Abstract Plants accelerate chemical weathering of minerals through the production of carbonic acid during root respiration, root exudation, and uptake of ions. These plant processes are increased by elevated concentrations of atmospheric CO2 and may in turn affect mineral weathering. We seek to understand the effect of predicted atmospheric CO2 concentrations on plant-mediated soil mineral weathering. Phaseolus vulgaris (common bean) was grown in flow-through microcosms consisting of a mixture of 85% quartz and 15% apatite sands (by weight). Nutrient release from apatite was measured using plants grown under two atmospheric conditions: ambient CO2 (~400 ppm) and elevated CO2 (~1000 ppm). To sustain plant growth, a nutrient solution without calcium (Ca) or phosphorous (P) was supplied to the plants using peristaltic pumps. Unplanted microcosms receiving the same nutrient solution served as abiotic controls in both CO2 treatments. Using atomic absorption spectroscopy and colorimetry, Ca and P concentrations of the leachate and plant tissue were measured as proxies for apatite dissolution. Plants were harvested every 2 weeks during the 8-week experiment to understand how Ca and P release in the two CO2 treatments changed over time. After 8 weeks, P. vulgaris grown in elevated CO2 had a greater root to shoot ratio than plants grown in ambient CO2. Plants grown in elevated CO2 released more P than plants grown in ambient conditions, possibly due to greater demands for mineral nutrients. P was preferentially released by the plants and there were no significant differences in Ca released by plants. Both elevated and ambient planted microcosms had a lower pH than abiotic controls, likely due to root respiration, nutrient uptake and exudation of organic acids. Organic acids were not identified in the leachate likely due to their low concentrations and rapid breakdown. Plants released as much as 7 times more Ca than abiotic controls, regardless of CO2 concentrations. Biotic experiments released over 200 times more P than abiotic experiments. Our results show increased atmospheric CO2 can determine rhizosphere processes, which in turn affect weathering products. Thus, mineral nutrient fluxes and C sequestration in inorganic pools are likely to increase as CO2 concentrations rise.

中文翻译：

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菜豆（Phaseolus vulgaris）对 CO2 升高条件下磷灰石风化的影响

摘要 植物通过在根呼吸、根系分泌物和离子吸收过程中产生碳酸来加速矿物质的化学风化。大气二氧化碳浓度升高会增加这些植物过程，并可能反过来影响矿物风化。我们试图了解预测的大气 CO2 浓度对植物介导的土壤矿物风化的影响。Phaseolus vulgaris（普通豆）生长在由 85% 石英和 15% 磷灰石砂（按重量计）的混合物组成的流通微观世界中。使用在两种大气条件下生长的植物测量磷灰石的营养释放：环境 CO2 (~400 ppm) 和升高的 CO2 (~1000 ppm)。为了维持植物生长，使用蠕动泵向植物供应不含钙 (Ca) 或磷 (P) 的营养液。接受相同营养液的未种植微宇宙在两种 CO2 处理中均作为非生物对照。使用原子吸收光谱法和比色法，可以测量渗滤液和植物组织的 Ca 和 P 浓度，作为磷灰石溶解的代表。在为期 8 周的实验中，每 2 周收获一次植物，以了解两种 CO2 处理中 Ca 和 P 的释放如何随时间变化。8 周后，在升高的 CO2 中生长的 P. vulgaris 比在环境 CO2 中生长的植物具有更高的根茎比。生长在高 CO2 环境中的植物比生长在环境条件下的植物释放更多的 P，这可能是由于对矿质营养素的需求更大。植物优先释放P，植物释放的Ca无显着差异。高架和环境种植的微观世界的 pH 值都低于非生物对照，这可能是由于根呼吸、养分吸收和有机酸的渗出。由于有机酸浓度低且分解速度快，因此在渗滤液中未发现有机酸。无论 CO2 浓度如何，植物释放的 Ca 比非生物对照高 7 倍。生物实验释放的磷比非生物实验多 200 倍。我们的结果表明，大气中二氧化碳的增加可以决定根际过程，进而影响风化产物。因此，无机池中的矿物质养分通量和 C 固存可能会随着 CO2 浓度的升高而增加。由于有机酸浓度低且分解速度快，因此在渗滤液中未发现有机酸。无论 CO2 浓度如何，植物释放的 Ca 比非生物对照高 7 倍。生物实验释放的磷比非生物实验多 200 倍。我们的结果表明，大气中二氧化碳的增加可以决定根际过程，进而影响风化产物。因此，无机池中的矿物质养分通量和 C 固存可能会随着 CO2 浓度的升高而增加。由于有机酸浓度低且分解速度快，因此在渗滤液中未发现有机酸。无论 CO2 浓度如何，植物释放的 Ca 比非生物对照高 7 倍。生物实验释放的磷比非生物实验多 200 倍。我们的结果表明，大气中二氧化碳的增加可以决定根际过程，进而影响风化产物。因此，无机池中的矿物质养分通量和 C 固存可能会随着 CO2 浓度的升高而增加。