Organic carbon hidden in urban ecosystems

Abstract

Urbanization is widely presumed to degrade ecosystem services, but empirical evidence is now challenging these assumptions. We report the first city-wide organic carbon (OC) budget for vegetation and soils, including under impervious surfaces. Urban soil OC storage was significantly greater than in regional agricultural land at equivalent soil depths, however there was no significant difference in storage between soils sampled beneath urban greenspaces and impervious surfaces, at equivalent depths. For a typical U.K. city, total OC storage was 17.6 kg m−2 across the entire urban area (assuming 0 kg m−2 under 15% of land covered by buildings). The majority of OC (82%) was held in soils, with 13% found under impervious surfaces, and 18% stored in vegetation. We reveal that assumptions underpinning current national estimates of ecosystem OC stocks, as required by Kyoto Protocol signatories, are not robust and are likely to have seriously underestimated the contributions of urban areas.

Vegetation Type and Age Drive Changes in Soil Properties, Nitrogen, and Carbon Sequestration in Urban Parks under Cold Climate

“…Further, since root turnover is one of the most important mechanisms by which organic matter enters the soil, it can determine the distribution of C in the soil profile (Jobbagy and Jackson, 2000). Similarly to previous studies (Golubiewski, 2006;Raciti et al, 2011;Edmondson et al, 2012Edmondson et al, , 2014bLivesley et al, 2016) we showed that soil variables, except soil pH, were sensitive to soil depth, and OM, tot-C and tot-N decreased and the soil C/N ratio increased with soil depth. However, this pattern was rather consistent across the targeted vegetation types and park ages, suggesting that plant roots have a negligible effect on these soil variables.…”

“…Although, urban home-yards and other intensively managed soils in the USA can sequester considerable amounts of C and N (Easton and Petrovic, 2008;Pouyat et al, 2010;Raciti et al, 2011), few have studied this topic in European cities (see Edmondson et al, 2012Edmondson et al, , 2014b. The control of C and N sequestration in urban greenspaces by plants differing in eco-physiology and whether these effects depend on the age of the greenspace remain virtually unknown.…”

“…As a result, soil OM and its importance in soil functioning (Franzluebbers, 2002;Lal, 2010) make surface soils primary drivers of soil-derived ecosystem services-also in urban settings (Lorenz and Lal, 2009;Edmondson et al, 2012). Although, deeper soil layers may also store considerable amounts of C and N in home-yards and other urban turf-grass habitats (Pouyat et al, 2010), little is known about how plant species or greenspace age influence the distribution of OM, C and N in urban soil profiles.…”

Managing soil carbon stocks to enhance the resilience of urban ecosystems

“…However, SOC stocks were not affected by surface cover (i.e., vegetated or capped).. Edmondson et al (2012) concluded that the contribution of urban ecosystems to national organic C inventories cannot be neglected.…”

“…The soil types did not affect urban SOC stocks but garden management practices such as the addition of peat, composts, and mulches, and cultivation of trees and shrubs contributed to greater SOC stocks in Leicester to 21-cm depth (Edmondson et al, 2014). Previously, Edmondson et al (2012) reported that urban soils in Leicester stored more SOC to 100-cm depth than regional arable soils. Specifically, SOC stocks for non-residential and residential land were 161 and 199 Mg C ha -1 (Table 2).. About 42% of the urban SOC stock to 100-cm depth in…”