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...

No abstract

Soil disturbance guidelines should be based on comparable disturbance categories adapted to specific local soil conditions, validated by monitoring and research. Guidelines, standards, and practices should be continually improved based on an adaptive management process, which is presented in this paper. Core components of this process include: reliable monitoring protocols for assessing and comparing soil disturbance for operations, certification and sustainability protocols; effective methods to predict the vulnerability of specific soils to disturbance and related mitigative measures; and, quantitative research to build a database that documents the practical consequences of soil disturbance for tree growth and soil functions.Key words: soil disturbance; soil compaction; rutting; monitoring (implementation, effectiveness, and validation); criteria and indicators; Montreal Process RÉSUMÉ Les directives portant sur les perturbations du sol devraient être établies à partir de catégories comparables de perturbation adaptées aux conditions spécifiques du sol affecté et validées au moyen d'un suivi et de recherches. Les directives, les normes et les pratiques devraient être continuellement améliorées en fonction d'un processus de gestion adaptative qui fait l'objet d'une présentation dans cet article. Les principaux éléments de ce processus comprennent : des protocoles fiables de suivi pour évaluer et comparer les perturbations au cours des opérations et pour des protocoles de certification et de durabilité; des méthodes efficaces de prédiction de la vulnérabilité de certains sols en matière de perturbation et des mesures de mitigation qui s'y rattachent; et, des recherches quantitatives pour élaborer une base de données qui documente les conséquences pratiques de la perturbation du sol sur la croissance des arbres et les fonctions du sol.

No abstract

Eight years after installation, six site preparation treatments were compared for effects on soil chemical and physical properties, nonconiferous vegetation, and the survival and growth of planted ponderosa pine (Pinusponderosa Laws.). Treatments included a logged-only control, ripping, brush blading, disking, chemical spraying (herbicide), and chemical spraying followed by disking. The brush-blade and chemical–disk treatments showed the greatest reduction in nutrient levels (total N, S, and C, and extractable P) compared with the control within the lower zone of soil sampled (15–25 cm depth). The chemical-only and disk-only treatments resulted in smaller decreases in nutrient levels, while ripping appeared to have only minor effects on soil chemical properties. Similar trends were noted in the upper soil zone (0–10 cm), although the differences were not statistically significant. Brush blading and both disking operations increased soil bulk density in the upper soil zone, but not in the lower soil zone. Aboveground biomass of shrubs was highest on the control treatment, followed by the rip, disk, brush-blade, chemical, and chemical–disk treatments. Pine survival was 78% or better for all treatments except the rip and control. The chemical–disk and chemical treatments resulted in the best height growth, followed by the disk, brush-blade, rip, and control treatments. A strong negative correlation existed between the amount of brush and pine biomass after 8 years. This study illustrates the importance of weed control to achieve maximum survival and early growth of planted pines in south central Oregon.