1. Response of coastal Douglas-fir and competing vegetation to repeated and delayed weed control treatments during early plantation development
- Author
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Maguire, Douglas A., Mainwaring, Douglas B., Rose, Robin, Garber, Sean M., and Dinger, Eric J.
- Subjects
Forest dynamics -- Research ,Weeds -- Control ,Douglas fir -- Research ,Earth sciences ,Research ,Methods - Abstract
A key silvicultural decision in managing young conifer plantations is determining the number and timing of release treatments to control competing vegetation. Three coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantations were treated under eight alternative herbicide regimes during the first 5 years after planting to test treatment effects on vegetation dynamics and seedling growth. After termination of herbicide treatments, competing vegetation developed at a rate similar to that of check plots, reaching 40%-60% cover in the first growing season and approaching 100% by the third. Recovery of competing vegetation was slightly more rapid with greater number of previous releases. Annual volume growth of seedlings was negatively correlated with current cover of competing vegetation, but competitive effects from previous years were fully accounted for by initial tree size. Under 4 years of release, delaying treatment by 1 year reduced volume attained at the end of 5 years by about 15%. Plots receiving 5 consecutive years of weed control reached the 5 year volume of check plots in only 3.9 years, implying an age shift of 1.1 years. Increasing the number of operational release treatments significantly improved seedling growth in the short term, but long-term growth effects must be monitored to determine the economically optimal regime. Determiner le nombre et le moment d'application des degagements pour maitriser la vegetation competitrice constitue une decision sylvicole cruciale pour l'amenagement de jeunes plantations de coniferes. Trois plantations cotieres de douglas de Menues (Pseudotsuga menziesii (Mirb.) Franco) ont ete traitees a (aide de huit regimes d'herbicide differents pendant les cinq premieres annees apres la plantation de facon a tester les effets des traitements sur la dynamique de la vegetation et la croissance des semis. Apres (application des traitements d'herbicide, la vegetation competitrice s'est developpee a un rythme similaire a celui des temoins, ce quia permis a son couvert d'atteindre de 40 % a 60 % pendant la premiere saison de croissance et d'approcher 100 % lors de la troisieme saison de croissance. La recuperation de la vegetation competitrice a ete legerement plus rapide dans le cas des traitements comportant un grand nombre de degagements anterieurs. La croissance annuelle en volume des semis etait negativement correlee au couvert de vegetation competitrice observe la meme annee, mais les effets de la competition des annees anterieures etaient pleinement expliques par la taille initiale des semis. Pour le traitement comportant quatre degagements annuels, le fait de retarder le traitement d'une annee a reduit d'environ 15 % le volume atteint a la fin d'une periode de 5 ans. Les parcelles ayant recu cinq degagements annuels consecutifs ont atteint le volume quinquennal des temoins en seulement 3,9 ans, ce qui correspond a une reduction du temps requis de 1,1 an. L'augmentation du nombre de traitements de degagement a significativement ameliore la croissance des semis a court terme, mais on doit suivre les effets a long terme sur la croissance des semis pour determiner le regime optimal du point de vue economique. [Traduit par la Redaction], Introduction Control of competing vegetation is often important for successful plantation establishment and can significantly increase early tree growth in many forest types (Cole and Newton 1987; Newton and Preest [...]
- Published
- 2009