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Title: Fine root dynamics in a developing Populus deltoides plantation
Author: Kern, Christel C.; Friend, Alexander L.; Johnson, Jane M.; Coleman, Mark D.
Publication: Tree Physiology. Volume 24, 2004. pp. 651-660.
Key Words: Cottonwood, fine root production, nitrogen fertilizer, root longevity, short rotation wood crops, stand development
Abstract: A closely spaced (1 x 1 m) cottonwood (Populus deltoides Bartr.) platation was established to evaluate the effects of nutrient availability on fine root dynamics. Slow-release fertilizer (17:6:12 N,P,K plus micronutrients) was applied to 225-m2 plots at 0, 50, 100, 200 kg N ha-1, and plots were monitored for two growing seasons. Fine root production, mortality, live root standing crop and life span were analyzed based on monthly minirhizotron observations. Fine root biomass was measured in soil cores. Fine root dynamics were controlled more by temporal, depth and root diameter factors than by fertilization. Cumulative fine root production and mortality showed strong seasonal patterns; production was greatest in the middle of the growing season and mortality was greatest after the grwoing season. Small diameter roots at shallow soil depths cycled more rapidly than large or deeper roots. The strongest trearment effects were found in the most rapidly cycling roots. The standing crop of live roots increased with fertilizer treatment according to both minirhizotron and soil coring methods. However, production and mortality had unique treatment response patterns. Although cumulative mortality decreasedd in response to increased fertilization, cumulative production was intermediate at 0 kg N ha-1, lowest with 50 kg N ha-1, and higest with 200 kg N ha-1. Above ground growth responded positively to fertilization up to an application rate of 50 kg N ha-1 but no further increase in application rate. Median fine root life span varied from 307 to over 700 day and increased with depth, diameter and nutrient availability.
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