336 research outputs found
Role of Competition in Restoring Resource Poor Arid Systems Dominated by Invasive Grasses
An understanding of competition intensity and importance may be a useful step in helping managers understands how to prioritize restoration efforts in resource poor environments within the semi-arid steppe. The aims of this study were to quantify the intensity of competition among invasive annual grasses and native perennial bunchgrasses, and determine the importance of competition in explaining variation in target plant biomass and survivorship in a Wyoming big sagebrush steppe community type in southeastern Oregon, USA. Addition series experiments were conducted in 2008 and 2009 among four species. Treatments consisted of monoculture densities of each species to assess intraspecific competition, and mixtures of two, three and four species (interspecific competition), producing varying total densities and species proportions. We found no evidence that intensity of intra- or inter-specific competition were significant for the first two years species were establishing, regardless of the density used as the independent variable. Our results indicate that neither the intensity of competition nor the importance of competition explained variation in target plant biomass and survivorship for the first two years plants were establishing. Instead abiotic factors may have an overriding influence on plant biomass and survivorship.We propose four scenarios which may apply to semi-arid environments during the initial phase of restoration
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Influence of red alder competition on cambial phenology and latewood formation in Douglas-fir
To better understand the influence of competition on wood formation and wood quality in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), patterns of cambial growth and latewood production were examined for one growing season in 15-year-old plantations with similar densities but differing Douglas-fir/red alder (Alnus rubra Bong.) ratios. The treatments consisted of plots having different proportions of Douglas-fir vs. red alder,
different red alder planting dates, and one of two total planting densities. Cambial growth was tracked using the pinning method. Cambial activity in most trees began between May 12 and May 23, and ended between August 27 and September 10. Mean date of transition to latewood was July 6. In the treatment with the highest mean red alder basal area, Douglas-fir trees began radial growth later and ended earlier in the year than those in pure Douglas-fir stands. There was no evident effect of competition
from red alder on the duration of cambial activity in treatments with intermediate to low red alder basal areas. In all treatments, the duration of radial growth was shorter in smaller-diameter trees. Early transition to latewood production was also associated with higher red alder basal area. Percent latewood was unaffected by treatment, but it was dependent on the date of a treeÊŒs transition to latewood production.Keywords: latewood, cambial growth, red alder, Douglas-fir, phenolog
Does the resistance to glyphosate herbicide affect the competitive ability of ryegrass with soybean?
Improving Diabetes Care in Practice: Findings from the TRANSLATE trial
OBJECTIVEâThe purpose of this study was to determine whether implementation of a multicomponent organizational intervention can produce significant change in diabetes care and outcomes in community primary care practices
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