Short-term effects of nitrogen deposition on soil microbial biomass in Calluna heathlands NW Spain: critical loads

Javier Calvo-Fernández, Elena Marcos, Leonor Calvo



We evaluate the short-term effects of different N deposition loads on nutrient dynamic of soil microbial biomass in Cantabrian heathlands. A surplus of 10 kg N ha-1 yr-1 above N background deposition was required to increase soil microbial biomass N content in old Calluna heathlands, while a surplus of 20 kg N ha-1 yr-1 was required in young ones. The increase of atmospheric N deposition showed no change in soil microbial biomass C content. This caused a decrease in C:N ratio with the highest N deposition loads, being linked to a bacterial biomass dominance against fungal dominance.


Calluna vulgaris; Cantabrian heathlands; N critical loads; soil microbial biomass; C:N ratio

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