Changes in land use driven by urbanization impact nitrogen cycling and the microbial community composition in soils

Abstract

Transition of populations from rural to urban living causes landscape changes and alters the functionality of soil ecosystems. It is unclear how this urbanization disturbs the microbial ecology of soils and how the disruption influences nitrogen cycling. In this study, microbial communities in turfgrass-grown soils from urban and suburban areas around Xiamen City were compared to microbial communities in the soils from rural farmlands. The potential N2O emissions, potential denitrification activity, and abundances of denitrifiers were higher in the rural farmland soils compared with the turfgrass soils. Ammonia oxidizing archaea (AOA) were more abundant than ammonia oxidizing bacteria (AOB) in turfgrass soils. Within turfgrass soils, the potential nitrification activities and AOA abundances were higher in the urban than in the suburban soils. These results indicate a more pivotal role of AOA in nitrification, especially in urban soils. Microbial community composition was distinctly grouped along urbanization categories (urban, suburban, and rural) classified according to the population density, which can in part be attributed to the differences in soil properties. These observed changes could potentially have a broader impact on soil nutrient availability and greenhouse gas emissions.

Urban Grassland Management Implications for Soil C and N Dynamics: A Microbial Perspective

“…A key feature of urbanization is the expansion of suburban and exurban developments consisting of larger parcel sizes where residential turfgrass lawns are a major land cover type (Robbins and Birkenholtz, 2003;Pouyat et al, 2009;Wang et al, 2017;Ignatieva and Hedblom, 2018). In the United States, where more than 80% of the population lives in urban areas (US Census Bureau, 2011), turfgrass landscapes, including residential, commercial, and institutional lawns, parks, athletic fields, and golf courses, make up roughly 2% of the total terrestrial land area-an area larger than the state of Georgia (Milesi et al, 2005).…”

“…Soil microorganisms mediate many fundamental belowground ecological processes, such as nutrient cycling and SOM accumulation or depletion, thus even typical urban grassland management practices such as mowing, the return or removal of mowed-off grass clippings, irrigation, fertilization, lawn species composition, or soil disturbance, have the potential to affect soil microbial structure and function. Changes in soil microbial processes may have tremendous influence on long-term C and N dynamics, including determining the fate of SOM in urban grasslands (Shi et al, 2012;Zhalnina et al, 2015;Crouch et al, 2017;Wang et al, 2017). Shifts in the composition of the soil microbiome could signify alterations to microbial functions that regulate biogeochemical transformations and other valuable ecosystem services (Shi et al, 2007(Shi et al, , 2012.…”

“…Shifts in the composition of the soil microbiome could signify alterations to microbial functions that regulate biogeochemical transformations and other valuable ecosystem services (Shi et al, 2007(Shi et al, , 2012. Despite the complexity and heterogeneous nature of soils, research has shown that soil microbiota respond to changes in environmental conditions and management practices that are at resolutions detectable with standard sequencing approaches (Janssen, 2006;Fierer et al, 2009a;Crouch et al, 2017;Wang et al, 2017). While relative abundances and diversity matrices of broad taxa can be tracked to show microbiome structural changes, soil functional attributes are also detectable (Schimel et al, 2005;Isobe and Ohte, 2014;Reisinger et al, 2016;Wang et al, 2017).…”

“…Despite the complexity and heterogeneous nature of soils, research has shown that soil microbiota respond to changes in environmental conditions and management practices that are at resolutions detectable with standard sequencing approaches (Janssen, 2006;Fierer et al, 2009a;Crouch et al, 2017;Wang et al, 2017). While relative abundances and diversity matrices of broad taxa can be tracked to show microbiome structural changes, soil functional attributes are also detectable (Schimel et al, 2005;Isobe and Ohte, 2014;Reisinger et al, 2016;Wang et al, 2017). Soil environmental controls on microbially-mediated processes, such as substrate availability, redox status, and pH, strongly influence soil microbial dynamics (Isobe and Ohte, 2014;Reisinger et al, 2016;Wang et al, 2017).…”

“…While relative abundances and diversity matrices of broad taxa can be tracked to show microbiome structural changes, soil functional attributes are also detectable (Schimel et al, 2005;Isobe and Ohte, 2014;Reisinger et al, 2016;Wang et al, 2017). Soil environmental controls on microbially-mediated processes, such as substrate availability, redox status, and pH, strongly influence soil microbial dynamics (Isobe and Ohte, 2014;Reisinger et al, 2016;Wang et al, 2017). In urban grasslands, much of these environmental variables are managed, including organic matter levels (mowing, topdressing with compost), soil moisture (irrigation), soil pH (liming), and nutrient additions (fertilizer applications), with potential impacts to soil microbiota and their functions.…”