No abstract

The development of a system of equations that model the growth and development of even-aged natural shortleaf (Pinus echinata Mill.) pine forests is described. The growth prediction system is a distance-independent individual-tree simulator containing equations that predict basal-area growth, survival, total and merchantable heights, and total and merchantable volumes for shortleaf pine trees. These equations were combined into a computer simulation program that predicts future states of shortleaf pine stands from initial stand descriptions. Comparisons of observed and predicted ending stand conditions in shortleaf pine research plots indicate the simulator makes acceptable forecasts of final stand attributes. South. J. Appl. For. 23(4):203-211.

Interpolated cubic splines were used to estimate diameters and partial or total volumes for 285 trees from Pinustaeda L. plantations in southern Brazil. A range of 4 to 13 interpolated points was tested in an attempt to determine how many points are necessary to adequately represent stem taper. The various number of combinations with 13 or fewer points for interpolation were compared with a full spline of 16 points, which according to pertinent literature, estimates volume similarly to the traditional volume formulas (Newton, Huber, Smalian). The results showed that 10 well-placed points are necessary to obtain reliable estimates of diameter and partial or total volume along the entire stem. If the top 15% of the stem is ignored, 5 points adequately estimate volume, with an average residual of less than 2%. However, when fewer than 7 points are used, placement of points is very important to avoid illogical oscillation inherent in the use of cubic splines.

A total of 141 paired plot installations remain of the 160 that were planted with slash (Pinus elliottii Engelm.) and loblolly (P. taedaL.) pine across southeastern Georgia and northern Florida, after 14 growing seasons. Installations were evenly distributed across eight soil types. Analyses indicate that loblolly performed equal to or better than slash pine. There were no soil X species interactions. After 14 yr, loblolly pine had significantly higher survival (71% vs. 66%), stand basal area (98 vs. 81 ft2/ac), total stand volume (1857 vs. 1721 ft3/ac), merchantable stand volume (1497 vs. 1310 ft3/ac), total green weight (53 tons vs. 47 tons), and merchantable green weight (45 vs. 35 tons/ac) than slash pine. Growth over the period from age 11 to age 14 was also higher for loblolly than for slash indicating that the difference in the two species is diverging over time. South. J. Appl. For. 24(1): 31-36.

Several mortality functions were examined to develop useful equations to predict early seedling survival of site-prepared loblolly pine plantations in the Georgia Piedmont region. Models were developed to predict surviving trees per acre at age 5 from stand initiation, as well as from age 1, under optimal planting and handling practices. The models performed reasonably, predicting surviving trees per acre at age 5 with an average absolute prediction error of 9.2% and 1.9% respectively. The age 1 to age 5 model was also found to perform reasonably on operational plantings with an average absolute prediction error of 3.3% for the study data. The models could be used to obtain starting densities for existing mortality models used in long term planning, or to predict the success of stand establishment after the first growing season. South. J. Appl. For. 20(4):197-202.