Nitrogen inputs by biological soil crusts in grasslands of interior British Columbia.

The relationship between climate and inputs of nitrogen and carbon by biological soil crusts (BSCs) was examined in British Columbia’s Chilcotin and Thompson River grasslands. Variation in nitrogen and carbon of BSCs and associated soils was examined in relation to gradients in temperature and moisture availability. Patterns of N-fixation activity by BSCs were also examined in relation to climate, and used to model N- fixation rates throughout the year. BSCs were found to significantly contribute to soil carbon and nitrogen, particularly in the labile N fraction. Two peak periods were observed for N-fixation – one during the spring snowmelt, and one during midsummer rainy periods. N-inputs appeared to be sensitive to changes in precipitation patterns. Annual estimates of N-inputs for BSCs in this ecosystem could be as high as 83 kg N ha⁻¹ but the fate of this N (i.e. plant uptake, denitrification or volatization) is still unknown.