Elevated Ozone Negatively Affects the Community Characteristics and Productivity of Subtropical Grassland in India

Tropospheric ozone (O 3 ) is found to be a severe threat to agriculture and natural vegetation. The present study was conducted to investigate the structural and functional changes in an intact seminatural grassland community when exposed to elevated O 3 (EO 3 ; ambient + 20 parts per billion) compared to ambient O 3 (AO 3 ) for 3 years using open-top chambers. Parameters such as species richness (SR), evenness ( E ), Shannon index ( H ′), β-diversity (BD), concentration of dominance (Cd), similarity index (SI), biomass in canopy layers, and community productivity were evaluated. Species like Cynodon dactylon , Dichanthium annulatum , Parthenium hysterophorus , Digitaria sanguinalis , Cyperus killinga , Oplismenus burmannii , and Commelina benghalensis showed higher importance value index (IVI), whereas Trifolium resupinatum , Desmodium triflorum , Melilotus officinalis , Oxalis corniculata , Eleusine indica , Cyperus rotundus , Malvestrum coromandelianum , and Lindernia anagallis showed lower IVI under EO 3 treatment compared to AO 3 . EO 3 enhanced BD and Cd, whereas SR, E , and H ′ in the community reduced. Biomass accumulation reduced maximally in top layer compared to bottom and middle canopy layers in both forbs and grasses fraction under EO 3 treatment. Higher reduction in total biomass compared to aboveground biomass indicates less carbon allocation toward root system. The results of the present study clearly indicates that 3 years of exposure at EO 3 level caused deleterious impact on grassland community by increasing O 3 -tolerant and decreasing sensitive species, thus resulting in a shift in species composition and community productivity.