Modelling carbon sink of urban street trees and soil in Helsinki, Finland
Authors: Havu Minttu , Kulmala Liisa , Riikonen Anu , Järvi Leena 
Published: March 2020

&lt;p&gt;A &lt;span&gt;high proportion of anthropogenic carbon dioxide emissions &lt;/span&gt;&lt;span&gt;originate from&lt;/span&gt;&lt;span&gt; urban areas, which has led cities to become interested in reducing their own emissions and &lt;/span&gt;&lt;span&gt;determining&lt;/span&gt;&lt;span&gt; how much carbon could be sequestered by their own vegetation and soil. &lt;/span&gt;&lt;span&gt;The challenge with the latter is that our current knowledge on carbon storage is based on data and models from natural and forest ecosystems, whereas&lt;/span&gt;&lt;span&gt; the response of vegetation and soil to environmental factors most probably is altered in urban green space where the soil conditions, water availability &lt;/span&gt;&lt;span&gt;and&lt;/span&gt;&lt;span&gt; temperature are highly variable.&lt;/span&gt; &lt;span&gt;T&lt;/span&gt;&lt;span&gt;herefore&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;ecosystem models &lt;/span&gt;&lt;span&gt;are required to &lt;/span&gt;&lt;span&gt;correctly account for urban vegetation&lt;/span&gt; &lt;span&gt;and soil &lt;/span&gt;&lt;span&gt;to understand &lt;/span&gt;&lt;span&gt;and quantify&lt;/span&gt;&lt;span&gt; the biogenic carbon cycle in urban areas. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;I&lt;/span&gt;&lt;span&gt;n this study, urban land surface model SUEWS &lt;/span&gt;&lt;span&gt;(&lt;/span&gt;&lt;span&gt;the &lt;/span&gt;&lt;span&gt;Surface Urban Energy and Water Balance Scheme&lt;/span&gt;&lt;span&gt;)&lt;/span&gt; &lt;span&gt;and &lt;/span&gt;&lt;span&gt;t&lt;/span&gt;&lt;span&gt;he soil carbon decomposition model Yasso&lt;/span&gt;&lt;span&gt;15&lt;/span&gt; &lt;span&gt;are used to simulate urban carbon cycle on two street&lt;/span&gt;&lt;span&gt;s&lt;/span&gt; &lt;span&gt;in Helsinki, Finland for years 2003-2016. &lt;/span&gt;&lt;span&gt;Curbside trees (&lt;em&gt;Alnus glutinosa &lt;/em&gt;and&lt;em&gt; Tilia &lt;/em&gt;&lt;/span&gt;&lt;em&gt;&lt;span&gt;x Vulgaris&lt;/span&gt;&lt;/em&gt;&lt;span&gt;) were planted while the two test streets were constructed in 2002. Thereafter&lt;/span&gt;&lt;span&gt;, carbon and water fluxes &lt;/span&gt;&lt;span&gt;and &lt;/span&gt;&lt;span&gt;pools&lt;/span&gt; &lt;span&gt;with detailed street tree soil composition&lt;/span&gt;&lt;span&gt;s&lt;/span&gt; &lt;span&gt;were&lt;/span&gt;&lt;span&gt; monitored in&lt;/span&gt;&lt;span&gt; 2002-2014. &lt;/span&gt;&lt;span&gt;SUEWS creates a local spatially variable temperature and specific humidity environment which is used in the model runs. &lt;/span&gt;&lt;span&gt;The modelled evaporation i&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt; evaluated against sap flow measurements and modelled soil moisture against soil moisture observations. &lt;/span&gt;&lt;span&gt;The &lt;/span&gt;&lt;span&gt;Yasso&lt;/span&gt;&lt;span&gt;15&lt;/span&gt;&lt;span&gt; model i&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt; evaluated against loss-on-ignition based soil carbon measurements &lt;/span&gt;&lt;span&gt;as &lt;/span&gt;&lt;span&gt;it has not been &lt;/span&gt;&lt;span&gt;previously &lt;/span&gt;&lt;span&gt;evaluated &lt;/span&gt;&lt;span&gt;in urban soils. &lt;/span&gt;&lt;span&gt;T&lt;/span&gt;&lt;span&gt;he &lt;/span&gt;&lt;span&gt;modelled&lt;/span&gt;&lt;span&gt; carbon dioxide flux combined with the &lt;/span&gt;&lt;span&gt;changes in the&lt;/span&gt;&lt;span&gt; soil carbon stock is used t&lt;/span&gt;&lt;span&gt;o estimate the carbon cycle of ur&lt;/span&gt;&lt;span&gt;ban street &lt;/span&gt;&lt;span&gt;trees and soils.&lt;/span&gt;&lt;/p&gt;