1. CROP TREE GROWTH AND QUALITY TWENTY- FIVE YEARS AFTER PRECOMMERCIAL THINNING IN A NORTHERN CONIFER STAND Leah M. Phillips 1, Robert S. Seymour 1, and Laura S. Kenefic 2 1 Department of Forest Ecosystem Science, 5755 Nutting Hall, University of Maine, Orono, ME 04469 2 USDA Forest Service, Northeast Research Station, 686 Government Rd., Bradley, ME 04411 EXPERIMENTAL DESIGN: Nine 19.5 x 19.5 m measurement plots were utilized for this study; four 2.4 x 2.4 m PCT plots and five unspaced plots. The crop tree sample consisted of: 20 balsam fir & 17 red spruce in the unspaced plots; and 20 balsam fir & 23 red spruce in the spaced plots, for a total of 80 crop trees. DATA COLLECTION: Crop trees were climbed using ladders for stem form measurements up the tree bole. Diameter measurements included: DBH, diameter 1.0 m below bh, and diameter at 1.0 m intervals up to the live crown base. Other measurements included: THT, height to the lowest live branch (LLB) & lowest live whorl (LLW); and branch diameters between 1.0 - 2.0 m above bh and between LLB & LLW. KEY OBJECTIVES: Compare crop tree growth and productivity between species and treatments as determined by growth efficiency (GE); Compare stem form of crop trees between species and treatments; and determine the extent of branchiness and its effect on wood quality. RESULTS: Conclusions: Treatment: projected leaf area (PLA), crown projection area (CPA), total tree volume, stem taper, knot volume, and the # and size of branches differed between treatments. Growth efficiency (GE) & tree-level LAI were not affected by treatment. Species: GE, CPA, total tree volume, tree-level LAI, and knot volume differed between species. PLA, stem taper, and the # and size of branches did not differ. Fig. 1.1 Growth efficiency (GE dm 3 /m 2 ) in relation to projected leaf area (PLA m 2 ) for balsam fir crop trees. 020406080 Projected leaf area (m 2 ) 0.05 0.10 0.15 0.20 0.25 0.30 Growth efficiency (dm 3 /m 2 ) Unspaced Spaced Treatment GE = b 0 +b 1 *(PLA) Fig. 1.2 Growth efficiency (GE dm 3 /m 2 ) in relation to projected leaf area (PLA m 2 ) for red spruce crop trees. 020406080 Projected leaf area (m 2 ) 0.05 0.10 0.15 0.20 0.25 0.30 Growth efficiency (dm 3 /m 2 ) Unspaced Spaced Treatment Fig. 1.3 Growth efficiency (GE dm 3 /m 2 ) in relation to crown projection area (CPA m 2 ) for balsam fir crop trees. 0102030 Crown Projection Area (m 2 ) 0.0 0.5 1.0 1.5 2.0 Growth Efficiency (dm 3 /m 2 ) Unspaced Spaced Treatment Fig. 1.4 Growth efficiency (GE dm 3 /m 2 ) in relation to crown projection area (CPA m 2 ) for red spruce crop trees. 0102030 Crown Projection Area (m 2 ) 0.0 0.5 1.0 1.5 2.0 Growth Efficiency (dm 3 /m 2 ) Unspaced Spaced Treatment GE = b 0 +b 1 *(PLA) GECPA = b 0 +b 1 *(CPA) Fig. 1.5 Total tree volume (m 3 ) in relation to diameter at breast height (DBH cm) for balsam fir crop trees. 510152025 Diameter at breast height (cm) 0.00 0.06 0.12 0.18 0.24 0.30 Tree Volume (m 3 ) Unspaced Spaced Treatment Fig. 1.6 Total tree volume (m 3 ) in relation to diameter at breast height (DBH cm) for red spruce crop trees. 510152025 Diameter at Breast Height (cm) 0.00 0.06 0.12 0.18 0.24 0.30 Tree Volume (m 3 ) Unspaced Spaced Treatment Tree volume = b 0 +b 1 *(DBH) STUDY AREA: The Penobscot Experimental Forest (PEF) is located in Bradley, Maine. The study reported here is part of an ongoing precommercial thinning (PCT) study (STUDY 58) established in 1976 by the USDA Forest Service. The stand was regenerated by a two-stage shelterwood method; where 46% of the overstory was removed in the establishment harvest in 1957, and the remaining overstory was removed in 1967.