Modeling individual tree growth for juvenile loblolly pine plantations (original) (raw)
Related papers
Modeling the Effect of Density on the Growth of Loblolly Pine Trees
Southern Journal of Applied Forestry
Data from a set of loblolly pine spacing trials that have reached 16 yr since establishment were used to evaluate the effect of spacing on loblolly pine tree growth and stand development. Mean responses for six variables were evaluated: height, dbh, crown ratio, crown length, crown width, and survival. All response variables were affected by density, with dbh being the most affected and height the least affected over the 16 yr period. The rectangularity, or shape, of the growing space was not a significant factor in the development of any of these response variables. Models were constructed to characterize the development of the six response variables extrapolated over typical plantation rotation lengths of loblolly pine.
Regional mixed-effects height–diameter models for loblolly pine (Pinus taeda L.) plantations
European Journal of Forest Research, 2007
A height-diameter mixed-effects model was developed for loblolly pine (Pinus taeda L.) plantations in the southeastern US. Data were obtained from a region-wide thinning study established by the Loblolly Pine Growth and Yield Research Cooperative at Virginia Tech. The height-diameter model was based on an allometric function, which was linearized to include both fixed-and random-effects parameters. A test of regionalspecific fixed-effects parameters indicated that separate equations were needed to estimate total tree heights in the Piedmont and Coastal Plain physiographic regions. The effect of sample size on the ability to estimate random-effects parameters in a new plot was analyzed. For both regions, an increase in the number of sample trees decreased the bias when the equation was applied to independent data. This investigation showed that the use of a calibrated response using one sample tree per plot makes the inclusion of additional predictor variables (e.g., stand density) unnecessary. A numerical example demonstrates the methodology used to predict random effects parameters, and thus, to estimate plot specific height-diameter relationships.
Forest Science, 1992
A•STRACT. The prediction performance of eight height-diameter regression models was compared for estimating mean stand height when fitted to data selected from 175 1oblolly pine (Pinus taeda) sample plots by (i) simple random sampling without replacement, and (ii) stratified random sampling with dbh classes acting as strata. Among the models tested, the nonlinear model of the form H = ae a/ø performed best especially when fitted to data selected by simple random sampling. A small gain in precision obtained by stratification into dbh classes was outweighed by a substantial increase in bias due to the arbitrary allocation of numbers of sample trees to the strata. To update existing height-diameter models, it is recommended that new trees be selected and measured on every occasion instead of retaining the same sample trees used previously for model fitting. FOI•. Scl. 38(1):192-198. ADDITIONAL KEY WORDS. Inventory, height estimation, regression analysis, Pinus taeda. 192/FOP, ESTSCmNCE CITED BASKERVILLE, G.L. 1972. Use of logarithmic regression in the estimation of plant biomass. Can. J. For. Res. 2:49-53. CURTIS, R.O. 1967. Height-diameter and height-diameter-age equations for second growth Douglasfir. For. Sci. 13:365-375. EK, A.R. 1973. Performance of regression models for tree height estimation with small sample sizes. P. 67-80 in Statistics in forestry research, Proc. 4th Conf. Advisory Group of For. Stat., Vancouver, BC. FLEWELL•NG, J.W., and L.V. PmNAAa. 1981. Multiplicative regression with lognormal errors. For. Sci. 27:281-289. GREEN, E.J. 1981. Models of stand basal area distributions, individual tree basal area growth, and FEBRUARY 1992/ 197 height-diameter relationships for lobIdly pine. Ph.D. diss., Va. Polytechnic Inst. & State Univ., Blacksburg.
Modeling the Effects of Initial Spacing on Stand Basal Area Development of Loblolly Pine
Forest Science, 2012
Several studies have reported that in loblolly pine stands with high initial density, basal area declines after reaching maximum carrying capacity. This behavior is not reproduced by most basal area development models because the functions used are sigmoid and nondecreasing, tending toward an asymptote. We used a combined exponential and power function to model the impact of initial density on the basal area development of loblolly pine in a spacing trial. The combined exponential and power function is sufficiently flexible to describe both the asymptotic behavior of the wider initial spacing plots and the decrease in basal area after culmination of the closer spacings. We modified the original function to account for the time lag between stand establishment (age ϭ 0) and basal area establishment (age Ͼ 0), by allowing the origin of the function to be different than age ϭ 0. Two final models are presented: a model fitted using the population-average (PA) approach and a model fitted using the mixed-effects (ME) approach. At the fixed-effects level, the PA and ME models are not equivalent, and, therefore, the appropriate model should be selected according to the availability of previous data and the objectives of the prediction. If previous observations are available, they can be used to improve the predictions using the ME model. FOR. SCI. 58 :95-105.
Effects of initial spacing on height development of loblolly pine
The relationship between dominant height and age is the base of site index, the most widely used measure of site quality. In applying the site index concept, one typically assumes that height development is not affected by stand density or thinning treatment. This assumption has been challenged by recent studies on loblolly pine. A detailed data set with initial densities ranging from 6,730 to 750 trees/ha and covering ages 1 through 25 after plantation establishment was used to study and model the effect of initial spacing on height development of loblolly pine. Dominant height was found to be dependent on initial spacing. Height-age models are proposed that take into account the effect of spacing on average and dominant height. The differences among plantation densities are evident from age 6 and are consistent to the end of the 25-year period of study. Previous studies in other conifers have reported an early advantage in terms of height growth in denser stands that tend to disappear with age, producing a crossover of the growth trajectories. No evidence of this crossover effect in height was found. FOR. SCI. 57(3):201-211.
Growth-Density Relationships in Loblolly Pine Plantations
Forest Science, 2018
An understanding of relationships between stand volume growth and stand density is important for making informed management decisions. Contradictions concerning these relationships have been attributed to differences in definitions of volume growth and stand density, among other pitfalls. Models were developed to test growth-density relationships using past-growth data from three thinning studies in 11-to 41-year-old loblolly pine (Pinus taeda L.) plantations. Relationships between gross growth and stand density measures of basal area per hectare, stand density index, volume per hectare, and relative spacing were compared. Relative growth-density relationships were also compared by relating the growth and density of thinned plots to unthinned plots. Analyses indicated that gross volume growth increases with increasing stand density when accounting for age, quadratic mean diameter, and site quality. Results from relative growth-density relationships suggested that thinned stands can exhibit increased growth at relatively lower densities compared to that of an unthinned stand on a similar site. The fitted models, across all four density measures, indicated ever-increasing gross volume growth with increasing stand density within the range of observed data for loblolly pine plantations.
Young Modeling for I lntensi Loblolly Pine Plantations in Southeastern U S
2005
Intensively managed loblolly pine stands are often subjected to a variety of silvicultural treatments at t ime of planting or shortly thereafter. However, most loblolly pine growth-and-yield models predict growth after crown closure has occurred. In this article, we describe the development and implementation of a system of equations designed to simulate growth of loblolly pine before the onset of intraspecific competition. Treatment response functions were also developed for various site pre'paration, herbaceous weed control, and fertilization practices. These functions modify the baseline model predictions to simulate the effects of treatments on tree growth and stand development. This system was incorporated into the PTAEDAZ growth-and-yield simulator to make growth projections f rom time of planting through rotation age for intensively managed stands of loblolly pine in the southeastern United States. Growth simulations specifying either bedding or disking showed increases i...
Spacing rectangularity effect on the growth of loblolly pine plantations
Canadian Journal of Forest Research, 2002
The effect of spacing rectangularity on tree growth and stand development was evaluated using tree data obtained annually from a loblolly pine (Pinus taeda L.) spacing trial monitored through age 16 years. In this trial, plots with an initial planting density of 2240 trees/ha occur at slightly and highly rectangular spacings. Spacings with rectangularities 3:4 and 1:3 were used to evaluate the rectangularity effect. Survival and the development of height, diameter, volume per hectare, and basal area per hectare of loblolly pine trees were not affected by rectangularity. Diameter and height distributions were found to be a function of age but not a function of the rectangularity of initial spacing. Crown width, however, was affected by rectangularity. The crown width was larger at larger row or column distance than at smaller row or column distance, but the ratio of crown widths between and within rows was not equal to the rectangularity of the original planting spacing.
Modeling tree growth in fertilized midrotation loblolly pine plantations
Forest Ecology and Management, 1998
Diameter and height growth models for fertilized loblolly pine stands were developed using data from midrotation loblolly pine plantations across the southeastern United States. Tree growth in fertilized stands was predicted with a reference growth model multiplied by an equation predicting the relative growth response following fertilization. The temporal distribution of the growth response was modeled by the Weibull function. These equations for fertilizer growth response were developed to be compatible with individual-tree simulation models. Information about dose, nutrient elements, and time elapsed since fertilization are needed to predict the relative growth response following fertilization. q 1998 Elsevier Science B.V.