Soil-nutrient availability modifies the response of young pioneer and late successional trees to elevated carbon dioxide in a Brazilian tropical environment

Author(s)

Dias de Oliveira, Eduardo Augusto ^[1] ; Approbato, Andressa Uehara ^[1] ; Legracie, Jr., Jose Renato ^[1] ; Martinez, Carlos Alberto ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Biol, FFCLRP, BR-14040901 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: ENVIRONMENTAL AND EXPERIMENTAL BOTANY; v. 77, p. 53-62, APR 2012.
• Web of Science Citations: 15

Abstract

The aim of this work was to determine the impact of three levels of {[}CO2] and two levels of soil-nutrient availability on the growth and physiological responses of two tropical tree species differing in their ecological group: Croton urucurana Baillon, a pioneer (P), and also Cariniana legalis (Martius) Kuntze, a late succession (LS). We aimed to test the hypothesis that P species have stronger response to elevated {[}CO2] than LS species as a result of differences in photosynthetic capacity and growth kinetics between both functional groups. Seedlings of both species were grown in open-top-chambers under high (HN) or low (LN) soil-nutrient supply and exposed to ambient (380 mu mol mol(-1)) or elevated (570 and 760 mu mol mol(-1)) {[}CO2]. Measurements of gas exchange, chlorophyll a fluorescence, seedling biomass and allocation were made after 70 days of treatment. Results suggest that elevated {[}CO2] significantly enhances the photosynthetic rates (A) and biomass production in the seedlings of both species, but that soil-nutrient supply has the potential to modify the response of young tropical trees to elevated {[}CO2]. In relation to plants grown in ambient {[}CO2], the P species grown under 760 mu mol mol(-1) {[}CO2] showed increases of 28% and 91% in A when grown in LN and HN, respectively. In P species grown under 570 mu mol mol(-1) {[}CO2], A increased by 16% under HN, but there was no effect in LN. In LS species, the enhancement of A by effect of 760 mu mol mol(-1) {[}CO2] was 30% and 70% in LN and HN, respectively. The exposure to 570 mu mol mol(-1) {[}CO2] stimulated A by 31% in HN, but was no effect in LN. Reductions in stomatal conductance (g(s)) and transpiration (E), as a result of elevated {[}CO2] were observed. Increasing the nutrient supply from low to high increased both the maximum rate of carboxylation (V-cmax) and maximum potential rate of electron transport (J(max)). As the level of {[}CO2] increased, both the V-cmax and the J(max) were found to decrease, whereas the J(max)/V-cmax ratio increased. In the LS species, the maximum efficiency of PSII (F-v/F-m) was higher in the 760 mu mol mol(-1) {[}CO2] treatment relative to other {[}CO2] treatments. The results suggest that when grown under HN and the highest {[}CO2], the performance of the P species C. urucurana, in terms of photosynthesis and biomass enhancement, is better than the LS species C. legalis. However, a larger biomass is allocated to roots when C. legalis seedlings were exposed to elevated {[}CO2]. This response would be an important strategy for plant survival and productivity of the LS species under drought stresses conditions on tropical environments in a global-change scenario. (C) 2011 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 05/54804-7 - Impact of raised concentrations of CO2 on the physiology and the initial growth of four Brazilian forest species, in a future climatic simulation
• Grantee: Carlos Alberto Martinez y Huaman
• Support Opportunities: Regular Research Grants