Abstract:We (i) quantified effects of skidder yarding on soil properties and seedling growth in a portion of western Oregon, (ii) determined if tilling skid trails improved tree growth, and (iii) compared results with those from an earlier investigation in coastal Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were hand planted at eight recent clearcuts in skid ruts in either nontilled or tilled trails, in adjacent soil berms, and in adjacent logged-only portions. Four and 5 years after skidding, rut depths averaged 15 cm below the original soil surface; mean fine-soil bulk density (0-30 cm depth) below ruts of nontilled trails exceeded that on logged-only portions by 14%. Height growth on nontilled trails averaged 24% less than on logged-only portions in year 4 after planting and decreased to 6% less in year 7. For years 8-10, mean height growth was similar for all treatments. Reduced height growth lasted for about 7 years compared with 2 years for coastal Washington. Ten years after planting, trees in skid-trail ruts averaged 10% shorter with 29% less volume than those on logged-only portions. Tillage improved height and volume growth to equal that on logged-only portions. Generalizations about negative effects of skid trails on tree growth have limited geographic scope. R~sum~ : Nous avons (i) mesur6 les effets du d6bardage par t616ph6rage sur les propri6t6s du sol et la croissance de jeunes arbres dans une partie de l'ouest de l'Oregon, (ii) d6termin6 si le fait de labourer 16g~rement le sol dans les ornitres am~liore la croissance des arbres et (iii) compar6 nos r6sultats avec une exp6rience prdc6dente r6alis6e dans la r6gion c6ti6re de l'6tat de Washington. Des semis de douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) ont 6t6 plant6s manuellement sur le site de huit coupes ~ blanc r6centes, dans des ornibres labour6es ou non, dans les talus adjacents et dans des coupes adjacentes. Quatre et 5 ans apr~s le d6bardage, la profondeur des orni~res atteignait en moyenne 15 cm sous la surface initiale du sol; la densit6 moyenne du sol (0 ~t 30 cm de profondeur) sous les orni~res non labour6es 6tait 14% plus 61ev6e que celle des zones qui avaient seulement 6t6 coup6es. La croissance en hauteur des arbres dans les orni~res non labour6es 6tait, en moyenne, inf6rieure de 24% ~t celle observ6e dans les zones qui avaient seulement 6t6 coup6es 4 ans apr~s la plantation et la diff6rence n'6tait plus que de 6% inf6rieur apr~s 7 ans. Entre la huiti~me et la dixibme ann6e, la croissance moyenne en hauteur des arbres 6tait similaire pour tousles traitements. La rdduction de croissance a dur6 environ 7 ans comparativement ~t seulement 2 ans dans la r6gion c6tibre de l'6tat de Washington. Dix ans apr~s la plantation, les arbres qui avaient pouss6 dans les ornibres 6taient 10% plus petits et avaient un volume inf6rieur de 29% aux arbres dans les zones qui avaient seulement 6t6 coup6es. Le labourage a amdlior6 la croissance en hauteur et en volume des arbres au point d'6galer celle dans les zon...
Application. Stratification of red alder seeds is recommended to improve the speed and possibly completeness of germination if temperatures are expected to be less than optimum such as in the case of most outdoor nursery beds in the Pacific Northwest of the United States in early spring . In the case of seedling production in greenhouses, we suggest that temperatures be regulated to achieve optimum germination results .Abstract . Two-to four-week stratification of red alder seeds slightly increased the speed of germination but did not improve total germination under alternating warm temperatures (30 °C/20 °C), yet significantly improved speed and total germination under cool temperatures (15 °C/5 °C) that simulated early spring outdoor nursery bed conditions . Only seeds that received four-week stratification achieved complete germination at the cooler temperatures. Strong seed source variation in response to seed treatments was observed at the cool regime. The Yacolt source germinated well regardless of seed treatments, even without stratification, while five other sources needed two to four weeks of stratification to achieve above 50% germination . Possible reasons for this variation are discussed .
Diameter and height growth of 7- to 11-yr-old Douglas-fir (Pseudotsuga menziesii) were examined in relation to bigleaf maple (Acer macrophyllum) competition. Growth models were developed for plantations in Oregon and Washington by joining a distance-dependent model with a model that excluded competition effects. The fitted equations were based on Douglas-fir size at plantation age 7 yr and distance from the stump and crown diameter of the bigleaf maple clump. The models suggest that bigleaf maple clumps between 5.7-14.6 m from planted Douglas-firs decrease the latter's dbh and height growth, and that this decrease becomes greater with increasing size of the clump. A procedure is suggested to use the models to guide vegetation management prescriptions on sites with bigleaf maple sprout clumps. West. J. Appl. For. 10(1):5-11.
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