Dissolved CO2 in small catchment streams of eastern Amazonia: A minor pathway of terrestrial carbon loss
Dissolved CO2 in small catchment streams of eastern Amazonia: A minor pathway of terrestrial carbon loss
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DOI：
10.1029/2009jg001202
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发表时间：
2010-12
影响因子：
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通讯作者：
E. Davidson;R. O. Figueiredo;D. Markewitz;A. Aufdenkampe
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文献类型：
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作者：
E. Davidson;R. O. Figueiredo;D. Markewitz;A. Aufdenkampe
[1]土壤中二氧化碳（CO2）的产生会导致地下水中溶解的游离CO2（pCO 2）过饱和，随后随着地下水进入溪流和河流而逃逸到大气中。这一过程可能是陆地固定碳返回大气的重要途径。我们测量pCO 2每月在多个站点沿着三个流从他们的源头在残留的成熟森林通过多个土地覆盖在巴西的帕拉。上游pCO 2平均值为19，000 μatm，下游下降至约4，500 μatm。在两个小的原始成熟森林集水区的源头测得类似的值。两种方法被用来估计地下水pCO 2逃逸：假设水源pCO 2测量反映了传入的地下水pCO 2或所有进入溪流水与先前测得的深层土壤CO2平衡。根据这些假设，陆地环境通过水生物逃避pCO 2而造成的损失为0.02-0.15 Mg C ha−1陆地面积yr−1，这比土壤呼吸和净初级生产力的年度估计值低2-3个数量级。然而，下游的pCO 2值，似乎是在准稳定状态表明其他C源，如水生初级生产，土壤侵蚀，溶解有机质，或从河边植被凋落物输入的贡献。因此，横向pCO 2损失从地下水流是轻微的，这一地区的大多数陆地生态系统，虽然C损失流可能是显着的河岸生态系统或地区的净陆地预算经历侵蚀。
[1] Production of carbon dioxide (CO2) in soils can lead to supersaturation of dissolved free CO2 (pCO2) in groundwater, which later evades to the atmosphere as groundwater enters streams and rivers. This process could be a significant pathway for return of terrestrially fixed C to the atmosphere. We measured pCO2 monthly over two years at multiple stations along three streams from their headwaters in remnant mature forests through multiple land covers in Para, Brazil. The pCO2 averaged 19,000 μatm in headwaters and decreased to about 4,500 μatm downstream. Similar values were measured in headwaters of two small pristine mature forest catchments. Two approaches were used to estimate groundwater pCO2 evasion: assuming that headwater pCO2 measurements reflected incoming groundwater pCO2 or that all entering stream water was in equilibrium with previously measured deep soil CO2. With these assumptions, losses from the terrestrial environment through aquatic evasion of pCO2 would be 0.02–0.15 Mg C ha−1 of land area yr−1, which is about 2–3 orders of magnitude lower than annual estimates of soil respiration and net primary productivity. However, downstream pCO2 values that appear to be in quasi-steady state indicate contributions from other C sources, such as aquatic primary production, soil erosion, dissolved organic matter, or litter inputs from streamside vegetation. Hence, lateral pCO2 loss from groundwater to streams is minor for most of the terrestrial ecosystems of this region, although C loss to streams could be significant for net terrestrial budgets in riparian ecosystems or areas experiencing erosion.