Crown and basal area relationships of open-grown southern pines for modeling competition and growth

Abstract

Data were collected on open-grown loblolly pine (Pinustaeda L.), longleaf pine (Pinuspalustris Mill.), and shortleaf pine (Pinusechinata Mill.) and analyzed to provide predictive equations of crown width and maximum potential basal area growth for crown competition and growth and yield models. The measurements were taken on 115 open-grown loblolly pine trees and 76 shortleaf pines in southeastern Arkansas. The longleaf pine data consisted of 81 open-grown trees from southern Alabama, Georgia, and Florida. A circle and an ellipse were tested as geometric models of the vertically projected crown. No significant differences between the tree shapes were found based on analyses of length and azimuth of the largest crown diameter, and the circle was chosen as an appropriate model. This indicated that only the distance between trees, not their orientation to one another, need be included in models of crown competition based on crown contact. Predictive equations of mean crown width based on diameter at breast height were fitted for each species for use in models of crown competition. A Chapman–Richards growth rate function with an intercept term was fit to periodic annual inside-bark basal area growth based on initial inside-bark basal area to provide empirical estimates of maximum basal area growth rates for growth and yield modeling of the given species. Additionally, equations to predict double bark thickness as a function of diameter at breast height were fit for each species to facilitate the use of the equations with outside-bark measurements of diameter.

Onset of canopy closure for black pine, Turkish red pine and Scots pine forests

“…Hasenauer (1997) observed relationships between CW and DBH of open-grown Scots pine and black pine in Austria, however, their intercepts for both species were negative. Smith et al (1992) stated that the relationship between CW and DBH should have a positive intercept, as it was obtained when curvilinear and power models were used in this study (Table 3). On the other hand, Hasenauer (1997) stated that a logarithmic model improved the error structure significantly.…”

“…Ek (1974) used a power model for the CW-DBH relationships for Eastern white pine (Pinus strobus Linnaeus). In a similar study, Smith et al (1992) found out a curvilinear relationship between CW and DBH for loblolly pine (Pinus taeda Linnaeus) in the USA. Hasenauer (1997) observed relationships between CW and DBH of open-grown Scots pine and black pine in Austria, however, their intercepts for both species were negative.…”

“…It should be noted that age and site quality have no influence on the relationship between DBH and CW of open-grown trees (Chisman, Schumacher 1940). Trees with straight trunk and uniform crown were selected as suggested by Smith et al (1992). When a sign of inter-tree competition was suspected (for example, if there was an old stump near the measured tree), the open-grown tree was cored to see if any growth suppression occurred during the lifespan of the tree.…”

“…Data collection and model selection. The maximum crown width (CW max ) and DBH of open-grown Turkish red pine, black pine and Scots pine trees were recorded as suggested by Smith et al (1992). First, the widest part of the crown (i.e.…”

“…In other words, relationships which are very strong between crown width (CW) and DBH of open-grown trees are used to determine the D OCC . Age and site quality are not recorded (Smith et al 1992) since these variables have no influence on tree area (Chisman, Schumacher 1940;Gingrich 1967).…”