Large Effects of Land Use Conversion on C Storage in Dry Forest Ecosystems from Southern South America.

Net CO₂ land use change emissions represent one of the main drivers of global climatic change. However, the effect of the accelerated deforestation over plant and soil carbon (C) pools from dry Chaco forests from southern South America has been poorly quantified. Including five ecosystem types related to different land uses, we quantified the magnitude and change of total C stocks (including trees, shrubs, herbs, coarse and fine debris, soil organic and inorganic C stocks up to 2 m depth). C stocks in soils represented the largest C stocks in these forest ecosystems (more than 74%), and specifically C stored at deeper layers. Shrubs also comprises a large C stocks not quantified before in detail. The conversion of primary and secondary forest to degraded shrublands and croplands did generate high losses of organic C both in aboveground biomass and in soils up to 30 cm depth with values of c. 45.6 % of C loss. Although deeper soil C is in general stable, land use conversion did also imply changes in soil inorganic C (27.63 Mg C ha^-1 of net C loss). Our results indicate that a landscape transformation as the one predicted in the region may lead to a huge reduction of the C stored in these forest, with a consequent net C emission and a reduction in the associated ecosystem services provided to local, regional and global scales by dry Chaco forests.