Carbon stocks in a tropical pasture of México
Currently the carbon cycle and global warming are vital issues for the balance of the world’s environment, where the carbon stored in plant ecosystems plays a key role. It is a fact that the forest ecosystems have the largest carbon stocks of plant ecosystems, however grasslands that store less carbon per unit area, may also represent an important global reserve due to its larger area. Also, tropical ecosystems have been less studied than temperate ecosystems. The aim of this study was to estimate the carbon baseline of a typical pasture of tropical Mexico, in order to have another reference of carbon stocks in the tropical grasslands of the Americas. Two pastures of about 10 ha each, with the most common species of grasses in the area (Brachiaria decumbens and Paspalum notatum) were selected. In each pasture quadrats and sub-quadrats were randomly placed where the vegetation was allowed to grow and subsequently harvested to determine the total carbon content (TOC). The roots were harvested in trenches 1.0 m deep. The biomass was dried at 70 °C for three days, and the TOC was estimated by ignition at 400 °C. The values were extrapolated to tones per hectare.
A total of 39 species was found in the B. decumbens pasture and 42 species in the P. notatum pasture. Stored C was slightly higher in the roots than aboveground, being the largest stock in the top 40 cm of soil. Pastures of P. notatum stored 5.2 t C per ha in the root portion and 1.8 t C per ha aboveground, while B. decumbens stored 2.9 t C per ha in the root portion and 2.8 t C per ha in the aerial part. It can be concluded that in grasslands the root section is most important in the conservation of organic carbon, unlike forested ecosystems where the aerial part is usually the most important. Clearly C stocks in a tropical grassland, although it is smaller than in a wooded ecosystem it is so significant such that from the point of view of carbon sequestration, grasslands can represent important reserves worldwide because of its greater extent each year.