Urban soils as hotspots of anthropogenic carbon accumulation

Urban soils as hotspots of anthropogenic carbon accumulation

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  Urban soils ashotspots of anthropogenic carbon accumulation Viacheslav Vasenev,1 Yakov Kuzyakov2 & Ivan Vasenev3 1 RUDN University, Moscow; 2 George-August University, Goettingen; 3 RTSAU, Moscow Global Symposium on soil organic carbon-2017
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  Urbanization – globaltendency  World population will exceed 9 billion people by 2050 (FAO, 2013)  More than 70% of world population will live in cities by then
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  Urbanization Traditionally urbanization was relatedto negative environmental impacts  Recently the potential of urban areas to provide important soil functions and services is highlighted Natural and agricultural landscapes Green zonesBuild-up areas
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  Driving factors behindurban soil’s formation and transformation Slope terracing «Urban heat island» Plant species introduction Wastes and landfills Soil sealing Soil construction Indirect anthropogenic influence Direct anthropogenic influence
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  Why soil carbon?Soil functions  Protection of humans and environment  Biomass production  General reservoir  Physical basis of human activities  Source of raw materials  Geogenic and cultural heritage Blum, 2005  Water and nutrient cycling  Ground water protection  Basis for organisms’ life  Land for settlements  Land for agriculture  Deposition of raw materials … BBodSchG, 1998  Nutrient cycling  Water filtering and buffering  Biodiversity and habitat  Resistance and resilience  Physical stability and support Andrews et al, 2004 !!! 30 to 50% of distinguished soil functions are directly or indirectly related to soil carbon
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  ESs’ categories (TEEB,2010)ESs’ categories (TEEB, 2010) !!! 25 to 40% of distinguished ecosystem services are directly or indirectly related to soil carbon Food Water  Raw materials Genetic resources Medical resources Ornamental resources Provisioning Air quality regulation Climate regulation Moderation of extreme events Regulation of water flows Water treatment Erosion prevention Maintenance of soil fertility Regulating •Aesthetic information •Opportunities for recreation and tourism •Inspiration of culture, art and design •Spiritual experience Cultural Habitat Maintenance of life cycles of migratory species Maintenance of genetic diversity Why soil carbon? Ecosystem services (ES)
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  Aim of thereview study  To analyze the global pattern of C stocks in urban soils as compared to their natural ones  To analyze factors of intra- and inter- city variability of C stocks  To compare profile distribution of C forms stored in urban soils, compared to natural ones  To propose the main mechanisms of C accumulation in urban soils  To estimate C accumulation time in urban soils
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  Materials and methods 118cities 770 values SOC, SIC and BC stocks 5 depths
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  Global patterns ofC stocks in urban soils Urban SOC stocks are usually greater than those of natural soils  Urban soils in cold and temperate climate often store more SOC than those in tropical and arid climates
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  Inter-city variability inSOC stocks Generally, the larger is a city (in terms of extent and population) the less are average topsoil SOC stocks The largest urban SOC stocks are related to cultural layers of medieval cities
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  Intra-city variability inSOC stocksIntra-city variability in SOC stocks Public and residential areas usually stored more SOC than all the other functional zones with the maximal contribution from subsoils and cultural layers
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  ““Hidden” C andN stocks in urban subsoilsHidden” C and N stocks in urban subsoils Substantial amounts of SOC, SIC and N have been sequestered in the subsoils, cultural layers and sealed soils, underlining the importance of these ‘hidden’ stocks for C assessments.
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  Profile distribution ofC and N stocksProfile distribution of C and N stocks
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  Mechanism of CaccumulationMechanism of C accumulation 1) C inputs from suburban-areas (e.g. transfer of food, wood and raw materials); 2) C provisioning and redistribution inside the city (e.g. xenobiotics, soot and charcoal); 3) in situ transformations (e.g. sealing, over- compaction and water-logging)
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  C accumulation ratein urban soilsC accumulation rate in urban soils Urban soils growth rate ~ 50 cm/ century Carbon accumulatio n in urban soils ~ 20-30 kg C m-2 per century
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  Conclusions  The estimatedC stocks in the investigated urban soils generally were up to 3-5 times higher than in background natural soils  SOC and BC stocks in the analyzed urban soils often positively correlated with city latitude  City size and age were the main factors explaining inter-city variability of soil C stocks  Intra-city variability of soil C stocks was dominated by their functional zoning  Large stocks of SOC and SIC are located in subsoils (below 30 cm) and cultural layers (below 100 cm) of sealed soils  Urban soils grow upward by about 50 cm per century, corresponding to C accumulation rate of 20-30 kg C m-2 per century
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  Thank you forattention !
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