Response of soil surface CO2–C flux to land use changes in a tropical cloud forest (Mexico)

It is well known that land use changes contribute to increased atmospheric CO2 concentrations. In the middle segment of the eastern slope of the Cofre de Perote Volcano (Mexico), many areas of tropical cloud forest have been converted to grassland and corn cropland. I investigated the response of soil surface CO2–C flux to land use change over a 1.2-year period (May 2003–June 2004). To do this, soil surface CO2–C flux was measured monthly in a tropical cloud forest, a corn–potato–corn rotation plot and a grassland using the static chamber method. Average CO2 flux varied from 0.54 to 2.21 g C m−2 day−1 in the tropical cloud forest, 0.43 to 3.07 g C m−2 day−1 in the corn–potato–corn rotation and 1.51 to 4.87 g C m−2 day−1 in the grassland. Soil surface CO2–C flux increased significantly with the change from tropical cloud forest to managed ecosystems. The highest CO2 flux occurred in summer, with peaks in September 2003 for tropical cloud forest and grassland sites and in July 2003 and May 2004 for corn–potato–corn rotation. In autumn, soil surface CO2–C flux started to decrease, with the lowest flux occurring in winter. For the entire data set, there was a weak positive correlation between soil surface CO2–C flux and soil temperature (R2 = 0.12, P < 0.0001) and a weak negative correlation between soil surface CO2–C flux and air-filled pore space (R2 = 0.17, P < 0.0001). The results indicate that tropical cloud forest, corn–potato–corn rotation, and grassland growing under the same climatic and soil conditions have different soil surface CO2–C flux rates.