Measurements of respiration and microbial assimilation of carbon substrates and priming of soil organic matter mineralisation in tropical lowland and montane forest soils

Soils were sampled in January 2012 from ten sites along a tropical elevation gradient located on the east flank of the Peruvian Andes, with site elevations ranging from 210 to 3400 metres (m) above sea-level (asl). All sites have continuous forest cover ranging from lowland Amazonian rainforest to upper montane cloud forest; the tree-line is situated at approximately 3500 m asl. Annual temperature decreases with increasing elevation along this transect, from 26-8 degrees Centigrade (oC). Annual precipitation ranges from 1700 to 3200 millemetres per year (mm yr-1). Soil water content has been reported to have no clear relationship with elevation, partly due to limited evapotranspiration and fog deposition within the cloud immersion zone (1500-3400 m asl). At each site, the organic layer was sampled from 5 sub-plots within established 1 hectare (ha) plots with the organic layer removed from a 40 x 40 centimetre (cm) area in each sub-plot. Soils were sealed in plastic bags, immediately transported to the laboratory, and stored at 4 oC for 6 weeks until used for experimentation and analysis.