Carbon sequestration as influenced by diverse riparian buffer systems in Southern Ontario, Canada

Abstract

Agriculture and forestry related land modifications are globally blamed for a quarter of the accumulated atmospheric greenhouse gasses (GHGs). Riparian buffer systems (RBSs) comprised of perennial vegetations are established between adjacent land-use and aquatic ecosystems to control non-point source pollutants entering water sources from adjacent urban, industrial, or agricultural land-use. RBSs can sequester atmospheric carbon dioxide (CO2) into stable carbon (C) pools. C sequestration potential of diverse RBSs [tree buffers (coniferous and deciduous, rehabilitated, natural forest buffers) and grass buffers] are however, less documented. The soil organic C (SOC) contained in soils (0 – 60cm) and riparian biomass C were quantified in various RBSs. Tree buffers showed significantly higher (p < 0.05) SOC sequestration potential (334.10 Mg C ha-1) than grass buffers (121.11 Mg C ha-1). Annual rate of SOC sequestration was significantly higher (p < 0.05) in rehabilitated buffers (4.71 Mg C ha-1y-1) than in natural forest buffers (3.14 Mg C ha-1y-1). The results emphasize the potential of RBSs as best management practice for enhancing soil C sequestration in agricultural ecosystems. Natural forest buffers showed significantly higher (p < 0.05) system-level C sequestration potential (SLCSP) (806.69 Mg C ha-1) than rehabilitated buffers (460.31 Mg C ha-1). Annual SLCSP was, however, significantly higher (p < 0.05) in rehabilitated buffers (11.23 Mg C ha-1y-1) than natural forest buffers (5.17 Mg C ha-1y-1). This suggests that maintaining younger RBSs with fast growing tree species should be encouraged in the province of Ontario and across Canada. SOC associated with large macroaggregates ((LM), > 2 mm), small macroaggregates (SM, (250 – 2000 µm)), free microaggregates (free micro, (53 µm – 250 µm)), free silt and clay (free s+c), < 53 µm)) were quantified. The free micro-C stocks (0 – 30 cm) was significantly higher (p < 0.05) in tree (30.48 Mg C ha-1) than grass buffers (19.70 Mg C ha-1), and the free s+c-C (30 – 60 cm) was significantly lower (p < 0.05) in rehabilitated buffers (8.11 Mg C ha-1) than in natural forest buffers (24.76 Mg C ha-1), showing superior potential of mature tree buffers to store stable soil C pools than grass buffers.