Elevated CO2 effects on carbon and nitrogen cycling in grass/clover turves of a Psammaquent soil

摘要: Effects of elevated CO2 (525 and 700 μL L−1), a control (350 L−1 CO2), on biochemical properties Mollic Psammaquent soil in well-established pasture C3 C4 grasses clover were investigated with continuously moist turves growth chambers over four consecutive seasonal temperature regimes from spring to winter inclusive. After further ‘spring’ period, half the under 350 subjected ‘summer’ drying then re-wetted before ‘autumn’ period; remaining kept throughout these additional three ‘seasons’. The pulse-labelled 14C-CO2 follow C pathways plant/soil system during 35 days. Growth rates herbage first ‘seasons’ averaged 4.6 g m−2 day−1 about 10% higher than other two treatments. Below-ground net productivity at end 465, 800 824 control, 525 treatments, respectively. soil, had no overall effects total, extractable or microbial N, invertase activity, but resulted increased CO2-C production added initial stages decomposition 21 days; root unaffected. produced h−1 mg−1 was treatment Elevated clearly defined N availability, mineralization herbage. In labelling experiment, relatively more 14C occurred below ground CO2, enhanced turnover also being suggested. Drying levels organic-N, decreased mineral-N concentrations; it effect C, lowered only. that been previously ‘summer’-dried, again higher, lower, after growth. Over trial period 422 days, generally appears have greater pools this ecosystem.