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Title: Irrigation and fertilization effects on foliar and soil carbon and nitrogen isotope ratios in a loblolly pine stand
Author: Choi, Woo-Jung; Chang, Scott X.; Allen, H. Lee; Kelting, Daniel L.; Ro, Hee-Myong;
Source: Forest Ecology and Management 213: 90-101
Publication Series: Miscellaneous Publication
Description: We examined 813C and 815N in needle (current and 1-year-old) and soil samples collected on two occasions (July and September 1999) from a 15-year-old loblolly pine (Pinus taeda L.) stand in an irrigation and fertilization experiment to investigate whether these treatments leave specific isotope signals in the samples and thus to infer the effects of treatments on C and N cycling. Irrespective of foliar age or sampling date, carbon isotope discrimination (A) was increased by irrigation, and decreased by fertilization. The carbon isotope discrimination model suggested that increased A by irrigation was due to decreased water use efficiency (WUE) through increased stomatal and/or mesophyll conductance. The decreased A by fertilization and published gas exchange measurements at the same site suggest that water stress resulting from increased water demand in the fertilized plots improved WUE through increased stomatal control of water loss. Foliar 815N values were not affected by irrigation, but were increased by fertilization. The 815N value of soil NH4 were higher than those of NO3 and were positively correlated with foliar 815N, suggesting that tree uptake of NH4* was one of the factors affecting foliar 815N. We conclude that irrigation and fertilization affected 813C and 815N values in plant and soil samples, reflecting changed C and N cycling patterns and water use efficiency in the studied loblolly pine stand.
Keywords: 13C/12C, 15N/14N, carbon isotope discrimination, nitrification, water use efficiency, Pinus taeda
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Choi, Woo-Jung; Chang, Scott X.; Allen, H. Lee; Kelting, Daniel L.; Ro, Hee-Myong 2005. Irrigation and fertilization effects on foliar and soil carbon and nitrogen isotope ratios in a loblolly pine stand. Forest Ecology and Management 213: 90-101
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