@article{PAR00008002,
  title = {{T}he role of savannas in the terrestrial {S}i cycle : a case-study from {L}amto, {I}vory {C}oast},
  author = {{A}lexandre, {A}. and {B}ouvet, {M}. and {A}bbadie, {L}uc},
  editor = {},
  language = {{ENG}},
  abstract = {{S}avannas currently occupy a fifth of the earth's land surface and are predicted to expand in the next few centuries at the expense of tropical forests, mainly as a result of deforestation and human fires. {C}an such a vegetation trend impact, through changes in plant {S}i cycling, the lithogenic silicon ({LS}i) release into soils (through chemical weathering) and the net dissolved {S}i ({DS}i) outputs from soils to stream water (through chemical denudation)? {T}he first step of an investigation requires quantifying the net {S}i fluxes involved in the plant/soil system. {H}ere, a schematic steady-state {S}i cycle, established for a tropical humid savanna ({L}amto, {I}vory {C}oast) that developed on a ferruginous soil and is subjected to annual fires, is presented. {E}rosion was assumed to be insignificant. {LS}i and biogenic {S}i ({BS}i under the form of phytoliths) pools were measured, and {S}i fluxes were estimated from {S}i concentrations and mass balance calculation. {I}dentification of plant and soil phytoliths indicated that the soil {BS}i pool is in equilibrium with the current {BS}i input by the savanna. {I}n the soil column, mixing between a young rapidly recycled {BS}i pool and an old stable {BS}i pool is attested by a mixing line equation. {S}torage of the old {BS}i pool is assimilated as a {BS}i output from the plant/soil system. {A} {BS}i output additionally occurs after annual fires, when ashes are exported. {B}oth {BS}i outputs decrease as much the {BS}i dissolution. {I}n order to uptake constant {DS}i flux, the savanna increases by three to eight times the net {LS}i release, depending upon the post-fire ash exportation scenario. {A} comparison between savanna and rainforest {S}i cycles that maximizes the differences in plant/soil systems and minimizes differences in climate is presented. {T}he comparison revealed that {BS}i storage is higher in the savanna soil than in the rainforest soil, mainly due to {BS}i production that is twice higher in the savanna (127 vs 67 kg/ha/yr). {T}he resulting {LS}i release that is enhanced by plant uptake is more than 1.5 higher in the savanna than in the rainforest (from 33 to 85 kg/ha/yr in the savanna vs 21 kg/ha/yr in the rainforest). {O}n the contrary, {DS}i output from soils to stream water, which is not controlled by plant {S}i cycling but more likely by the soil hydrological regime (or meteoric weathering), is close to twice as high in the rainforest/ferrallitic soil ecosystem (16 vs 9 kg/ha/yr). {T}his case study suggests that the predicted expansion of savannas at the expense of forests should significantly increase {DS}i uptake by plants, {BS}i storage in soils, {BS}i output with ash exportation, and, hence, {LS}i release through chemical weathering, without direct impact on {DS}i outputs from soils to stream water. {T}racks for further assessing the role of plant {S}i cycling on chemical weathering, {S}i and {C} cycles were suggested: 1) estimates of {BS}i fluxes that were wrongly based on the assumption that the amount of {DS}i leached out from soils is linked to the magnitude of plant {S}i cycling and/or to {BS}i concentration in soils should be reappraised and 2) changes in the magnitude of plant {S}i cycling should be accounted in geochemical carbon cycle models, for one of the plant-induced weathering mechanisms.},
  keywords = {silicon cycle ; savanna ; phytolith ; chemical weathering},
  booktitle = {},
  journal = {{G}lobal and {P}lanetary {C}hange},
  volume = {78},
  numero = {3-4},
  pages = {162--169},
  ISSN = {0921-8181},
  year = {2011},
  DOI = {10.1016/j.gloplacha.2011.06.007},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00008002},
}