Soil Carbon and Nitrogen Dynamics Followed by a Forest-to-pasture Conversion in Western Mexico |
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Authors: | Felipe García-Oliva Juan F Gallardo Lancho Noé Manuel Montaño Pilar Islas |
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Institution: | 1. Centro de Investigaciones en Ecosistemas, UNAM, AP 27-3 Sta. María de Guido, 58090, Morelia, Michoacán, México 2. Consejo Superior de Investigaciones Científicas, I.R.N.A., Aptado. 257, 37071, Salamanca, Espa?a
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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 μm) 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−1 and 0.9 Mg N ha−1, respectively. |
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Keywords: | C:N ratio Land-use change Soil aggregates Tropical deciduous forest Tropical pastures |
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