Growth pattern of Picea rubens prior to canopy recruitment |
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Authors: | Wu Xinyuan McCormick J Frank Busing Richard T |
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Institution: | (1) Management Texas A&M University, College Station, TX 77843, USA;(2) Department of Ecology and Evolutionary Biology, The University of Tennessee, Knoxville, TN 37996, USA;(3) Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331, USA |
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Abstract: | A majority (72%) of Picea rubens Sarg. (red spruce) trees in an old-growth spruce-fir forest in the Great Smoky Mountains underwent episodes of radial growth suppression and release before they reached the forest canopy. Prior to canopy recruitment, trees experienced an average of 1.43 and a maximum of 7 suppression periods with an average ring width of 0.257 mm. Duration of suppression periods ranged from 4 to 79 years with an average of 19.05 years, which was significantly shorter than the average duration of release periods (29.00 years). Mean ring width in a suppression period was negatively correlated with duration of the suppression period. The opposite was true for release periods. The severity of suppression had no significant effect on mean ring width in subsequent release periods. Greater suppression was observed in the recent growth pattern of current non-canopy trees than in the historical growth pattern reconstructed from current canopy trees. Growth releases prior to canopy recruitment, triggered by small gaps or neighboring gaps, displayed a continuous pattern over the last two centuries and had consistent frequency in recent decades. By contrast, canopy recruitment resulting from large-gap disturbances was discontinuous over the last two centuries, and less frequent after 1850. |
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Keywords: | Canopy disturbance regime Great Smoky Mountains Radial growth Red spruce Suppression and release |
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