Fall Planting and Tree Shelters for Reforestation in the East Washington Cascades

摘要

Reforestation on harsh, high-elevation sites near the crest of the Cascade Mountains in Washington can be challenging because of persistent snowpack and extreme climatic variation. The use of free shelters was investigated with two species, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and western larch (Larix occidentalis Nun.), on two Yakama Notion sites across three fall planting dates. For both species, seedlings inside free shelters had increased survival compared with nonsheltered seedlings after one growing season despite increased damage by crushing from snowpack. Volumetric soil moisture content on the western larch site increased from 10% to 17% between the first and second planting dates, resulting in no effect of planting date on western larch survival. On the Douglas-fir site, however, soil moisture content was below 12% for all fall planting dates, resulting in only 2% survival for those seedlings planted on the first planting date. First-season seedling growth was unaffected by planting date or tree shelter treatment for both species. These results indicate the critical importance of soil moisture at time of planting and onset of precipitation after planting. Use of tree shelters may improve seedling survival on a harsh, high-elevation site, but it increases potential seedling damage because of crushing by snowpack.