Department of Forestry & Natural Resources, Division of Environmental & Ecological Engineering, Purdue University, 715 W State St, West Lafayette, IN 47907, USA; Department of Earth and Environment, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, USA.
Department of Earth and Environment, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, USA.
Sci Total Environ. 2017 Aug 15;592:366-372. doi: 10.1016/j.scitotenv.2017.03.028. Epub 2017 Mar 18.
Many ecosystem models incorrectly treat urban areas as devoid of vegetation and biogenic carbon (C) fluxes. We sought to improve estimates of urban biomass and biogenic C fluxes using existing, nationally available data products. We characterized biogenic influence on urban C cycling throughout Massachusetts, USA using an ecosystem model that integrates improved representation of urban vegetation, growing conditions associated with urban heat island (UHI), and altered urban phenology. Boston's biomass density is 1/4 that of rural forests, however 87% of Massachusetts' urban landscape is vegetated. Model results suggest that, kilogram-for-kilogram, urban vegetation cycles C twice as fast as rural forests. Urban vegetation releases (R) and absorbs (GEE) the equivalent of 11 and 14%, respectively, of anthropogenic emissions in the most urban portions of the state. While urban vegetation in Massachusetts fully sequesters anthropogenic emissions from smaller cities in the region, Boston's UHI reduces annual C storage by >20% such that vegetation offsets only 2% of anthropogenic emissions. Asynchrony between temporal patterns of biogenic and anthropogenic C fluxes further constrains the emissions mitigation potential of urban vegetation. However, neglecting to account for biogenic C fluxes in cities can impair efforts to accurately monitor, report, verify, and reduce anthropogenic emissions.
许多生态系统模型错误地将城市地区视为没有植被和生物成因碳（C）通量的地方。我们试图利用现有的、全国可用的数据产品来改进城市生物量和生物成因 C 通量的估计。我们使用一种生态系统模型，该模型综合了对城市植被、与城市热岛（UHI）相关的生长条件以及改变的城市物候的改进表示，来描述美国马萨诸塞州整个城市 C 循环中的生物成因影响。波士顿的生物量密度是农村森林的 1/4，但马萨诸塞州 87%的城市景观都是植被覆盖的。模型结果表明，城市植被每公斤的 C 循环速度是农村森林的两倍。城市植被的释放（R）和吸收（GEE）分别相当于该州最城市化地区人为排放的 11%和 14%。虽然马萨诸塞州的城市植被完全封存了该地区较小城市的人为排放，但波士顿的 UHI 使年度 C 储存减少了>20%，从而使植被仅抵消了 2%的人为排放。生物成因和人为 C 通量的时间模式之间的不同步进一步限制了城市植被减少人为排放的潜力。然而，忽视城市生物成因 C 通量的作用可能会影响准确监测、报告、核实和减少人为排放的努力。
