Free-Air CO2 Enrichment (FACE) and Free-Air Temperature Increase (FATI) Effects on Trifolium repens L. in Temperate Himalayas

Abstract

Changes in phenology, growth, biomass production and photosynthetic parameters in Trifolium repens L. were studied under Free Air CO2 Enrichment (FACE; 550 ± 50 µmol mol−1 [CO2]) and Free Air Temperature Increment FATI for 2 years during 2010–11 and 2011–12 in temperate Himalaya. Plant height, root volume, leaf area and dry biomass of T. repens increased from 8.8 to 33.5% under elevated [CO2] but decreased from 4.6 to 58.1% under elevated temperature compared to ambient environment. Leaf area increased by 24.1 and 29.5% under elevated [CO2], however, elevated temperature reduced leaf area by 78.1 and 38.6% compared to ambient conditions during 2010–11 and 2011–12, respectively. Leaf net photosynthetic rates (PN) and stomatal conductance (gS) measured at 390 ± 10 µmol m−2 s−1 CO2, declined under FACE and FATI environment as compared to control conditions, with greater reduction during year 2011–12 than 2010–11. The values of PN in year 2011–2012 during spring and autumn were lower by 13% and 7% under FACE and 24% and 18% under FATI, respectively, compared to ambient (control) conditions, when measured at 400 µmol m−2 s−1. For year 2012, gS showed a decrease by 26% and 39% under FACE and by 21% under FATI during spring and autumn months, respectively, compared to ambient conditions. All phenological stages were significantly advanced under elevated temperature but showed a delayed response under elevated [CO2] as compared to ambient conditions.