudbecki a occidentalis). This study quantified the effects of four treatments on survival and growth of planted conifers: unweeded with gophers, wee ded with gophers, unweeded without gophers, and weeded without gophers . Subalpine fir (Abies lasiocarpa), grand fir (Abies grandis), lodgepo le pine (Pinus contorta), and Engelmann spruce (Picea engelmannii) wer e planted at four study sites. After 3 years, Engelmann spruce and lod gepole pine had the lowest mortality from gophers, whereas grand fir a nd subalpine fir had the highest mortality. Most mortality caused by g ophers occurred during the first summer and the first two winters afte r planting. Lodgepole pine was the tallest of the four species after 3 years; however, lodgepole pine appears to be susceptible to snow dama ge. Englemann spruce is the recommended species for planting because o f its good growth rate (even when growing with bracken fern and conefl ower), low mortality from gophers, and its ability to withstand snowlo ads and senescing bracken fern.