Field Studies
The following paragraphs summarize six field studies recently completed or currently being maintained and measured by the Forest Modeling Research Cooperative.

Data Collection in Plots Established with Enhanced Genetic Material
The FMRC has installed permanent plots in young operational stands established with clonal material. A total of 42 coastal plain locations in FL, AL, GA, NC, and SC were established during 2010 - 2011 and initial measurements of dbh, height and stem quality assessments collected. Stand ages at time of plot establishment ranged from 2 to 5 years. Remeasurements of these plots are occurring on a two-year cycle. Plans going forward call for keeping these plots as controls and pairing each with a thinned plot that will be established at the time the surrounding stand is thinned. An additional set of plots with the same clones is being installed in the Western Gulf region during the 2018-2019 period. This data collection work is part of an overall effort to build a database from which to study the development of trees and stands established with enhanced genetic material.

Regionwide Intensively Managed Plantation (IMP) Study
From 1996-1999 the Cooperative installed permanent remeasurement plots in intensively managed loblolly pine plantations across the native range of the species. Similar in scope and purpose to the regionwide thinning study, these plots are providing a regionwide data base for constructing growth and yield models applicable to managed plantations where silvicultural options such as site preparation, planting genetically improved seedlings, fertilization and weed control have been applied. At each location, an untreated control plot and two treatment plots have been established. Thinning and pruning treatments have been applied to the treatment plots at an appropriate time during stand development.

Pruning Studies
In the Spring of 2000, two pruning studies were established at two locations in the Virginia Piedmont. The first study, called the Early Tree Pruning (ETP) study, is designed to determine if early pruning induces an early age of formation of mature wood in loblolly pine trees. A randomized complete block design has been used with five treatments:

  • Prune half of the green crown at age 3
  • Prune half of the green crown at age 6
  • Prune half of the green crown at age 9
  • Prune half of the green crown at ages 3, 6, and 9

Pruning treatments through age nine have been applied. Measurements of dbh, total height, height to live crown and crown width were collected through age 12. In the 2014 - 2015 dormant season wood samples were collected from sample trees felled from each plot. From the wood samples, specimens were milled and subjected to x-ray scanning to study the effects of pruning on wood density.

The second study, called the Some Tree Pruning (STP) study, is designed to determine the effect of pruning intensity on the growth of loblolly pine trees. A randomized complete block design has been used with five treatments:

  • Remove ¼ of green crown on all trees
  • Remove ½ of green crown on all trees
  • Remove ¼ of green crown on half of trees
  • Remove ½ of green crown on half of trees

Pruning treatments were applied during the 2005-2006 dormant season six years after plot establishment. Measurements of dbh, total height, height to live crown and crown width were collected on a regular basis. A summary of the growth results from both studies have been published.

RW-19 Installation on the Virginia Piedmont
Coop personnel worked closely with the Forest Productivity Cooperative and the Virginia Department of Forestry to establish a RW-19 trial on the Appomattox-Buckingham State Forest in the Piedmont of Virginia. The purpose of the RW-19 trials is to examine the interaction of stand density (manipulated through mid-rotation thinning) and fertilization. Plots have been established using a split-plot design and thinning treatments were completed in early 2009. Fertilization of whole plots occurred in March, 2009. Annual measurements are being collected. A Seond thinning on some plots is scheduled for early spring 2018.

Regionwide Thinning Study
This thinning study consists of permanent plots established at 186 locations throughout the native range of loblolly pine. At each location, three comparable plots were established. Each plot was randomly assigned to a treatment category: (1) "control," (2) "light thin," or (3) "heavy thin". All planted pines, plus volunteer pines and hardwoods in the main canopy, were tagged and all plots were stem mapped. These plots were established in 1980-82 and have been remeasured at three-year intervals since installation. At the fourth remeasurement, second thinnings were imposed on certain plots and stem quality and wood sample data were collected from selected trees. Final live tree measurements, 21 years after installation, have been collected. Additional data from dead trees and wood samples from remaining live trees were collected at the termination of the study, which occurred in 2004. These data are still being used to evaluate and test growth and yield relationships.

Spacing Trials
During 1983-1984 the Cooperative installed a set of designed spacing trials. The purpose of these spacing experiments is to provide reliable information on optimal density for given product objectives, juvenile growth and mortality relationships and density effects on diameter and height growth. Three replications were established at each of four locations. The sites are in the piedmont and coastal plain regions of North Carolina and Virginia. Frequent measurements of height, diameter and crown dimensions have been collected. Results from these trials have proven valuable in structuring and formulating growth and yield models.After 25 years of growth measurements, a lumber recovery study was completed from sample trees felled on the two coastal plain sites. Ninety-eight sample trees from the 6ft x 6ft, 8ft x 8ft and 12ft x 12ft spacings were felled and sawn into boards of 2-by and 1-by material. All 2-by boards were graded by a certified grader and were dried. Following drying, sample boards were tested for specific gravity, MOE and MOR. The milling study data were used to relate the quantity and quality of sawn lumber to the spacing treatments.