Comparison of 5th - and 14th - year Douglas - fir and understory vegetation responses to selective vegetation removal
The effects of early vegetation management on the survival and growth of Douglas-fir [. Pseudotsuga menziesii [Mirb.] Franco] were examined 5 and 15. years after planting in the Oregon Coast Range. Our first objective was to document the effects of vegetation species competition upon key ecosystem p...
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| Otros Autores: | , , , , |
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| Formato: | Artículo |
| Lenguaje: | Inglés |
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| Acceso en línea: | http://ri.agro.uba.ar/files/intranet/articulo/2011Yildiz.pdf LINK AL EDITOR |
| Aporte de: | Registro referencial: Solicitar el recurso aquí |
| Sumario: | The effects of early vegetation management on the survival and growth of Douglas-fir [. Pseudotsuga menziesii [Mirb.] Franco] were examined 5 and 15. years after planting in the Oregon Coast Range. Our first objective was to document the effects of vegetation species competition upon key ecosystem properties. The second objective was to document the effects of vegetation removal during early Douglas-fir stand establishment upon long-term tree growth and on biomass production by vegetation components. Seven levels of manual vegetation removal were maintained for the first 5. years after planting: 0 percent, 25 percent, 50 percent, 75 percent, and 100 percent shrub removal; and 100 percent shrub removal combined with 50 percent or 100 percent herbaceous vegetation removal. Shrub and herb removal did not affect Douglas-fir survival at year five, but treatments providing less than 75 percent shrub removal significantly reduced Douglas-fir survival by year 15. Removing shrubs and herbs completely [100S. +. 100H] during the 5. years following tree planting allowed successful tree establishment, with a 366 percent increase in biomass accumulation per hectare for Douglas-fir in that treatment at the end of 14. years of growth. At 15. years stand age, even with shrub removal alone, a 304 percent gain in tree biomass per hectare was obtained compared to no vegetation removal [NVR]. By stand age 15. years, any increase in the degree of understory removal beyond 75 percent did not contribute significantly to additional tree survival and growth. The understory vegetation on NVR treatment plots and the herbaceous vegetation on 100 percent shrub removal [100S] treatment plots, contained more than 90 percent and more than 80 percent of aboveground biomass N at 5. years, respectively, indicating possible competition for soil N. Soil moisture was not different among treatments at 5. years. Complete vegetation removal [100S. +. 100H] for 5. years resulted in a significant increase in soil bulk density [P less than 0.05], a significant decrease in total soil C [P less than 0.05] and no change in total soil N in the upper 15. cm of the mineral soil. By 14. years, however, only the soil bulk density remained greater [P less than 0.05] on the 100S. +. 100H treatment. We conclude that greater tree survival and growth occurred with at least 75 percent shrub removal. Our results suggest that managers may have substantial flexibility in maintaining a partial understory component suitable for ecosystem productivity, canopy cover and wildlife habitat, while maintaining forests productive for timber resources. |
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| ISSN: | 0378-1127 |