Long-term trends in loblolly pine productivity and stand characteristics in response to thinning and fertilization in the West Gulf region |
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| Institution: | 1. USDA Forest Service, Southern Research Station, Alexandria Forestry Center, 2500 Shreveport Highway, Pineville, LA 71360, USA;2. School of Renewable Natural Resources, LSU AgCenter, Baton Rouge, LA 70803, USA;1. The Jones Center at Ichauway, 3988 Jones Center Drive, Newton, GA 39870, United States;2. Clemson University, Belle W. Baruch Institute of Coastal Ecology and Forest Science, Department of Forestry and Environmental Conservation, P.O. Box 596, Georgetown, SC 29442, United States;3. Clemson University, Department of Forestry and Environmental Conservation, 261 Lehotsky Hall Box 340317, Clemson, SC 29634, United States;1. Department of Natural Resources and Environmental Management, Oklahoma State University, Stillwater, OK 74078, United States;2. Kiamichi Forestry Research Station, Oklahoma State University, Idabel, OK 74745, United States;3. Tree-Ring Laboratory, Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States;4. Southern Research Station, USDA—Forest Service, Hot Springs, AR 72701, United States;1. Southern Research Station, USDA Forest Service, 521 Devall Drive, Auburn, AL 36849, USA;2. The Nature Conservancy, 4245 Fairfax Dr #100, Arlington, VA 22203, USA;3. College of Forestry, Wildlife, and Environment, Auburn University, 602 Duncan Dr., Auburn, AL 36849, USA;4. Department of Forestry, Mississippi State University, 775 Stone Blvd, MS 39762, USA;1. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA;2. Center for Forest Disturbance Science, USDA Forest Service, 320 Green Street, Athens, GA 30602, USA;3. Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA |
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| Abstract: | Two levels each of thinning and fertilization were applied to a 7-year-old loblolly pine (Pinus taeda L.) plantation on a nitrogen- and phosphorus-deficient West Gulf Coastal Plain site in Louisiana. Levels of thinning were no thinning, or thinning applied 7 and 14 years after stand initiation. Levels of fertilization were no fertilization or broadcast fertilization with diammonium phosphate at age 7 years plus refertilization with urea, monocalcium phosphate, and potash at age 14 years. Long-term measurements of climate, stand development and productivity, projected leaf area index, and foliar nutrition were initiated at age 11 years. We found that by age 17 years, thinning increased mean live-crown length from 4.2 to 7.8 m, and mean tree diameter from 15.0 to 21.8 cm compared to the unthinned treatment. After rethinning at age 14 years, stand basal area increased 1.2 and 19.2% between ages 15 and 17 years on the unthinned and thinned plots, respectively. Refertilization at age 14 years reestablished foliar N, P and K sufficiency, which increased leaf area index from 4.2 to 6.0 m2 m?2 on the unthinned plots and from 3.2 to 3.8 m2 m?2 on the thinned plots, and subsequently, increased gross stand biomass from 114 to 141 Mg ha?1 on the unthinned plots and from 78 to 95 Mg ha?1 on the thinned plots by age 17 years. Leaf area was an important factor controlling loblolly pine productivity. At our study site, however, competition for light and water and nutrition-limited foliage growth influenced the variability and scope of this relationship. Our results suggest that a positive and linear relationship between leaf area and loblolly pine productivity does not universally occur on loblolly pine sites. |
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