ASSESSMENT OF SOIL AND PLANT CARBON LEVELS IN TWO ECOSYSTEMS (WOODY BAMBOO AND PASTURE) IN MONTANE ECUADOR

Resumen

Although pasture maintains high soil carbon level, other better options may exist in the Neotropics, such as woody bamboo (Guadua angustifolia), in contributing to global C sequestration through increased soil carbon storage. A study was conducted in montane Ecuador to test a hypothesis that bamboo results in greater soil carbon levels than pasture ecosystems. We sampled soil at three depths (0-5, 5-15, and 15-30 cm) and measured standing biomass in six pasture-bamboo paired sites at elevations from 1000 to 1500 m a.s.l. in Nanegal, northwestern Ecuador. Compared with pasture, soils under bamboo at the above three depths had greater total C and N concentrations, and lower bulk densities. Because of the difference in soil bulk density between pasture and bamboo systems, C and N stock was calculated based on 30-cm soil depth in bamboo and corrected soil depth in pasture (22.6 cm) that provided soil mass equal to that under bamboo. The soil C stock at "equivalent 0-30" cm depth was greater under bamboo (60.8-123 Mg ha−1) than that under pasture (33.4-75.3 Mg ha−1). The carbon stock of bamboo standing biomass (51.8-95.6 Mg ha−1) was remarkably greater than that of pasture standing biomass (3.53-8.14 Mg ha−1). Higher soil N stock and lower C/N ratio were observed under bamboo than under pasture. Our results suggest that more C would be stored in terrestrial ecosystems with the planting of bamboo to degraded (pasture) soils in the Andes.