The soils of the Mexican Volcanic Belt are part of ecosystems subjected to strong human impact du... more The soils of the Mexican Volcanic Belt are part of ecosystems subjected to strong human impact during the last six centuries. One measurable characteristic of the soil is the stable carbon isotopic relation of the soil organic matter (SOM) or d13C. The d13C SOM parameter is a genetic characteristic of soil reflecting the relative proportion of C3 and C4 that comes from colonizing plants having different photosynthetic C pathway and is used as a high-spatial resolution tool to infer paleoenvironmental changes.The d13C mean signatures of C3 and C4 plants are -27 and -13 %o, respectively. This work focuses on short-term changes in d13C on soils subjected to controlled agricultural practices during 2002-2005 in two sites of Mexico with similar annual precipitation and temperature. The tepetate was broken up 20y ago and ameliorated with fertilizers and organic matter. In both sites three experimental treatments consisting of traditional soil management and two variations of this one were evaluated. Traditional treatment implies low fertilizer and any chemical input, sowing annual crops during the rainy season and, in general, using low energy input. The crops planted were: legumes C3, oat C3, and a mixture of maizeC4 and beanC3, and wheatC3. The Improved and Organic treatments, had higher input of N and P as chemical fertilizers, and of organic manure (manure or compost), respectively. Soil samples were collected from the plow layer in Tlaxcala and in Michoacán, before C4 maize was planted. An Andisol from a pine-oak (C3 species) forest close to the Atecuaro site was also sampled up to 40 cm. This soil was considered a reference site not recently influenced by human activity. To analyze the d13C ratios of the SOM carbonate free samples, a routine combustion method and mass spectrometry (Finnigan MAT250) were used. In both agricultural sites a general excess of C3 species over C4 was evidenced through a mass balance equation derived from experimental d13C values (generally less than -20%o). The common feature for the soils under the Traditional and Traditional improved treatments was a C3 enrichment of the superficial SOM component compared to the underlying layers as a consequence of the dominance of the cultivated C3 species. A similar but more accentuated negative shift is also observed in the SOM from the forest soil (non-cultivated soil d13C -25.2), so the interpretation is uncertain. In the Traditional Organic treatment a clear and perceptible increment of d13C in the SOM carbon signature was observed. This was attributed mainly to the fact that cows manure may contain a lot of C4 coming from feedstuff rich in corn grain that is provided to the animals during grass shortage periods . However, the maize crop introduced in the rotation during the 3rd year had no major effect on the tepetates carbon isotopic signature. The stable isotopic carbon data corresponding to a short period (4 years) of observation in uniformly managed soil ecosystems showed that d13C changed due to the quality of the residues (relative abundance of C3/C4 species) incorporated to the SOC, but this memory is susceptible to undergo changes in the short term and could be rapidly reversed as a consequence of crop management.
La evolución de un suelo afectado por eventos naturales o externos puede ser interpretada según u... more La evolución de un suelo afectado por eventos naturales o externos puede ser interpretada según un Modelo de Estados y Transiciones (MET) que considere la interacción suelo-vegetación. En el caso que se presenta se demostró que la intensidad de la degradación influye directamente en la estabilización del C orgánico del suelo (COS) en función de la relación molar (Sio – Sid/ Alo- Ald) de tal manera que es posible establecer las posibles trayectorias en la degradación desde un bosque conservado hasta el suelo desnudo.
Potato (Solanum tuberosum) generally requires high amounts of phosphate fertilizer to reach econo... more Potato (Solanum tuberosum) generally requires high amounts of phosphate fertilizer to reach economically acceptable yields, particularly in soils originating from volcanic ash. This is a consequence of the potato plants low root density and the slow soil diffusion rate of phosphorus (P) in ...
Mediante el uso del marco
conceptual de los Modelos de Estados y
Transiciones (MET) se discute la... more Mediante el uso del marco conceptual de los Modelos de Estados y Transiciones (MET) se discute la relación entre la temperatura del suelo (Ts) y la respiración del mismo (Rs). El esquema de acoplamiento del sistema suelo-vegetación-atmósfera permite presentar argumentos y evidencia experimental que explica el porqué de las relaciones entre Ts y Rs, dependiendo del grado de acoplamiento de las componentes del sistema. Asimismo, se discuten las implicaciones de este acoplamiento en relación con los flujos de C y el cambio climático.
The soils of the Mexican Volcanic Belt are part of ecosystems subjected to strong human impact du... more The soils of the Mexican Volcanic Belt are part of ecosystems subjected to strong human impact during the last six centuries. One measurable characteristic of the soil is the stable carbon isotopic relation of the soil organic matter (SOM) or d13C. The d13C SOM parameter is a genetic characteristic of soil reflecting the relative proportion of C3 and C4 that comes from colonizing plants having different photosynthetic C pathway and is used as a high-spatial resolution tool to infer paleoenvironmental changes.The d13C mean signatures of C3 and C4 plants are -27 and -13 %o, respectively. This work focuses on short-term changes in d13C on soils subjected to controlled agricultural practices during 2002-2005 in two sites of Mexico with similar annual precipitation and temperature. The tepetate was broken up 20y ago and ameliorated with fertilizers and organic matter. In both sites three experimental treatments consisting of traditional soil management and two variations of this one were evaluated. Traditional treatment implies low fertilizer and any chemical input, sowing annual crops during the rainy season and, in general, using low energy input. The crops planted were: legumes C3, oat C3, and a mixture of maizeC4 and beanC3, and wheatC3. The Improved and Organic treatments, had higher input of N and P as chemical fertilizers, and of organic manure (manure or compost), respectively. Soil samples were collected from the plow layer in Tlaxcala and in Michoacán, before C4 maize was planted. An Andisol from a pine-oak (C3 species) forest close to the Atecuaro site was also sampled up to 40 cm. This soil was considered a reference site not recently influenced by human activity. To analyze the d13C ratios of the SOM carbonate free samples, a routine combustion method and mass spectrometry (Finnigan MAT250) were used. In both agricultural sites a general excess of C3 species over C4 was evidenced through a mass balance equation derived from experimental d13C values (generally less than -20%o). The common feature for the soils under the Traditional and Traditional improved treatments was a C3 enrichment of the superficial SOM component compared to the underlying layers as a consequence of the dominance of the cultivated C3 species. A similar but more accentuated negative shift is also observed in the SOM from the forest soil (non-cultivated soil d13C -25.2), so the interpretation is uncertain. In the Traditional Organic treatment a clear and perceptible increment of d13C in the SOM carbon signature was observed. This was attributed mainly to the fact that cows manure may contain a lot of C4 coming from feedstuff rich in corn grain that is provided to the animals during grass shortage periods . However, the maize crop introduced in the rotation during the 3rd year had no major effect on the tepetates carbon isotopic signature. The stable isotopic carbon data corresponding to a short period (4 years) of observation in uniformly managed soil ecosystems showed that d13C changed due to the quality of the residues (relative abundance of C3/C4 species) incorporated to the SOC, but this memory is susceptible to undergo changes in the short term and could be rapidly reversed as a consequence of crop management.
La evolución de un suelo afectado por eventos naturales o externos puede ser interpretada según u... more La evolución de un suelo afectado por eventos naturales o externos puede ser interpretada según un Modelo de Estados y Transiciones (MET) que considere la interacción suelo-vegetación. En el caso que se presenta se demostró que la intensidad de la degradación influye directamente en la estabilización del C orgánico del suelo (COS) en función de la relación molar (Sio – Sid/ Alo- Ald) de tal manera que es posible establecer las posibles trayectorias en la degradación desde un bosque conservado hasta el suelo desnudo.
Potato (Solanum tuberosum) generally requires high amounts of phosphate fertilizer to reach econo... more Potato (Solanum tuberosum) generally requires high amounts of phosphate fertilizer to reach economically acceptable yields, particularly in soils originating from volcanic ash. This is a consequence of the potato plants low root density and the slow soil diffusion rate of phosphorus (P) in ...
Mediante el uso del marco
conceptual de los Modelos de Estados y
Transiciones (MET) se discute la... more Mediante el uso del marco conceptual de los Modelos de Estados y Transiciones (MET) se discute la relación entre la temperatura del suelo (Ts) y la respiración del mismo (Rs). El esquema de acoplamiento del sistema suelo-vegetación-atmósfera permite presentar argumentos y evidencia experimental que explica el porqué de las relaciones entre Ts y Rs, dependiendo del grado de acoplamiento de las componentes del sistema. Asimismo, se discuten las implicaciones de este acoplamiento en relación con los flujos de C y el cambio climático.
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conceptual de los Modelos de Estados y
Transiciones (MET) se discute la relación entre la
temperatura del suelo (Ts) y la respiración del
mismo (Rs). El esquema de acoplamiento del
sistema suelo-vegetación-atmósfera permite
presentar argumentos y evidencia experimental
que explica el porqué de las relaciones entre Ts y
Rs, dependiendo del grado de acoplamiento de las
componentes del sistema. Asimismo, se discuten
las implicaciones de este acoplamiento en relación
con los flujos de C y el cambio climático.
conceptual de los Modelos de Estados y
Transiciones (MET) se discute la relación entre la
temperatura del suelo (Ts) y la respiración del
mismo (Rs). El esquema de acoplamiento del
sistema suelo-vegetación-atmósfera permite
presentar argumentos y evidencia experimental
que explica el porqué de las relaciones entre Ts y
Rs, dependiendo del grado de acoplamiento de las
componentes del sistema. Asimismo, se discuten
las implicaciones de este acoplamiento en relación
con los flujos de C y el cambio climático.