Modeling the Effects of Initial Spacing on Stand Basal Area Development of Loblolly Pine (original) (raw)
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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.
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.
Modeling individual tree growth for juvenile loblolly pine plantations
Forest Ecology and Management, 1996
Modeling juvenile growth of loblolly pine plantations is important for a better understanding of the whole process of stand development and helping to schedule appropriate silvicultural treatments for young stands. This paper evaluates spacing treatment effects on young loblolly pine trees and presents individual tree growth models for loblolly pine plantations. Using data from spacing trials (plot size ranging from 1.22 X 1.22 to 3.66 X 3.66 m2) for loblolly pine plantations, a generalized randomized block design (GRBD) analysis was conducted to test spacing treatment and site quality effects on young tree growth. It is shown that planting density and site quality have significant influence, and spacing rectangularity is negligible. Based on the Bertalanffy differential equation and biologically reasonable assumptions regarding density and site quality effects on tree growth, a general projection model for individual tree diameter and height was developed. A stochastic model for generalizing tree height predictions within each diameter class was proposed. Models for crown ratio, and initial diameter distribution were also developed. The models were estimated with spacing trial data from young loblolly pine plantations. Validation results for these models showed that they are appropriate for predicting the juvenile growth of loblolly pine plantations where competing vegetation has been controlled in a similar manner to these spacing trials.
The effects of spacing and thinning on stand and tree characteristics of 38-year-old Loblolly Pine
Forest Ecology and Management, 2000
The effects of early and continuous density control on tne characteristics of mature loblolly pine (Pinus tuedu L.) were measured at age 38 and analyzed. Trees in plots planted at spacings of 1.8x 1.8, 2.4x2.4, 2.7x2.7, 3.0x3.0, and 3.7x3.,7 m were either left unthinned or thinned every 5 years beginning at age 18, to residual basal areas of 27.5, 23.0, 18.4, and 13.8 m2 haa'. Trees thinned from plot buffer zones at age 38 were selected to represent a final harvest cross-section of each treatment for evaluation of bole form, component biomass, ;and crown architecture. Volume and biomass of cut trees from all thinnings were included with the age 38 data for stand level yield comparisons. Results show thinning effects were generally more pronounced than spacing effects. Trees of the same diameter at breast height and total height from heavily thinned stands had more cylindrical lower boles, more upper stem taper, longer crowns with more and larger branches, more total foliage, and hence more biomass than trees from unthinned or lightly thinned stands. All levels of thinning increased the yield of the stand in terms of foliage and branch biomass, while only light or moderate thinning increased bole biomass and volume yields. 'The magnitude of these differences are presented. 0 2000 Elsevier Science B.V. All rights reserved. fed.us (V.C. Baldwin Jr.). and stand growth and yield and tree form in planted and natural stands of different densities (e.g. USDA, Forest Service, 1929; Mann and Dell, 1971; Burkhart et al., 19X7), information regarding the morphology and yield differences in older plantations is lacking. We analyzed standing-tree measurements and intensive felled-tree measurements (of thinned trees) at age 38 of a long-term, loblolly pine growth and yield study. Our objective was to show the effects of initial planting spacing and thinning (1) on biomass and volume 0378-l 127/00/$ -see front matter 0
Forest Science, 2014
The growth dynamics of a tree may be affected by different silvicultural treatments of the stand, such 16 as thinning or fertilization. A proper analysis of such effect at tree level should take into account the 17 nuisance caused by age-driven growth dynamics, tree-and site-specific growth pattern and the growth 18 conditions of the calendar year. In this context, we analyzed the growth response of individual Scots 19 pine (Pinus sylvestris L.) trees to thinnings of varying intensity. We first determined basal areas of 20 annual rings from pith to bark at 1.3 m above stem base for a total of 88 sample trees, based on ring 21 density profiles measured using an X-ray microdensitometer. Second, a linear mixed-effects model 22 29 size of the tree before thinning. The thinning response started a slow decrease few years after reaching 30 the maximum. The observed mechanism on the effects of tree size and thinning intensity on the tree-31 level response might generalize to other locations and tree species, too. The applied method 32 demonstrates the applicability of the linear and nonlinear mixed-effects modeling for the analysis of 33 treatment response on individual tree growth and dynamics of the response. A similar approach could 34 be used to analysis of other longitudinal treatment data as well.
Modeling the impact of thinning on height development of dominant and codominant loblolly pine trees
Annals of Forest Science, 2006
Data collected from loblolly pine thinning study plots established in plantations on cutover, site-prepared lands were used to evaluate thinning impact on height growth of dominant and codominant loblolly pine trees. Height growth was reduced initially by thinning but was increased after 3 years following thinning. The average total height of dominant and codominant trees in thinned stands exceeded its counterpart in unthinned stands 12 years after thinning. Initial growth response to thinning was less at older stand ages than at younger ages. A model was constructed to characterize the development of height in thinned and unthinned stands. This model reflects the initial suppression of dominant and codominant height growth followed by an acceleration as a result of thinning.
Nonlinear mixed modeling of basal area growth for shortleaf pine
Forest Ecology and Management, 2008
Mixed model estimation methods were used to fit individual-tree basal area growth models to tree and stand-level measurements available from permanent plots established in naturally regenerated shortleaf pine (Pinus echinata Mill.) even-aged stands in western Arkansas and eastern Oklahoma in the USA. As a part of the development of a comprehensive distance-independent individual-tree shortleaf pine growth and yield model, several individual-tree annual basal area growth models were filled It) the clata with the objective ofsclccling Ihe model thaI has superior fll to the data as well as attributes suitable for praclical application in shortleaf pine stand simulator useful as an aid in forest management decisionmaking. The distance-independent individual-tree model of Lynch et al. lLynch , T.B., Hilch, K.L. , Huebschmann, M.M., Murphy, P.A., 1999. An individual-tree growth and yield prediction system for even-aged natural shortleaf pine forests. South. J. App\. For. 23, 203-21 II for annual basal area growth was improved to incorporate random-effecls for plols in a potential-modifier framework with st;1nd-Ievcl and tree-level explanatory variables. The fitted mixed-effects models were found to fit the data and to predict annual basal area growth better than the previous model forms fitted using ordinary least-squares. There was also some evidence of heterogeneous errors, the effects of which could be corrected by using a variance function in the estimation process. The revised parameter estimates from the selected mixed model could be utilized in a growth ancl yield simulator that also takes appropriate dbh-height and mortality functions into account. (f)
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.