Soil Carbon and Nitrogen Dynamics Followed by a Forest-to-pasture Conversion in Western Mexico

Abstract

Gains and losses of soil carbon (C), have been reported when tropical forests are converted to pastures. Regional studies are crucial for setting regional baselines and explaining each particular trend, in order to solve this controversy. Tropical deciduous forest (TDF) is under high deforestation pressure, mainly for conversion to pastures. The present study compared soil organic C (SOC) and nitrogen (SON) in the surface layer (0-5 cm) of forest and pasture soils in a TDF of western Mexico. SOC and SON concentrations were 18 and 60% lower in pasture soils than in forest soils, and C:N ratio increased in pasture soils. Furthermore, pasture soils had lower labile C and available inorganic nitrogen (N) than forest soils. These results can be explained as a reduction in C inputs to pasture soils and management-induced disruption of soil aggregates. In forest soils, macroaggregates (>250 lm) were predominant (85%), whereas in pasture soils they were reduced to 35% of dry sand-free soil mass. The estimated SOC and SON losses from the top 5 cm of soil were 3 Mg C ha À1 and 0.9 Mg N ha À1 , respectively.

Soil carbon stocks and changes after oil palm introduction in the Brazilian Amazon

“…The pasture system showed the highest carbon stocks, as has been observed in numerous other studies in the Amazon region (Fearnside & Barbosa, 1998;Cerri et al, 2003;Zinn et al, 2005;Garcia-Oliva et al, 2006). Increased soil C concentrations in surface horizons are a common consequence of pasture formation after forest has been cleared in the Amazon basin (Bonde et al, 1992;Moraes et al, 1995Moraes et al, , 1996Trumbore et al, 1995;Neill et al, 1997;Bernoux et al, 1998).…”

Dissolved organic carbon affects soil microbial activity and nitrogen dynamics in a Mexican tropical deciduous forest

“…This could increase N loss by nitrate leaching as well as by emissions of N oxides (Paul and Clark 1989;Davidson and Kingerlee 1997). N losses through nitrification could be magnified when soil C levels decrease due to forest conversion (García-Oliva et al 2006). Our results highlight the need to consider functionally coupled C and N dynamics in tropical deciduous forest soils.…”

Restoration of dry tropical forests in Central America: A review of pattern and process

“…Total soil nitrogen can decline by 23-60% (Johnson and Wedin, 1997;Ellingson et al, 2000;Garcia-Oliva et al, 2006;Sandoval-Perez et al, 2009) while soil carbon can decline 18-47% in dry regions of Central America (Johnson and Wedin, 1997;Garcia-Oliva et al, 2006;Sandoval-Perez et al, 2009). The conversion of forest to pasture, grazed for more than 20 years resulted in a loss of 10 Mg ha −1 C in moist forest ecosystems of Panama (Neumann-Cosel et al, this issue).…”