Incorporating the effects of interspecific competition and vegetation management treatments in diameter distribution models for Douglas-fir saplings

1992 ◽  
Vol 22 (9) ◽  
pp. 1255-1262 ◽  
Author(s):  
Steven A. Knowe ◽  
Timothy B. Harrington ◽  
Robert G. Shula
Keyword(s):  
Interspecific Competition ◽  
Douglas Fir ◽  
Diameter Distribution ◽  
Cumulative Probability ◽  
Quadratic Mean ◽  
Vegetation Control ◽  
Mean Diameter ◽  
Coast Ranges ◽  
Siskiyou Mountains ◽  
Quadratic Mean Diameter

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.

Effects of density control and fertilization on growth and yield of young Douglas-fir plantations in the Pacific Northwest

2007 ◽  
Vol 37 (2) ◽  
pp. 449-461 ◽  
Author(s):  
Yuzhen Li ◽  
Eric C. Turnblom ◽  
David G. Briggs
Keyword(s):  
Basal Area ◽  
Douglas Fir ◽  
Growth And Yield ◽  
Quadratic Mean ◽  
Stand Growth ◽  
Density Control ◽  
Mean Diameter ◽  
Quadratic Mean Diameter ◽  
Area And Volume ◽  
Effects Of Density

To examine the effects of density control and fertilization on stand growth and yield of young Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) plantations, seven treatment regimes were applied in sixty-three 9-year-old plots from nine installations across western Washington and Oregon. Fertilizer was applied at the rate of 220 kg N·ha–1 (as urea) at stand establishment and every 4 years thereafter. Results after 12 years showed that widely spaced stands exhibited significantly larger quadratic mean diameter than did narrowly spaced stands. The densest stands initially had the greatest overall stand basal area and volume, but accumulation rate in the dense stands had been declining with time. After 12 years, the less dense stands had met or exceeded the basal area periodic annual increment of dense stands. Across all densities, the periodic annual increments of quadratic mean diameter, basal area, and volume in fertilized plots were significantly greater than in unfertilized plots following the first and second urea applications. However, the first fertilization was insufficient to produce a significant increase in stand yield and the significant fertilization increases in yield were found following the second and the third urea applications. This study showed neither significant fertilization effect nor density effect on dominant height. In addition, no significant interactions were found for any stand growth and yield variables considered, but fertilization responses showed different trends among density treatments over time.

Eastern cottonwood clonal mixing study: predicted diameter distributions

1994 ◽  
Vol 24 (2) ◽  
pp. 405-414 ◽  
Author(s):  
Steven A. Knowe ◽  
G. Sam Foster ◽  
Randall J. Rousseau ◽  
Warren L. Nance
Keyword(s):  
Weibull Distribution ◽  
Basal Area ◽  
Diameter Distribution ◽  
Minimum Diameter ◽  
Quadratic Mean ◽  
Parameter Recovery ◽  
Eastern Cottonwood ◽  
Mean Diameter ◽  
Quadratic Mean Diameter ◽  
Diameter Distributions

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.

Properties of the quadratic mean diameter in balanced diameter distributions

1985 ◽  
Vol 15 (2) ◽  
pp. 474-476
Author(s):  
Donald J. Weatherhead ◽  
Roger C. Chapman ◽  
John H. Bassman
Keyword(s):  
Stand Structure ◽  
Basal Area ◽  
Tree Size ◽  
Diameter Distribution ◽  
Quadratic Mean ◽  
Growing Stock ◽  
Mean Diameter ◽  
Quadratic Mean Diameter ◽  
Stand Basal Area ◽  
Diameter Distributions

Balanced diameter distributions are widely used to describe stand structure goals for residual growing stock in uneven-aged forests. The quadratic mean diameter is frequently used as a descriptor of a balanced diameter distribution. In this paper the quadratic mean diameter is shown to be independent of stand basal area for balanced diameter distributions with a common class width, maximum and minimum diameters, and de Liocourt's q ratio. Additionally it is shown that the quadratic mean diameter is relatively insensitive to changes in maximum tree size and q ratios for q ratios 1.5 and larger.

scholarly journals Five-Year Thinning Response of an Overgrown Douglas-Fir Christmas Tree Plantation

2004 ◽  
Vol 19 (3) ◽  
pp. 171-174
Author(s):  
S. Hummel ◽  
R. Hummel
Keyword(s):  
Douglas Fir ◽  
Planting Density ◽  
Christmas Tree ◽  
Tree Plantation ◽  
Quadratic Mean ◽  
Density Area ◽  
Mean Diameter ◽  
Plantation Age ◽  
Quadratic Mean Diameter

Abstract A 15-year-old Douglas-fir Christmas tree plantation in western Oregon was thinned in 1996 according to regional sawtimber conversion guidelines. The plantation comprised two strata, distinguished by initial planting density (Area 1 = 5 × 5 ft and Area 2 = 10 × 10 ft). Unthinned control plots were established in both Area 1 and Area 2 at the time of the thinning treatment. Five years later, the quadratic mean diameter (QMD) in Area 1 (thinned) was 6.4 in. versus 5.2 in. in Area 1 (unthinned), while in Area 2 (thinned) the QMD was 11.4 in. compared to 9.3 in. in Area 2 (unthinned). Over the same period, the volume/ac in Area 1 (thinned) (1,080 ft3/ac) was nearly twice that of Area 1 (unthinned) (576 ft3/ac). In contrast, the volume/ac in Area 2 (thinned) (2,318 ft3/acre) was almost half that of Area 2 (unthinned) (4,264 ft3/ac). These results suggest that while thinning was timely for Area 1, the thinning treatment could have been delayed for Area 2. By plantation age 30, the treated units in Area 1 and Area 2 have estimated yields of 9.6 and 11.6 thousand bd ft (mbf), respectively, with no additional thinning. Given 2002 average prices for #3 sawmill grade logs, gross return at age 30 would range between $5,000 and $6,000/ac. West. J. Appl. For. 19(3):171–174.

A Stocking Guide for Southern Bottomland Hardwoods

1995 ◽  
Vol 19 (3) ◽  
pp. 103-104 ◽  
Author(s):  
J. C. G. Goelz
Keyword(s):  
Basal Area ◽  
Bottomland Hardwoods ◽  
Quadratic Mean ◽  
Mean Diameter ◽  
Quadratic Mean Diameter

Abstract A stocking guide was developed from the data of Putnam, et al. (1960). The form of the stocking guide follows Gingrich (1967), although the “B”-line is based on the suggested residual stocking of Putnam, et al. (1960) rather than on minimum full stocking. This stocking guide is similar to the stocking guide for central upland hardwoods constructed by Gingrich, except that 100% stocking is 5-7 ft2² of basal area lower for the southern bottomland guide, across a range of quadratic mean diameter. South. J. Appl. For. 19(3):103-104.

Compatible basal-area growth and yield model for thinned and unthinned stands

1983 ◽  
Vol 13 (4) ◽  
pp. 563-571 ◽  
Author(s):  
Robert L. Bailey ◽  
Kenneth D. Ware
Keyword(s):  
Loblolly Pine ◽  
Basal Area ◽  
Growth And Yield ◽  
Yield Model ◽  
Projection Model ◽  
Quadratic Mean ◽  
Basal Area Growth ◽  
Area Growth ◽  
Mean Diameter ◽  
Quadratic Mean Diameter

A measure of kind and level of thinning is developed and its relationship to other stand attributes such as number of trees, basal area, and volume removed in thinning is quantified. This measure or thinning index is based on the ratio of the quadratic mean diameter of thinned trees to the quadratic mean diameter of all trees before thinning. The thinning index is then logically incorporated into a thinning multiplier from which is derived a compatible basal-area growth projection model to generalize the previous concepts for thinning effects in systems for predicting growth and yield. Empirical tests with data from thinned and unthinned natural stands of loblolly pine, from thinned and unthinned slash pine plantations, and from thinned western larch stands show the model to provide estimates with improved properties. Hence, the thinning index and the thinning multiplier are also proposed for other situations involving effects of thinning.

Diameter and height distributions in genetically improved Pinus radiata

1998 ◽  
Vol 28 (2) ◽  
pp. 248-258 ◽  
Author(s):  
S D Carson ◽  
J D Hayes
Keyword(s):  
Pinus Radiata ◽  
Genetic Improvement ◽  
Diameter Distribution ◽  
Size Distributions ◽  
Quadratic Mean ◽  
Similar Tendency ◽  
Genetically Improved ◽  
Large Plot ◽  
Quadratic Mean Diameter ◽  
The Right

Diameter and height distributions for Pinus radiata D. Don trees grown from seed lots representing a range of genetic improvement were compared at midrotation (age 14 or 15) in seven large-plot trials at six sites. In one of the trials, comparisons were made at year 5 and annually from age 8 to 16. These are the first data from plantation conifers comparing tree size distributions of commercially planted seed lots. Differences among seed lots for quadratic mean diameter and mean height were statistically significant and generally reflected the expected level of genetic improvement. Standard deviation, skewness, and kurtosis were not significantly different among seed lots. However, diameter distributions of higher rated seed lots sometimes appeared very slightly more skewed to the right and flatter than the lower rated seed lots, a similar tendency observed as stands age. Models used to predict diameter distribution from stand parameters are not likely to require modification for genetically improved seed lots.

Partial Calibration of "ONTWIGS": A Forest Growth and Yield Projection System Adapted for Ontario

1994 ◽  
Vol 11 (2) ◽  
pp. 41-46 ◽  
Author(s):  
Bijan Payandeh ◽  
Pia Papadopol
Keyword(s):  
Basal Area ◽  
Forest Growth ◽  
Data Sets ◽  
Prediction Errors ◽  
Northern Ontario ◽  
Quadratic Mean ◽  
Tree Survival ◽  
Mean Diameter ◽  
Quadratic Mean Diameter ◽  
Stand Attributes

Abstract "ONTWIGS" (an adaptation of "LSTWIGS" for Ontario), was partially calibrated for permanent plots data sets from northern Ontario. Stand attributes used for calibration were quadratic mean diameter, number of trees, and basal area/ha. Simple local calibration was accomplished by adjusting tree survival and potential diameter growth coefficients so as to reduce the prediction errors to within 10% of the actual values over a 5-yr period. This resulted in prediction errors ranging from -9.9 to 6.9%, but with an overall average of only: -1.4, 1.0, and 0.2% for the spruce fir data; from -8.5 to 2.8%, but with an overall average of only -0.7, 0.5, and 0.4% for a black spruce drainage and fertilization experiment; and from -6.6 to 9.8%, but with an overall average of only -1.7, 0.0, and -1.8% for an unthinned red pine plantation for number of trees/ha, quadratic mean diameter, and basal area/ha, respectively. Results indicate that "ONTWIGS" may be locally calibrated through simple procedures to increase its prediction accuracy to ±5% of the observed stand attributes, averaging less than 3% for the major timber species in northern Ontario and for short to medium projection periods. However, the uncalibrated model should be used with caution for short terms, only and where no other projection tools are available. More extensive calibrations of "ONTWIGS" on larger and more representative data sets are currently underway. North. J. Appl. For. 11(2):41-46.

scholarly journals Development of Water Tupelo Coppice Stands on the Mobile-Tensaw River Delta for Five Years After Precommercial Thinning and Cleaning

2001 ◽  
Vol 25 (4) ◽  
pp. 165-172 ◽  
Author(s):  
J.C.G. Goelz ◽  
J.S. Meadows ◽  
T.C. Fristoe
Keyword(s):  
Basal Area ◽  
Individual Tree ◽  
Quadratic Mean ◽  
Precommercial Thinning ◽  
Mean Diameter ◽  
Water Tupelo ◽  
Rotation Age ◽  
Large Water ◽  
Quadratic Mean Diameter ◽  
The Individual

Abstract Three 4-yr-old stands (or locations) were selected for treatment. Treatment consisted of two components: (1) thinning water tupelo (Nyssa aquatica L.) stump sprouts and (2) cutting all stems of Carolina ash (Fraxinus caroliniana Mill.) and black willow (Salix nigra Marsh.) (cleaning). Contrary to results in other areas, survival of water tupelo coppice was very high and was not affected by the treatments. Cleaning had little or no positive effect on the individual tree or stand-level variables we measured. Thinning sprout clumps significantly increased diameter growth of water tupelo; the effect of thinning was considerably larger for one location. Stand basal area growth was decreased by thinning sprout clumps. However, quadratic mean diameter was increased by thinning, particularly at one location. Although thinning decreased basal area 5 yr after treatment, the increase in quadratic mean diameter was sufficient for there to be no significant effect of thinning on total volume 5 yr after treatment. Because of this, and in anticipation of imminent natural thinning of the unthinned plots, we suspect that the thinned plots will eventually have significantly greater standing volume than the unthinned plots, at least for the location where density of large sprouts was initially the highest. Rotation age will be decreased for that stand because stems will achieve merchantable size sooner. Thus we consider precommercial thinning of sprout clumps to be a potentially effective practice in stands with a high density of large water tupelo sprouts. South. J. Appl. For. 25(4):165–172.

Toward developing a direct relation between gross volume increment and stand density

2013 ◽  
Vol 43 (9) ◽  
pp. 852-860 ◽  
Author(s):  
Thomas J. Dean ◽  
Scott D. Roberts ◽  
Robert S. Seymour
Keyword(s):  
Loblolly Pine ◽  
Stand Density ◽  
Height Increment ◽  
Individual Tree ◽  
Red Alder ◽  
Quadratic Mean ◽  
Stem Size ◽  
Mean Diameter ◽  
Volume Increment ◽  
Quadratic Mean Diameter

A general form for expressing gross volume increment in terms of stand density is derived and tested with data from spacing trials in red alder (Alnus rubra Bong.), eastern white pine (Pinus strobus L.), longleaf pine (Pinus palustris Mill.), and loblolly pine (Pinus taeda L.). The equation relates the stand sum of individual-tree volume increment per metre height increment to a power function of quadratic mean diameter times tree density. The proposed equation fit the data best when the model included an intercept. Within each species, the fits were unbiased with respect to the independent variables, plantation age, and site height, and with the exception of the youngest ages for red alder and loblolly pine, they were unbiased with respect to the plot sums of individual-tree volume increment divided by individual height increment. Exponents estimated for quadratic mean diameter for each species ranged from 1.58 to 1.80. The resulting equations indicate a linear relationship between the stand sum of individual-tree volume increment per metre height increment and stand density. Scattergrams of gross-volume increment per hectare per year and stand density can be recovered by multiplying the predicted values of the regressions by Lorey’s height. The regressions support the hypothesis that each metre of height growth produces consistent changes in stem size, regardless of initial tree size, age, or site quality, and implies that the change in stem size is a predictable power function of stem diameter for an individual tree or quadratic mean diameter for a stand.

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