Carbon and nutrient stocks in roots of forests at different altitudes in the Ecuadorian Andes

Carbon and nutrient stocks in below-ground biomass have rarely been investigated in tropical montane forests. Inthepresentstudy, theamountsofcarbon,nitrogen,phosphorus, sulphur,potassium,calciumandmagnesium in root biomass were determined by soil coring and nutrient analysis in forests at three altitudes (1900, 2400 and 3000m) in the Ecuadorian Andes. Root biomass increased markedly from 2.8 kg m−2 at 1900m and 4.0 kg m−2 at 2400 to 6.8 kg m−2 at 3000m. The contribution of coarse roots (> 2mm in diameter) to total root biomass increased from about 70% at 1900m to about 80% at higher altitudes. In fine roots (≤ 2mm in diameter), concentrations of nutrients except calcium markedly decreased with altitude. Therefore, the nutrient stocks in fine roots were similar at 1900m and 3000m for nitrogen and sulphur, and were even lower at higher altitudes for phosphorus, potassium and magnesium. In coarse roots of Graffenrieda emarginata concentrations of nutrients were substantially lower than in fine roots, and were little affected by altitude. The data suggest that the importance of coarse roots for long-term carbon and nutrient accumulation in total plant biomass increases with increasing altitude.