Urbanization Increases Grassland Carbon Pools: Effects Of Landscaping In Colorado's Front Range

Abstract

During the past few decades, urban and suburban developments have grown at unprecedented rates and extents with unknown consequences for ecosystem function. Carbon pools of soil and vegetation on landscaped properties were examined in the Front Range of Colorado, USA, in order to characterize vegetation and soils found in urban green spaces; analyze their aboveground biomass, vegetative C storage, and soil C storage; and compare these suburban ecosystem properties to their counterparts in native grassland and cultivated fields. Anthropogenic activities leave clear signatures on all three C compartments measured. Management level dominates the response of grass production, biomass, and N tissue concentration. This, in turn, influences the amount of C and N both stored in and harvested from sites. The site age dominates the amount of woody biomass as well as soil C and N. Soil texture only secondarily affects total soil carbon and total bulk density. Established urban green spaces harbor larger C pools, more than double in some cases, than native grasslands or agricultural fields on a per-area basis. Lawn grass produces more biomass and stores more C than local prairie or agricultural fields. Introduced woody vegetation comprises a substantial C pool in urban green spaces and represents a new ecosystem feature. After an initial decrease with site development, soil organic carbon (SOC) pools surpass those in grasslands within two decades. In addition to the marked increase of C pools through time, a shift in storage from belowground to aboveground occurs. Whereas grasslands store approximately 90% of C belowground, urban green spaces store a decreasing proportion of the total C belowground in soils through time, reaching approximately 70% 30-40 years after construction. Despite the substantial increase in C pools in this urban area, it is important to recognize that this shift is distinct from C sequestration since it does not account for a total C budget, including increased anthropogenic C emissions from these sites.

Integrated climate and land use change scenarios for California rangeland ecosystem services: wildlife habitat, soil carbon, and water supply

“…However, outcomes for SOC after grassland conversion to urban land uses are uncertain. For example, soil C can increase when converted to urban green spaces or lawns (Golubiewski 2006). Also, tillage of lands for cropland often leads to rapid declines in soil carbon (Lal 2002), though total ecosystem carbon may increase if grasslands are replaced by orchards (Kroodsma and Field 2006).…”

“…Variability in precipitation across climate projections creates uncertainty in the amount of water 2003-2006, 2037-2040, 2067-2070, and 2096-2099Landscape Ecol (2015 available in the future. New ensemble models show California becoming slightly more wet by 2100 (Flint and Flint 2014).…”

Estimating Net Primary Production of Turfgrass in an Urban-Suburban Landscape with QuickBird Imagery

“…Quantification of the contribution of urban vegetation to regional carbon budget is important for understanding and mitigating many aspects of carbon sinks and sources and global climate change [18,19]. Studies have shown that low density suburban areas, which are prevalent around many metropolitan regions and characterized by large proportions of vegetation, can be more productive than non-urban forest, native grasslands, and cultivated lands; thus at regional scale, carbon uptake from the atmosphere may be strengthened as a result of the rural land conversion [17,20,21] though urban development may have largely reduced the productivity of the land surface at continental scale [22]. Reliable methods and high resolution data are needed to help local agencies to facilitate the development of successful carbon management programs for monitoring and reducing urban carbon emission.…”

“…This approach has provided a wealth of valuable data, but only a small fraction of the area of interest can be surveyed since field measurements are labor intensive and expensive, and not all patches of vegetation within an urban landscape can be accounted for. Additionally, it is difficult to strictly adhere to a specific sampling design in landscape level inventory studies (e.g., permission to access private properties) and the methods used are not always consistent [20]. Therefore, it is difficult to compare the estimates generated from different studies.…”

Designing a carbon capture function into urban soils

“…The disturbance of soils and native vegetation on urbanization may release carbon from soils, but with reestablishment of vegetation cover these can re-accumulate organic carbon (Smetak et al, 2007). By the year 2000 the organic carbon density of soils in gardens in Colorado, USA, established in the 1950s, was approximately three times greater than in those established in the 1990s (Golubiewski, 2006). In the UK, soil carbon storage in arable and horticultural soils has been estimated at approximately 4.5 kg m -2 (Ostle et al, 2009), which is 36-53% lower than the values reported for public grassland and garden lawns in urban greenspace (Table 1).…”