Curtis L. VanderSchaaf

Effect of planting depth on growth of open-rooted Pinus elliottii and Pinus taeda seedlings in the United States

Synopsis Three studies in the Coastal Plain of Georgia were remeasured 7 or 8 years after planting to determine the effects of planting depth on field performance of open-rooted seedlings [root-collar diameter (RCD) ≤ 5 mm]. Average planting depth (i.e, shoot height before planting minus shoot height above ground after planting) for machine planted P. elliottii was 14 cm while hand-planted P. taeda seedlings averaged 9-11 em deep. P. taeda showed no adverse effects on growth when planting seedlings up to 15 em deep. Data for machine planted P. elliottii indicated that seedlings were planted 9 mm deeper on double-beds than on single-beds. Small-diameter pine seedlings < 5mm RCD) were not planted as deeply as seedlings with large diameters (RCD ≥ 5 mm). For P. elliottii planted on double-beds, seedlings planted more than 15 em deep had slightly smaller diameters at breast height than seedlings planted 10 em deep. Although most tree planting guides recommend planting seedlings 7,5 em deep or less, many company plantations have been established by planting at greater depths.

Realized Gains from Planting Pinus taeda in 6.1 Meter Rows in Alabama

Pinus taeda L. plantations in the United States are typically established using rows that are spaced 3 to 4 m apart. Although one company now plants pines in 6.1 m rows, reports on performance using this row spacing are rare. This paper provides a case study (established at the Solon Dixon Forestry Education Center) that compares two densities (672 vs 1344 seedlings per ha (SPH)) when fixing the between-row distance to 6.1 m and using either 2.44 m or 1.22 m within-row distances between the planted trees. At age 13-years, the aboveground biomass mean annual increment on this old-orchard site was 13.5 green Mg/ha/yr. Planting half as many pine seedlings as typical (for this region) did not reduce dominant height (P=0.22), basal area/ha (P=0.58) or total merchantable tonnes/ha (P=0.67). As expected, the higher density produced trees that were smaller in mean diameter at breast height DBH (25 vs 22 cm) and had more pulpwood than 672 SPH plots. However, planting pines 1.2 m apart within the row reduced survival, soon after two severe summer droughts. Apparently this stress increased the risk of attracting bark beetles. An economic analysis indicates that 672 SPH produced more valuable timber (at age 13 years) and had the highest Net Present Value (NPV). In contrast, the Ptaeda3 model indicated 1344 SPH would have the greater NPV. The conflicting results are related to Ptaeda3 predicting one sawtimber-sized tree while 156 were present in the 672 SPH plots. Although these findings should not be extrapolated to cutover sites, it appears there may be several advantages to planting pines in wider than traditional rows. The reluctance to plant Pinus taeda in 6.1 rows on flat, agricultural lands might be due to a lack of field data and/or a reliance on output from growth and yield programs that were developed using data from cutover sites.

Reforestation Costs can be decreased by lowering initial stocking and outplanting morphologically improved seedlings

Two stock types of loblolly pine (Pinus taeda L. [Pinaceae]) were outplanted at 3 spacings: 749, 1122, and 1497 trees/ha (303, 454, and 605 trees/ac). Morphologically improved seedlings were grown at a density of 177/m2 (16/ft2) while standard seedlings were grown at a density of 277/m2 (25/ft2). Morphologically improved seedlings had an average root-collar diameter of 6.3 mm at time of outplanting and, after 3 y in the field, were taller and had more volume/ha than standard seedlings (4.5-mm root-collar at outplanting). An economic analysis was conducted based on 20-y volume estimates from a growth and yield program. If seedling cost is increased by 0.7 cent (due to growing at a low seedbed density) then outplanting cost per ha can be reduced by outplanting 750 morphologically improved seedlings instead of 1500 standard seedlings. Overall establishment costs might be reduced by US

The Weighted Least Squares Method Affects the Economic Rotation Age of Loblolly Pine - Two Planting Density Scenarios

108/ha (

EARLY GROWTH RESPONSE OF SLASH PINE TO DOUBLE-BEDDING ON A FLATWOODS SITE IN GEORGIA

44/ac) and the net present value of the stand might be increased by 10% or more (due to increasing the production of sawlogs). From this and other analyses, we determined that an important economic relationship exists between outplanting density and seedling quality.

Rectangular Spacing: An Economic Benefit?

Managers are typically interested in using equations that provide accurate volumes for large, merchantable trees while modelers are often more interested in equations that meet statistical assumptions. Therefore, modelers often use weighted (WLS) rather than ordinary least squares (OLS) to fit individual tree volume equations since the random error variance is not constant. Since OLS and WLS produce different parameter estimates, perhaps the method chosen will impact the predicted optimum economic rotation age. To address this concern, individual tree volumes were obtained from plots established in an unthinned loblolly pine plantation in southeastern Arkansas. Parameters of the combined- variable function were then estimated using OLS and WLS for the same dataset. Stand-level projections and predicted diameter distributions for two planting densities (748 and 2,692 seedlings per hectare) were then obtained from a growth and yield model (PTAEDA 3.1) and individual tree volumes were predicted using the two parameter estimation approaches. When conducting economic analyses, we found the optimum rotation age between OLS and WLS can differ by as much as 11 yrs (i.e. 10 yr clearcut vs 21 yr clearcut).