Site index curves and yield predictors for three species in the vicinity of Norris Lake

In the late 1930's, L. S. Minckler established eight planting experiments on abandoned fields in the vicinity of Norris Lake. These plantings included 700 plots with 11 hardwoods and 3 conifers on 167 acres. In 1968 G. W. Smalley evaluated the condition of the 30-year-old plantations and initiated a growth and yield study of shortleaf pine (Pinus echinata Mill.), eastern white pine (P. strobus L.), and yellow-poplar (Liriodendron tulipifera L.). This study included 66 plots on three soil parent materials (limestone, dolomite and shale) and two aspects (north and south). In the early 1970's, all of the shortleaf pine and six of the white pine plots were destroyed by southern pine bark beetles (Dendroctonus frontalis Z.). The remaining white pine plots and the yellow-poplar plots were remeasured at plantation age 46.

The diameter at breast height (dbh) and total height were measured on each of the plots to estimate per acre number of stems, basal area, total cubic-foot volume, merchantable cubic-foot volume, mean dbh and average height of dominants and codominants at each measurement age. These estimates were analyzed by parent material and aspect for each of the three species.

At plantation age 30, shortleaf pine height growth was less on shale soils than on dolomite and limestone, though stand volume was not affected by parent material. Mortality of white pine at plantation age 30 was highest on shale soils and northern slopes, though stand volume was not affected by either variable. At plantation age 46 white pine yield was best on dolomitic northern slopes and poorest on dolomitic southern slopes. Growth of yellow-poplar was best on shale soils and poorest on dolomitic sites; aspect did not significantly effect any stand attributes. White pine had the greatest mean volumes of the three species and yellow-poplar had the least.

Total cubic-foot yield and yield to a 4-inch top (outside bark) were predicted for white pine and yellow-poplar from site index, basal area, and age in years from seed. Additionally, a prediction equation for cubic-foot yield to a 3-inch top (outside bark) for white pine was developed and compared to a published equation. The published equation for white pine overpredicted yield at 32 years from seed and underpredicted yield at 48 years from seed. The equation for yellow-poplar total yield was also compared to a published equation. The published equation for yellow-poplar overpredicted yield at 31 years from seed and underestimated yield at 47 years from seed.

Stem analysis was conducted on one white pine per plot at 32 years from seed and the height to each whorl was measured on two white pine per plot at 48 years from seed. These data were used to construct site index curves with base age 25 (years from seed) for white pine. Stem analysis was also conducted on one yellow-poplar per plot at 31 years from seed and total height at 47 years from seed was measured on ten trees per plot. These data were used to construct site index curves with base age 25 (years from seed) for yellow-poplar. The curves for white pine and yellow-poplar were compared to published curves which underpredicted heights at ages less than 25 years and overpredicted heights at older ages.