Department of Biology, Boston University, Boston, MA, 02215, USA.
Department of Earth and Environment, Boston University, Boston, MA, 02215, USA.
Environ Pollut. 2016 May;212:433-439. doi: 10.1016/j.envpol.2016.01.012. Epub 2016 Feb 23.
Urban areas are the dominant source of U.S. fossil fuel carbon dioxide (FFCO2) emissions. In the absence of binding international treaties or decisive U.S. federal policy for greenhouse gas regulation, cities have also become leaders in greenhouse gas reduction efforts through climate action plans. These plans focus on anthropogenic carbon flows only, however, ignoring a potentially substantial contribution to atmospheric carbon dioxide (CO2) concentrations from biological respiration. Our aim was to measure the contribution of CO2 efflux from soil respiration to atmospheric CO2 fluxes using an automated CO2 efflux system and to use these measurements to model urban soil CO2 efflux across an urban area. We find that growing season soil respiration is dramatically enhanced in urban areas and represents levels of CO2 efflux of up to 72% of FFCO2 within greater Boston's residential areas, and that soils in urban forests, lawns, and landscaped cover types emit 2.62 ± 0.15, 4.49 ± 0.14, and 6.73 ± 0.26 μmolCO2 m(-2) s(-1), respectively, during the growing season. These rates represent up to 2.2 times greater soil respiration than rates found in nearby rural ecosystems in central Massachusetts (MA), a potential consequence of imported carbon amendments, such as mulch, within a general regime of landowner management. As the scientific community moves rapidly towards monitoring, reporting, and verification of CO2 emissions using ground based approaches and remotely-sensed observations to measure CO2 concentrations, our results show that measurement and modeling of biogenic urban CO2 fluxes will be a critical component for verification of urban climate action plans.
城市是美国化石燃料二氧化碳（FFCO2）排放的主要来源。在没有具有约束力的国际条约或美国联邦温室气体监管政策的情况下，城市也通过气候行动计划成为温室气体减排的领导者。然而，这些计划仅关注人为碳流，忽略了生物呼吸对大气二氧化碳（CO2）浓度可能产生的大量贡献。我们的目的是使用自动 CO2 通量系统测量土壤呼吸产生的 CO2 通量对大气 CO2 通量的贡献，并利用这些测量结果对城市土壤 CO2 通量进行建模。我们发现，城市地区的土壤呼吸在生长季节显著增强，在波士顿大都市区的居民区，土壤呼吸产生的 CO2 通量高达 FFCO2 的 72%，城市森林、草坪和景观覆盖类型的土壤在生长季节分别排放 2.62±0.15、4.49±0.14 和 6.73±0.26 μmolCO2 m(-2) s(-1)。这些速率比马萨诸塞州中部（MA）附近农村生态系统中的速率高出 2.2 倍，这是由于土地所有者管理下的一般制度中引入了碳肥等进口碳改良剂的潜在后果。随着科学界迅速转向使用地面方法和遥感观测来监测、报告和验证 CO2 排放，我们的研究结果表明，测量和建模生物成因的城市 CO2 通量将是验证城市气候行动计划的关键组成部分。
