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A stand-level modeling system for young Douglas-fir plantations applicable to the Coast Ranges of the Pacific Northwest was developed by using data from 84 growth-monitoring plots. Specific components of the system for predicting current size distributions of planted Douglas-fir include: dominant height and survival of planted Douglas-fir; a basal area projection equation for hardwoods; and diameter distribution percentile prediction functions for planted Douglas-fir. Prediction equations for height, crown width, and height to crown base of individual trees describe stand structure of the planted Douglas-fir. The stand- and tree-level equations include both direct and indirect effects of hardwood competition and site preparation, competition release, and precommercial thinning treatments. With the exception of minimum dbh, stand-level equations for planted Douglas-fir explained at least 92% of the observed variation. Basal area dynamics were simulated through plantation age 20 years for site preparation and competition release treatments of different effectiveness by varying hardwood basal area at plantation age 5 years. The simulations indicate that site preparation must reduce hardwood basal area at plantation age 5 years by 75% or more to realize an increase in Douglas-fir basal area and shift of the diameter distribution toward larger trees. This is due to increased growth of hardwoods that survive site preparation. In contrast, competition release treatments exhibited positive Douglas-fir response with 50% efficacy or more. Therefore, ineffective site preparation treatments need to be followed with competition release treatments having at least 50% efficacy to produce similar Douglas-fir basal area and diameter distributions at age 20 as in stands with no site preparation. West. J. Appl. For. 20(2):77–93.

Data from an eastern cottonwood clonal mixing study in Mississippi and Kentucky, USA, were used to test the effects of planting locations and genetics (clonal proportions) on height–age and height–dbh functions. Planting locations, which accounted for 5.6% of the variation in observed dominant height growth ( p =0.0001), were more important than clonal proportions, which accounted for only 1.0% of the variation ( p =0.0077). Interactions between clones in mixtures were not significant ( p =0.9178), but three cases of over- and undercompensation paralleled those observed for basal area. Planting locations were associated with differences in maximum height in the height–dbh function and clonal proportions were associated with differences in height of trees with smaller than average dbh. Although statistically significant, the effects of planting locations and clonal proportions were not important enough to incorporate into the final height–dbh model.

Four equations were developed for predicting the probability of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) survival for the first (0–1) and first to third (1–3) growing seasons after applying mulching, scalping, or artificial shading (shade cards) treatments in plantations in southwestern Oregon, U.S.A. Variables describing conifer size, levels of competing vegetation, presence of silvicultural treatments, site factors, and climate factors were collected from 13 sites ranging from 0 to 6 years after planting and examined as potential predictors of survival. Age, stem diameter, a competition index for shrubs, severity of growing season at time of treatment, average annual precipitation, aspect, and slope angle were predictors of Douglas-fir survival during 0–1 and 1–3 growing seasons after treatment; the presence of silvicultural treatments was also a predictor only during the first growing season after treatment. Age, aspect, and slope angle were predictors of ponderosa pine survival over both 0–1 and 1–3 growing seasons after treatment; height-diameter ratio, competition indices for herbs, shrubs, and hardwoods, silvicultural treatment, severity of growing season at time of treatment, and average annual precipitation were also predictors only during the first growing season after treatment; crown width was a predictor of survival only during 1–3 growing seasons after treatment. When significant in the models, predicted probability of survival increases with treatments, less severe weather conditions, diameter, crown width, age, and precipitation; probability decreases with increasing height-diameter ratio and competition indices for herbs, shrubs, and hardwoods.

A red alder planting spacing study was used to compare three modeling approaches that have been successfully used for other tree species. These three approaches predict stand structure and dynamics in plantations that are 7 to 16 years old, with planting densities of 976 to 13 899 trees/ha. The diameter-distribution-prediction approach tended to over-predict the diameter at breast height (dbh) for larger trees in stands planted at low density and to under-predict dbh for smaller trees in stands planted at high density. This approach may be useful for comparing planting densities when a tree list is not available. The stand-table-projection approach tended to under-predict dbh for smaller trees in young stands planted at low density and to over-predict dbh for smaller trees in young stands planted at high density. This approach, however, provided consistency between stand- and tree-level growth projections, and should be useful for comparing planting densities when a tree list is available. The individual-tree-growth approach provided the best representations of observed diameter distributions at all planting densities, stand ages, and growth intervals. This approach may be best suited for stands that have been thinned, stands with mixtures of species, and stands with heterogeneous size classes.

The response of stand structure and dynamics of young red alder ( Alnus rubra Bong.) was examined over a gradient in planting density. Data from three Nelder plots, representing ages 1–7 years and planting densities from 238 to 101 218 trees ha −1 , were used to develop biomathematical models for dominant height, diameter, and survival. The models accounted for 88–99% of the observed variation in projected height, diameter, and survival, with planting density accounting for 0.6–2.6% of the variation in diameter and height and 7.1% of the variation in survival. Height growth rate exhibited a quadratic relationship with planting density up to 24 670 trees ha −1 and a linear relationship at greater planting densities. The natural logarithm of planting density exhibited a linear relationship with change in relative diameter and quadratic mean diameter growth rates. These functional relationships between growth rates and planting density were consistent with the concepts of competition thresholds: height and diameter growth rates were more affected by planting density at lower than at higher planting density while mortality rate increased linearly with increasing density. At high planting density, annual height and quadratic mean diameter growth were less and reached a maximum at younger ages than at low planting density. The dominant height projection function depicts a temporal ripple in maximum height growth that progresses outward over time from the high planting densities in the center of Nelder plots to the lower densities near the edge of the plots.

Quadratic response functions were demonstrated for predicting crown reduction of red alder (Alnus rubra) and vine maple (Acer circinatum) after application of the herbicides glyphosate and triclopyr in combinations with imazapyr. Relationships between crown reduction and the application dates and rates were explored with data from five experiments previously conducted in Oregon in order to estimate optimal timing and optimal rates for each herbicide. The best crown reduction with glyphosate-imazapyr was achieved in the Cascade Mountain foothills with June or July applications and in the Coast Range with August or September applications. Control of red alder was best with 0.05 to 0.09 lb (ae/ac) imazapyr; the additive effect of glyphosate rate was more important in July than in August applications. The optimum imazapyr rates for vine maple may be outside the range of rates included in the studies, and rainfall shortly after the July application compromised the results for one study. Compared to crown reduction of vine maple with the individual herbicides, the effect with glyphosate-imazapyr varied from none to slightly positive, and that with triclopyr-imazapyr from slightly negative to additive. The response model accounted for 69-88% of the observed variation in crown reduction of vine maple. The model for red alder accounted for 44% of the variation in crown reduction. West. J. Appl. For. 10(4):127-132.

Diameter prediction models based on the Weibull distribution function and stand-table projection models based on changes in relative diameter were developed for 2- to 10-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations. Both modeling approaches incorporated the effects of site preparation, animal protection, and competing vegetation. The diameter distribution approach is appropriate when information on initial diameters is not available. The stand-table projection approach may be applied when tree diameters in a plantation are measured two or more growing seasons after planting. At young ages, the stand-table approach provided more accurate representation of observed diameter distributions than the diameter distribution approach. At age 10 the two methods provided comparable diameter distributions. The equations derived for predicting survival, height growth of dominant trees, height–diameter relationships, and the development of woody vegetation over time will facilitate the study and comparison of stand structure and dynamics after various site-preparation and animal-protection treatments.

An evaluation of six objective estimators of treatment efficacy for bigleaf maple (Acermacrophyllum Pursh) was made on the basis of data from two herbicide screening studies. The estimators were evaluated for sensitivity to statistical comparison of treatment means. Evaluation was made on the basis of (i) overall mean and coefficient of variation for percent change in crown volume, as well as (ii) percent control based on regression-adjusted post-treatment crown height, (iii) crown diameter, (iv) crown profile, (v) crown area, and (vi) crown volume. Estimates of overall mean control were similar among the expressions of crown size, but the estimate based on change in crown volume was substantially lower. The coefficient of variation was smallest when control was calculated from crown height or crown profile and was largest for change in crown volume. Orthogonal contrasts indicated that control calculated from one- and two-dimensional expressions of crown size tended to be more sensitive to treatment differences than other expressions of crown size. Change in crown volume and control calculated from crown volume tended to be the least sensitive to treatment differences, resulting in rejection of the null hypothesis for fewer orthogonal contrasts. These results for bigleaf maple are consistent with the results obtained for several hardwood species in the southeastern United States.

Diameter and height growth of 7- to 11-yr-old Douglas-fir (Pseudotsuga menziesii) were examined in relation to bigleaf maple (Acer macrophyllum) competition. Growth models were developed for plantations in Oregon and Washington by joining a distance-dependent model with a model that excluded competition effects. The fitted equations were based on Douglas-fir size at plantation age 7 yr and distance from the stump and crown diameter of the bigleaf maple clump. The models suggest that bigleaf maple clumps between 5.7-14.6 m from planted Douglas-firs decrease the latter's dbh and height growth, and that this decrease becomes greater with increasing size of the clump. A procedure is suggested to use the models to guide vegetation management prescriptions on sites with bigleaf maple sprout clumps. West. J. Appl. For. 10(1):5-11.

Height-age and height-diameter models for plantations of young Douglas-fir ( Pseudotsuga menziesii [Mirb.] Franco var. menziesii ) were examined in relation to vegetation management treatments. The models were developed from 10 years of measurements in a competition release study installed on six sites in the Coast Ranges of Oregon and Washington. Analysis of height growth patterns for dominant trees indicated significant differences between the total vegetation control treatment and operational release treatments or no treatment. The resulting height-age function depicted exponential growth patterns for the total vegetation control treatment and nearly linear patterns for the operational release treatment and no treatment. The height-diameter function was compatible with dominant height growth and quadratic mean diameter prediction functions. Different height-diameter curve shapes were associated with total vegetation control and the operational release and no treatments. The resulting function implied that Douglas-fir trees of a given diameter and age were slightly taller when under interspecific competition, especially for trees with smaller diameters. The height-age and height-diameter functions may be used in conjunction with diameter distribution or stand table projection models developed for those data to predict dynamics and stand structure in young Douglas-fir plantations.

A stand table projection system based on individual-tree and stand-level models for young Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) plantations was developed from and evaluated with remeasurement data from sites in the Siskiyou Mountains of southwestern Oregon and in the Coast Ranges of Oregon and Washington. A projection equation was developed for relative tree size, defined as the ratio of individual-tree diameter at 15 or 30 cm above ground level (depending on the study location) to quadratic mean diameter. The relative size projection equation for the Coast Ranges study included the effect of total vegetation control, which indicated that diameters of Douglas-fir receiving total vegetation control tended to become more uniform over time in the Coast Ranges. An additional equation was developed to project quadratic mean diameter so that individual-tree diameters could be estimated from projected relative size. The effect of vegetation management treatments on projected quadratic mean diameters in the Siskiyou study was expressed as an interaction between proportion of cover removed by treatments (intensity) and dominant height of Douglas-fir at time of treatment relative to current dominant height. In 1- and 2-year projection periods, the stand table projection system performed similarly to a diameter distribution prediction system based on a Weibull distribution function. However, the difference between projected and predicted diameter distributions became more pronounced as the projection period increased to 5 years.

A parameter recovery procedure for the Weibull distribution function was modified to incorporate monocultures and mixtures of eastern cottonwood (Populusdeltoides Bartr.) clones planted in Mississippi and Kentucky. Components of the system included functions to predict stand-level basal area and four percentiles (0th, 25th, 50th, and 95th) of the cumulative diameter distribution. Basal area was predicted as a function of surviving number of trees, dominant height, age, planting location, and the proportion of each clone planted. Clonal proportions, which accounted for 3.6% of the variation in observed basal area, were more important than differences in planting locations, which accounted for 3.0% of the variation. Interactions between clones in mixtures were not significant (p = 0.5676), but some cases of both over- and under-compensation appeared to be developing. Percentiles of the cumulative diameter distribution were predicted as functions of quadratic mean diameter, and therefore included indirect effects of both genetic and planting site differences. Only the minimum diameter (D0) was directly affected by proportions of clones planted. Most of the monocultures and mixtures of clones had smaller minimum diameters than expected for a given value of quadratic mean diameter. The predicted quadratic mean diameter and percentiles were used to recover parameters of the Weibull distribution such that the predicted diameter distribution has the same quadratic mean diameter as obtained from the stand basal area model. The predicted distributions indicated that a common stand-level model was not sufficient for accounting for variations in diameter distributions of eastern cottonwood clones. As a result of the differences in diameter distributions, monocultures and mixtures of the Texas clones appeared to have less volume and greater stand variance than the Mississippi clones.

A parameter recovery procedure for the Weibull distribution function, based on diameter percentiles, was modified to incorporate the effects of interfering vegetation in young Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) plantations. The applicability of the system was tested by using data from sites in the Coast Ranges of Oregon and Washington and in the Siskiyou Mountains of southwestern Oregon. Four percentiles (0, 25th, 50th, 95th) of the cumulative probability distribution were predicted as functions of quadratic mean diameter and age. In the Siskiyou study, cover and total vegetation control affected quadratic mean diameter and all four percentiles; intensity of the vegetation treatments affected the 0 and 25th percentiles, and the interaction between intensity and timing of treatment affected quadratic mean diameter. In the Coast Ranges study, only quadratic mean diameter was affected by cover of woody vegetation, while quadratic mean diameter and the 25th percentile were significantly affected by total vegetation control. The predicted distributions showed decreasing variance with increasing cover, particularly in the Siskiyou Mountains. In the Coast Ranges study, the coefficient of variation increased with increasing cover, indicating that the variance of stem diameters was affected by average size. On xeric sites in the Siskiyou Mountains, high diameter variability in plots with total vegetation control suggests that interspecific competition may inhibit the expression of microsite variation.

Height, diameter, volume, and survival response of 4-yr-old loblolly pine (Pinus taeda L.) was compared for chemical and mechanical site preparation treatments. Early-summer (June) and late-summer (September) treatments were installed in separate randomized complete block experiments. Either Tordon K© or Tordon 101© in combination with Garlon© and the three-pass mechanical treatments provided the best growth and survival in the early-summer study, but Tordon 101 + Garlon 4 was the most cost-effective. The Tordon K-Garlon combination, Roundup©, and the two-pass mechanical treatments provided the best growth and survival in the late-summer study, with Tordon K + Garlon 4 being the most cost-effective treatment tested in the late summer study. Models were developed to predict mean height, diameter, and volume per acre from age, sum of crown heights for dogwood, natural pines, red oak, and sweet-gum, and an indicator for total vegetation control. Cover of the herbaceous components was negatively correlated with hardwood density, and did not significantly improve predictions of pine response. South. J. Appl. For. 16(2):99-105.

Prediction equations were developed for basal area and percentiles of diameter distributions to account for the hardwood component in site-prepared, Piedmont and Upper Coastal Plain loblolly pine (Pinus taeda L.) plantations. Unlike existing stand-level simulation models that incorporate hardwood competition, the new equations resulted in constant total basal area regardless of the amount of hardwood competition and permitted the variance of the diameter distribution to increase with increasing proportion of hardwoods. The equations presented can be used with existing dominant height, survival, and volume equations as a tool for assessing the impact of hardwoods on loblolly pine yield. South. J. Appl. For. 16(2):93-98.

A study was conducted to identify optimum picloram-triclopyr combinations for use on the following flatwoods species: gallberry (Ilex glabra [L.] Gray), saw palmetto (Serenoa repens [Bartram] Small), vacciniums (Vaccinium spp.), waxmyrtle (Myrica cerifera L.), fetterbush (Lyonia lucida [Lam.] K. Koch), staggerbush (Lyonia ferruginea [Water] Nutall), and sweetbay (Magnolia virginiana L). More than 70% control of gallberry, saw palmetto, vacciniums, waxmyrtle, and sweetbay was obtained with 4.0 lb a.e./ac of triclopyr alone. At least 1.0 lb of picloram combined with 1.0 lb or more of triclopyr was required to achieve 70% or greater control of fetterbush and staggerbush. The picloram formulation including 2,4-D (Tordon 101®) was more effective than the formulation without 2,4-D (Tordon K®) on saw palmetto, vacciniums and waxmyrtle. South. J. Appl. For. 15(4):187-193.

Chemical site preparation treatments were compared against each other and against mechanical treatments in a randomized complete block design. Two studies were conducted with spring (June) and late summer (September) treatment dates. Efficacy was measured 2 years after treatment as percent control on individually identified stems and as percent change per acre from subplot data. Combinations of Tordon K®, Tordon 101® mixture, Garlon 4®, Galon 3A®, Velpar L®, and Roundup® herbicides were tested.* For the spring study, combinations of Tordon + Garlon 4 herbicides effectively controlled red maple, dogwood, and red oaks. Tordon 101 + Garlon 4 was the most effective treatment on water/willow oaks. Among the treatment on sweetgum. Velpar L was the most effective treatment on water/willow oaks. Among the late summer applied treatments, Roundup provided the best overall control of the hardwood species examined. A shear, rake, and disk treatment provided comparable control to chemical treatments in the spring study, but at a higher cost. Double chopping was not an effective treatment in the late summer study. South. J. Appl. For. 14(1):24-32.

In Puerto Rico, where locally grown woods are primarily used for furniture and crafts production, estimation of wood volume makes it possible to estimate the monetary value of one of the many commodities and services forests provide to society. In the Puerto Rican forest inventories of 1980 and 1990, workers calculated stem volume directly by applying geometric formulae to bole sections of merchantable trees. Field crews recorded several diameter and height measurements along the bole of each tree. If tree volume estimates were based on fewer tree measurements, this would significantly increase field crew productivity. For this reason, tree volume equations have been derived from Puerto Rican forest inventory data by directly calculating stem volume, then creating regression equations that estimate inside and outside bark merchantable stem volume from tree diameter at breast height and total height.

Height-over-age curves and site-index prediction tables were derived using nonlinear polymorphic regression models with data from 25-year-old old-field plantations ranging from coastal North Carolina to southwestern Arkansas. Plots from heavy silty clay soils of the interior flatwoods of Mississippi exhibited height growth patterns noticeably different from the overall pattern. A separate table and set of curves were developed for such sites.

Volume equations of the form V = b0 + b1 D²H were developed to estimate total volume inside and outside bark for yellow-poplar (Liriodendron tulipfera L.) in the hilly Coastal Plain of Alabama. Volumes predicted using the outside-bark equation were determined to be different from those predicted by the comparable volume equation developed for southern Appalachian yellow-poplar. A nonlinear ratio model was developed to estimate the volume to any specified top diameter.

The effects of competition on loblolly pine (Pinus taeda L.) development during the initial 4 years of a plantation were investigated on an Upper Coastal Plain site in east-central Alabama. Height and diameter response to competition control in relation to time following treatment and amount of herbaceous competition were examined. Trees on plots receiving broadcast weed control for 2 years were twice the height and diameter of trees with no weed control after 4 years, while trees receiving banded weed control for 2 years were 1.6 times taller and 1.75 times larger in diameter. Broadcast and banded 1-year treatments were 1.4 times larger in both measures.