Response of a tropical N[sub 2]-fixing tree (Gliricidia sepium (Jacq. )Walp. ) to increased atmospheric CO[sub 2] and air temperature

Gliricidia sepium, a tropical leguminous tree species, was grown from seed for 100 days at two CO[sub 2] partial pressures (35 and 70 Pa) and two air temperatures (28/24 C and 32/28 C, day/night). Seedlings were grown with and without N fertilizer (0, 1 and 10 mM) to facilitate a stable isotope tech...

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Bibliographic Details
Main Authors: Thomas, R.B., Bashkin, M.A., Richter, D.D.
Format: Conference Proceeding
Language:English
Subjects:
AMBIENT TEMPERATURE
BIOLOGICAL EFFECTS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
ECOLOGICAL CONCENTRATION
GROWTH
LEGUMINOSAE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
OXIDES
OXYGEN COMPOUNDS
PLANT GROWTH
PLANTS 560300 > Chemicals Metabolism & Toxicology
RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT
TREES
TROPICAL REGIONS
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Summary:Gliricidia sepium, a tropical leguminous tree species, was grown from seed for 100 days at two CO[sub 2] partial pressures (35 and 70 Pa) and two air temperatures (28/24 C and 32/28 C, day/night). Seedlings were grown with and without N fertilizer (0, 1 and 10 mM) to facilitate a stable isotope technique to analyze N[sub 2]-fixation. We hypothesized that elevated CO[sub 2] would reduce stress imposed by elevated air temperature. Elevated CO[sub 2] enhanced nitrogen fixation across all treatments by increasing module mass (59%) and N[sub 2]-fixation rate on a nodule mass basis (24%). Elevated CO[sub 2] increased seedling mass (60%, 111%), nodule mass (40%, 78%) and N[sub 2]-fixation rate (17%, 33%) in the low and high temperature treatments, respectively. In 35 Pa CO[sub 2], the 4 degree increase in air temperature reduced N[sub 2]-fixation rate by 15%, but seedling content was unaffected because N absorption rate by roots was stimulated by 32%. In 70 Pa Co[sub 2], small reductions in N[sub 2]-fixation rate (3%) and N absorption rate (8%) due to increased temperature were compensated by the stimulation of root mass (28%) and nodule mass (29%). Nitrogen fertilizer inhibited nodulation, but N[sub 2]-fixation rate on a nodule basis as unaffected. Negative effects of N fertilizer on N[sub 2]-fixation were ameliorated by elevated CO[sub 2] suggesting that increased carbon availability partially negates inhibitory effects of soil N. As CO[sub 2] increases, N contributions to tropical ecosystems by symbiotic N[sub 2]-fixing trees may increase, and the duration of N[sub 2]-fixing trees in early successional forests may be lengthened.
ISSN:0012-9623
2327-6096