Effects of elevated CO2 and N deposition on plant biomass accumulation and allocation in subtropical forest ecosystems: a mesocosm study.

Abstract

Aims Interactive effects of elevated atmospheric CO2 concentration (CO2) and nitrogen (N) deposition on terrestrial ecosystems play an important role in global carbon cycling. Ecosystems in subtropical and tropical areas occupy a large percent of the global biomass, but few studies have been done in these areas. Therefore, our objective was to conduct an experiment to improve our understand- ing of atmospheric (CO2) enrichment and N deposition effects on biomass accumulation and allocation in subtropical and tropical forests. Methods A model forest ecosystem was constructed of five tree species native to South China: Schima superba, Castanopsis hystrix, Ormosia pinnata, Acmena acuminatissima and Syzygium hancei. The species were exposed to a factorial combination of elevated CO2 and high N deposition in open-top chambers beginning March 2005. There are four experimental treatments, including CN (elevated (CO2) of (700±20) μmol⋅mol -1 and high N of 100 kg N⋅hm -2 ⋅a -1 ), C+ (elevated (CO2) of (700±20) μmol⋅mol -1 and ambient N), N+ (ambient (CO2) and high N of 100 kg N⋅hm -2 ⋅a -1 ) and CK (ambient (CO2) and am-