Effects of Soil Texture on Belowground Carbon and Nutrient Storage in a Lowland Amazonian Forest Ecosystem |
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Authors: | Whendee L Silver Jason Neff Megan McGroddy Ed Veldkamp Michael Keller Raimundo Cosme |
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Institution: | Department of Environmental Sciences, Policy, and Management, University of California, 151 Hilgard Hall, Berkeley, California 94720, USA, US Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA, US Institut fuer Bodenkunde und Waldernaehrung, Universitaet Goettingen, Buesgenweg 237077 Goettingen, Germany, DE The International Institute of Tropical Forestry, USDA Forest Service, Call Box 25000 Rio Piedras, Puerto Rico 00928, USA, US EMBRAPA Amaz?nia Oriental, Santarém, Pará, Brazil, BR
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Abstract: | Soil texture plays a key role in belowground C storage in forest ecosystems and strongly influences nutrient availability
and retention, particularly in highly weathered soils. We used field data and the Century ecosystem model to explore the role
of soil texture in belowground C storage, nutrient pool sizes, and N fluxes in highly weathered soils in an Amazonian forest
ecosystem. Our field results showed that sandy soils stored approximately 113 Mg C ha-1 to a 1-m depth versus 101 Mg C ha-1 in clay soils. Coarse root C represented a large and significant ecosystem C pool, amounting to 62% and 48% of the surface
soil C pool on sands and clays, respectively, and 34% and 22% of the soil C pool on sands and clays to 1-m depth. The quantity
of labile soil P, the soil C:N ratio, and live and dead fine root biomass in the 0–10-cm soil depth decreased along a gradient
from sands to clays, whereas the opposite trend was observed for total P, mineral N, potential N mineralization, and denitrification
enzyme activity. The Century model was able to predict the observed trends in surface soil C and N in loams and sands but
underestimated C and N pools in the sands by approximately 45%. The model predicted that total belowground C (0–20 cm depth)
in sands would be approximately half that of the clays, in contrast to the 89% we measured. This discrepancy is likely to
be due to an underestimation of the role of belowground C allocation with low litter quality in sands, as well as an overestimation
of the role of physical C protection by clays in this ecosystem. Changes in P and water availability had little effect on
model outputs, whereas adding N greatly increased soil organic matter pools and productivity, illustrating the need for further
integration of model structure and tropical forest biogeochemical cycling.
Received 3 March 1999; accepted 27 August 1999. |
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Keywords: | : roots soil carbon century model soil texture biogeochemistry tropics |
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