The simplification of urban ecosystems structure affects soil processes and soil biodiversity Alessandro Ossola 1, Hahs, A.C. 2, Christie, F.J. 3, Nash, M.A. 4, Livesley, S.J 1 1 Green Infrastructure Research Group, DRMG, University of Melbourne, Melbourne, Australia. 2 Australian Research Centre for Urban Ecology, University of Melbourne, Melbourne, Australia. 3 Department of Forest and Ecosystem Science, University of Melbourne, Australia. 4 South Australian Research and Development Institute, Adelaide, Australia.

Urban ecosystem change: structure

Urban ecosystem structure High-complexity park (HCP) High-complexity remnant (HCR) Low-complexity park (LCP) HCP and LCP age ranges from 43 to 100 years since establishment

Research questions is the simplification of the structure of urban ecosystems affecting soil processes (decomposition)? how does the simplification of the structure affect the microclimate of the surface decomposition environment? does the variation in soil biogeochemical processes correlate with a variation in soil fauna and biodiversity?

Materials & Methods SOIL Soil texture, bulk density, strength Soil moisture Saturated hydraulic conductivity * Unsaturated hydraulic conductivity * Soil water holding capacity * Aggregates distribution * C, N, SOM * LITTER Litter mass Temperature Litter water holding capacity * Decomposition rates CLPP (Ecoplates ® ) VEGETATION Structure Sky view factor (SVF) * Canopy interception * * (results not presented here)

Materials & Methods LITTERBAGS EXPERIMENT 0.2 mm (microbes) and 6 mm (macro-decomposers) bags 2 substrates – Eucalyptus globulus leaves (C/N=41) pea straw (C/N=57) 3 collection events at 70, 160 and 365 days. 30 plots, 3 reps, total of 1080 litterbags COMMUNITY-LEVEL PHYSIOLOGICAL PROFILING Biolog Ecoplates ® on soil samples collected below the litterbags and Eucalyptus litter from the last set of litterbags.

Results – Soil physical properties LCP HCR HCP Bulk density 0-10cm (g/cm 3 ) Soil texture (90 measurements), Bulk density (300 measurements),

Results – litter microclimate

Results – decomposition

Results – meso-macrodecomposers

Results – microbial functional diversity LCP (red), HCP (orange), HCR (green) No differences in substrate diversity between the 3 ecosystem types both in litter and soil

Results – microbial decomposition lm(formula = k2L ~ T_jul_mean + T_oct_mean + SMsep13 + SMnov13 + H24 + H48 + H72 + H96) Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 1.403e e T_jul_mean 1.054e e T_oct_mean e e * SMsep e e * SMnov e e ** H e e H e e H e e H e e Signif. codes: 0 ‘***’ ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: on 56 degrees of freedom (25 observations deleted due to missingness) Multiple R-squared: , Adjusted R-squared: F-statistic: on 8 and 56 DF, p-value:

Conclusions The simplification of urban ecosystems affects decomposition processes and therefore C sequestration and soil health in the long term In simplified ecosystems meso-macrodecomposers diversity is similar to more complex ecosystems, but their abundance is lower Litter microbial communities are functionally similar and microbial decomposition activity might be indirectly driven by the ecosystem structure via a control on the microclimate

Implications for UGEC 1)What are the key lessons learned from your research as related to the session topic and the broader conference theme under which it falls? The evaluation of services and benefits provided by urban ecosystems must be based on the quantification of the underlying processes and functions The simplification or urban ecosystems affects key soil processes and the relative ecosystem services Microclimate and soil organisms are also affected by urban ecosystem simplification

Implications for UGEC 2) How does your research add to the broader knowledge base of Urbanization and Global Environmental Change Simplification is a common but underlooked driver of change in urban ecosystems compared to other drivers (e.g. fragmentation, homogeneization, etc) Simplification might have relevant effects on other processes, biodiversity and the underlying ecosystem services

Implications for UGEC 3) What are the policy/practice implications of your research? Increasing the structural complexity of urban ecosystems may improve soil processes and the relative benefits (e.g. soil health), and possibly the overall resilience of these systems Humans alter the structure of the urban ecosystems in which they live and interact based on management practices, aesthetics and social- economical values Urban managers have the chance to liaise with citizens, ecologists, designers and architects to plan, design and maintain high- complexity urban ecosystems with enhanced ecosystem services

Implications for UGEC 4) What are the knowledge gaps and need for future research? Understand whether urban ecosystem simplification exerts a similar control on soil processes and biodiversity in different climates, soil types and socio-economical contexts Include a temporal dimension and the evaluation of ecosystem legacies and the effects due to the age since land-use change Evaluate the relationship between urban ecosystem complexity and its resilience towards other drivers of change (e.g. climate change)

This research has been funded by the Australian Research Council (ARC LP ), the Australian Centre for Urban Ecology (ARCUE), AGCSA and the Frank Keenan Trust Fund. AO is supported by MIFRS and MIRS scholarships. More info about my research are available at: