Below-ground responses of loblolly pine and sweetgum in pure and mixed culture to CO[sub 2] enrichment, water and nutrient status

• Published in: Bulletin of the Ecological Society of America; (United States) Vol. 74:2
• Main Authors: Jifon, J.L., Friend, A.L., Berrang, P., Seiler, J.R., Zedaker, S.M.
• Format: Conference Proceeding
• Language: English
• Published: United States 01-06-1993
• Subjects: BIOLOGICAL EFFECTS; CARBON COMPOUNDS; CARBON DIOXIDE; CARBON OXIDES; CHALCOGENIDES; CONIFERS; ELEMENTS; GROWTH; HYDROGEN COMPOUNDS; MAGNOLIOPHYTA; MAGNOLIOPSIDA; NITROGEN; NONMETALS; NUTRIENTS; OXIDES; OXYGEN COMPOUNDS; PINES; PINOPHYTA; PLANTS; RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT; ROOTS; SEEDLINGS; SWEET GUMS; TREES 560300 > Chemicals Metabolism & Toxicology; WATER
• ISSN: 0012-9623; 2327-6096

To determine how below-ground processes are affected by CO[sub 2] under varied water and nutrient (nitrogen, N) regimes, loblolly pine and sweetgum seedlings were exposed to 350 ppm CO[sub 2] or 700 ppm CO[sub 2] in continuously-stirred tank reactors. Miniature stands (2.5 x 2.5 cm spacing) were raised in forest soil in 22-L pots for two accelerted growth cycles (42 wks. total). Three stand-types were raised: pine in monoculture, sweetgum in monoculture, and 50:50 mixtures of pine-sweetgum. Root growth responses (determined for 87 cm[sup 3] soil cores), differed according to stand type; sweetgum stands were more responsive to treatments than pine stands, and mixed stands of sweetgum were even more responsive than monocultures. At the end of the second growth cycle, root growth was generally increased by CO[sub 2]-enrichment (1.2 to 1.7-fold increase). Water and nitrogen effects were strong but varied in direction (increased or decreased root growth) according to stand type. Interactions of particular interest were those involving the influence of water and/or N on CO[sub 2] responses. The positive effect of CO[sub 2]-enrichment on root growth were consistently greater under water- or N-limited conditions for all stand types, and this pattern was most evident for sweetgum in mixture. For example, under water stress, CO[sub 2]-enrichment increased root length density (cm root/cm[sup 3] soil) of sweetgum by 74% and that of pine by 34%, whereas under high water, the increase was 32% for sweetgum and 10% for pine. This suggests an increased capacity of sweetgum to exploit a given soil volume, under elevated atmospheric CO[sub 2], as compared with pine.