Abstract
The role of urban areas in the global carbon cycle has so far not been studied conclusively. Locally, urbanization might affect decomposition within urban boundaries. So far, only few studies have examined the effects of the level of urbanization on decomposition. This study addresses the influence of the level of urbanization on decomposition processes. It explores whether potential influences are exerted through leaf litter quality alterations or through direct effects of decomposition site’s level of urbanization. Leaf litter of five different tree species was sampled at urban and periurban sites. Decomposition of this litter was analyzed in three different experiments: a climate chamber incubation, a reciprocal litterbag transplant at urban and periurban sites, and a common garden litterbag transplant. Decomposition site’s level of urbanization did not show a significant effect. However, in all species, when significant differences were observed, leaf litter of urban origin decomposed significantly faster than leaf litter of periurban origin. This effect was observed in all three experiments. In the reciprocal litter transplant experiment, 62% ± 3% mass loss in litter of urban origin compared to 53% ± 3% in litter of periurban origin was observed. The difference was not as pronounced in the other two experiments, with 94% ± 1% mass loss of litter originating in urban habitats compared to 92% ± 1% mass loss of litter originating in periurban habitats in the common garden experiment and 225 ± 13 mg CO2 released from litter originating in urban habitats compared to 200 ± 13 mg CO2 released from litter originating in periurban habitats in the climate chamber incubation. We conclude that the level of urbanization affects decomposition indirectly through alterations in leaf litter quality even over short urban to periurban distances.
Highlights
The role of urban areas in the global carbon cycle has so far not been studied conclusively
The difference was not as pronounced in the other two experiments, with 94% ± 1% mass loss of litter originating in urban habitats compared to 92% ± 1% mass loss of litter originating in periurban habitats in the common garden experiment and 225 ± 13 mg CO2 released from litter originating in urban habitats compared to 200 ± 13 mg CO2 released from litter originating in periurban habitats in the climate chamber incubation
Despite the pronounced difference found in the climate chamber incubation for Populus with regard to origin, when Populus data were excluded from the analysis, the difference between urban and periurban origin was still significant (61% ± 3% and 52 ± 3% mean mass loss, respectively; data not shown, p ≤ 0.05)
Summary
The role of urban areas in the global carbon cycle has so far not been studied conclusively. This study addresses the influence of the level of urbanization on decomposition processes. Leaf litter of five different tree species was sampled at urban and periurban sites Decomposition of this litter was analyzed in three different experiments: a climate chamber incubation, a reciprocal litterbag transplant at urban and periurban sites, and a common garden litterbag transplant. Cities affect the global carbon cycle through anthropogenic release of CO2 and storage of organic carbon but have long been observed to influence decomposition (e.g., Fenn and Dunn 1989). Decomposition is a key component in the carbon cycle, as carbon bound in biomass is either released into the atmosphere as CO2 or stabilized by humification processes into long-lived soil organic matter. The term decomposition is used to describe the net mass loss of biomass (Berg and McClaugherty 2008)
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