Urban-induced changes in tree leaf litter accelerate decomposition

Abstract

Introduction: 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. Results: 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 CO 2 released from litter originating in urban habitats compared to 200 ± 13 mg CO 2 released from litter originating in periurban habitats in the climate chamber incubation. Conclusions: We conclude that the level of urbanization affects decomposition indirectly through alterations in leaf litter quality even over short urban to periurban distances.

Effects of Seasonality, Tree Species and Urban Green Space on Deciduous Leaf Litter Decomposition in Lithuania

“…Q. robur leaf litter decomposition showed small but significant differences between the urban green spaces, and the decomposition of T. cordata leaf litter showed no significance between the types of green spaces. Our findings are consistent with the results of Dorendorf et al [38] that leaf litter decomposition for peri-urban forest is slower compared to the other urban green spaces for A. platanoides and B. pendula but not for Q. robur and T. cordata. The rate of leaf litter decomposition has been shown to be an indicator of leaf quality, with faster increased rates of decomposition indicating poorer quality (i.e., less nutrients) [39].…”

Litter decomposition driven by soil fauna, plant diversity and soil management in urban gardens

“…In this study, we chose litter decomposition as model ecosystem function, due to its importance in maintaining soil quality in urban gardens (Schram-Bijkerk et al, 2018) and because of the lack of studies analysing the effect of urbanisation on litter decomposition (Dorendorf et al, 2015). We investigated direct and indirect effects of environmental factors and management practices on litter decomposition along an urban intensity gradient, which was measured as the local temperature increase due to urban warming.…”

High carbon losses from established growing sites delay the carbon sequestration benefits of street tree plantings – A case study in Helsinki, Finland

“…The contribution of litter and prunings to overall tree C sequestration appeared large for the still rather small case study trees. However, the literature-based decay factors may not have performed well under our conditions; the contradictory results concerning urban vs. rural litter decomposition rates (Pouyat et al, 1997;Pouyat and Carreiro, 2003;Nikula et al, 2010;Dorendorf et al, 2015) indicate that the processes related to urban litter are not yet well understood. When the soil surface is sealed, the aboveground litter is likely lost from the tree-soil system, warranting leaving it out of the C sequestration estimates.…”