331 research outputs found
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Detection of dwarf mistletoe in young-growth ponderosa pine from color aerial photography
The purpose of this study was to determine if infection levels of dwarf mistletoe on ponderosa pine could be detected with color aerial photography. The photography was taken in early September using Kodak Ektachrome Infrared Aero and Ektachrome Aero films at scales of 1/4000, 1/2000, and 1/1000. Ground truth consisted of 214 trees classified as to healthy, lightly infected, moderately infected or heavily infected. Three photo interpreters were able to correctly classify these trees only 34 percent of the time. Statistical analysis indicated no significant differences between interpreters, film types, scales, or levels of infection. Rearrangement of the data did indicate that four interpreters were able to distinguish mistletoed from non-mistletoed trees 70 percent of the time using Ektachrome Infrared Aero film at a 1/1000 scale. Results might be improved by using low oblique photography taken in the spring with either Kodak Ektachrome aero or Ektachrome Infrared Aero films, at a scale of 1/1000
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Evaluation of individual-tree and disaggregative prediction methods for Douglas-fir stands in western Oregon
The efficiency of six disaggregative methods and two individual-tree methods was evaluated in terms of their ability to predict 5-year basal area increment for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in western Oregon. Models were developed for predicting gross stand basal-area increment and individual-tree diameter increment. In addition, models were developed to disaggregate the active increment prediction methods to the tree level. Passive and active prediction schemes were evaluated for both the tree and stand levels. Generally, the individual-tree approach was superior to the disaggregative approach for prediction of both stand and tree growth. This was less evident, however, when crown ratio was eliminated from the individual-tree models. This suggests that at least some of the disparity between the two is due to the presence of crown ratio in an individual-tree passive aggregation approach. The additive disaggregation approach appeared to be best suited to young stands (less than 50 years of age). The linearity assumption required for this particular model appeared to be violated for older stands with larger trees. Generally, the two whole-stand, gross-growth models used in this study were inferior to the individual-tree method for predicting gross basal area growth for one period.Keywords: individual-tree prediction methods, basal-area increment, disaggregative prediction methods, tree growth, stand growth, crown ratio, Douglas-fir (Pseudotsuga menziesii)Keywords: individual-tree prediction methods, basal-area increment, disaggregative prediction methods, tree growth, stand growth, crown ratio, Douglas-fir (Pseudotsuga menziesii
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Height-diameter equations for sixteen tree species in the central western Willamette Valley of Oregon
Equations for predicting tree height as a function of diameter
outside bark at breast height are presented for 16 tree species
from the central western Willamette Valley of Oregon. Foresters
can use these "height-diameter" equations to avoid the time consuming
task of measuring heights of all individual trees in an
inventory, a stand exam, or a timber cruise. Equation coefficients
were estimated with weighted nonlinear regression techniques.
Because site index can influence height, alternative equations including
transformations of site index as an independent variable
also are presented for 6 of these 16 species
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Height-diameter equations for six species in the coastal regions of the Pacific Northwest
Three equations for predicting tree height as a function of diameter (outside
bark) at breast height are presented for six species found in coastal regions of
the Pacific Northwest. Foresters can use these “height–diameter” equations
to avoid the time-consuming task of measuring heights of all individual trees
in an inventory, a stand exam, or a timber cruise. Equation coefficients were
estimated with weighted nonlinear regression techniques. Because the relationship
between a tree’s height and diameter depends on the tree’s competitive
position within the stand, alternative equations, including the average
height and average diameter of the 40 largest-diameter trees/ac, are also
presented. These equations are used in the Stand Management Cooperative
version of ORGANON
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Predicting height for undamaged and damaged trees in southwest Oregon
Equations for predicting tree height as a function of diameter outside bark at
breast height are presented for various tree species common to southwest
Oregon. Data for damaged and undamaged trees were analyzed with weighted
nonlinear regression techniques. The effects of specific damaging agents and
their severity on the height-diameter relationship were explored. Damage correction
multipliers were estimated, then used to correct predicted height where
damage was noted. Because the relationship between height and diameter
changes with the competitive position of the tree in a stand, alternative equations
are presented that include the average height and diameter of the 40
largest-diameter undamaged conifer trees per acre. Foresters can use these
“height-diameter” equations to reduce the time-consuming task of measuring
heights of every tree in an inventory, stand exam, or timber cruise. They
can also use these equations to estimate the change in height as diameter
changes. These equations will be incorporated into the new southwest Oregon
version of ORGANON, which extends the model to older stands and
stands with a heavier component of hardwood species
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Evaluation of mixed-effects models for predicting Douglas-fir mortality
We examined the performance of several generalized linear fixed- and mixed-effects individual-tree mortality models for Douglas-fir stands in the Pacific Northwest. The mixed-effects models accounted for sampling and study design overdispersion. Inclusion of a random intercept term reduced model bias by 88% relative to the fixed-effects model; however, model discrimination did not substantially differ. An uninformed version of the mixed model that used only its fixed effects parameters produced predicted mortality values that exceeded the fixed-effects model bias by 31%. Overall, we did not find compelling evidence to suggest that the mixed models fit our data better than the fixed-effects model. In particular, the mixed models produced fixed-effects parameter estimates that predicted unreasonably high mortality rates for trees approaching 1 m in diameter at breast height.Keywords: Douglas-fir, Mortality, Generalized linear model, Mixed mode
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A key to the literature presenting tree volume and taper equations for species in the Pacific Northwest and California
Summaries from 49 published articles on tree volume and taper equations are presented for 39 tree species found in California, Oregon, Washington, British Columbia, southeast Alaska, Idaho, and western Montana. The summaries are organized by species and then by type of equation (volume or taper). Each summary describes the types of dependent variables predicted by the equations and the geographic location, number of trees, range in DBH, and range in total height for trees in the sample used to develop the equations
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Equations for predicting the largest crown width of stand-grown trees in western Oregon
Largest crown width (LCW) equations for stand-grown trees were developed for 14 tree species found in western Oregon. The equations are used in the growth-and-yield model ORGANON and in the stand-visualization program VIZ4ST. They were constructed such that LCW equals the maximum crown width
of open-grown trees when the crown ratio is equal to one. Tree measurements needed for the equations are diameter at breast
height (in.), total tree height (ft), and crown length (ft)
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Extending southwest Oregon's Douglas-fir dominant height growth equation to older ages
Hann and Scrivani (1987) developed dominant height growth equations for Douglas- fir in southwest Oregon using stem analysis data sets with an upper age of approximately 125 years at breast height. The objective of this study was to determine whether these equations could be extrapolated for ages of 250 years or more. Data for the evaluation came from stem analysis of 60 dominant trees located in 30 "older" stands. Intensive data screening indicated that 53 of these trees exhibited signs of reduced height growth during their first 100 years of development due to competition from non-tree vegetation, hardwood tree species, and possibly other conifers in non-even-aged stands. Analysis of the remaining seven site-quality trees indicated that the existing dominant height growth equation for Douglas-fir could be extrapolated to breast height ages of up to 245 years without loss of accuracy or precision
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A key to the literature presenting site-index and dominant-height-growth curves and equations for species in the Pacific Northwest and California
Summaries from 49 published articles on site-index and dominant-height growth curves and equations are presented for 20 tree species or species groups found in California, Oregon, Washington, British Columbia, southeastern Alaska, Idaho, and western Montana. The summaries are organized by species. Each summary describes the modeling approach, type of curves/equations, base age, and type of age presented in the article. In addition, the geographic location, number of trees or plots, range in age, and range in site index used to develop the curves/equations are also described
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