INVESTIGADORES
JOBBAGY GAMPEL Esteban Gabriel
artículos
Título:
Grazing effects on belowground C and N stocks along a network of cattle exclosures in temperate and subtropical grasslands of South America
Autor/es:
G PIÑEIRO; JM PARUELO; EG JOBBÁGY; RB JACKSON; M OESTERHELD
Revista:
GLOBAL BIOGEOCHEMICAL CYCLES
Editorial:
American Geophysical Union
Referencias:
Lugar: Washington DC; Año: 2009 vol. 23 p. 1 - 1
ISSN:
0886-6236
Resumen:
We evaluated the effects of grazing on C and N belowground pools by comparing9 15 grazing-exclosure pairs across the Rı´o de la Plata grasslands of Uruguay and10 Argentina. We measured C and N pools of belowground biomass, particulate organic11 matter (POM), and the mineral associated organic matter (MAOM) in the top meter of the12 soil. Grazing exclusion in the Rı´o de la Plata grasslands promoted (1) decreased13 belowground biomass stocks across all sites, (2) increased SOC and SON stocks in14 upland soils, and (3) decreased stocks in shallow and lowland soils. In all cases, SOC and15 SON variations were largely derived by changes in MAOM stocks that maintained16 their C:N ratios unchanged. In contrast, stocks of the labile POM fractions changed little,17 but C:N ratios of these fractions decreased after grazing removal. We hypothesize that18 changes in SOM contents between grazed and ungrazed stands result from the balance19 between changes in belowground N allocation patterns (root N retention hypothesis),20 the ability of the soil to retain the extra N available after the exclusion of herbivores, and21 the cessation of volatilization and leaching from urine and dung patches (N loss22 hypothesis). On the basis of our results we suggest that the relative importance of these23 two cooccurring mechanisms will shape grazing effects on SOM stocks, depending on24 soil properties, including texture, pH and soil depth, and vegetation type,25 particularly allocation patterns and C:N ratios of different plant species
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