https://doi.org/10.35662/unine-thesis-2781 University of Neuchâtel – Faculty of Sciences Institute of Biology Functional Ecology Laboratory Impacts of urban gardening on soil quality, soil fauna and soil multifunctionality PhD thesis Simon Tresch Thesis committee: Prof. tit. Claire Le Bayon (supervisor, Functional ecology laboratory, University of Neuchâtel) Dr. Andreas Fliessbach (co-supervisor, Department of Soil Sciences, FiBL) Dr. Marco Moretti (co-supervisor, Biodiversity and Nature Conservation, WSL) Prof. Sergio Rasmann (Functional ecology laboratory, University of Neuchâtel) Prof. Jérôme Cortet (CEFE, University Paul-Valéry Montpellier III) University of Neuchâtel 22/05/2019 Faculté des Sciences Secrétariat-décanat de Faculté Rue Emile-Argand 11 2000 Neuchâtel – Suisse Tél : + 41 (0)32 718 21 00 E-mail : [email protected] IMPRIMATUR POUR THESE DE DOCTORAT La Faculté des sciences de l'Université de Neuchâtel autorise l'impression de la présente thèse soutenue par Monsieur Simon TRESCH Titre: “Impacts of urban gardening on soil quality, soil fauna and soil multifunctionality” sur le rapport des membres du jury composé comme suit: • Prof. titulaire Claire Le Bayon, directrice de thèse, UniNE • Dr Andreas Fliessbach, co-directeur de thèse, FiBL, Soil Science, Frick • Dr Marco Moretti, co-directeur de thèse, WSL, Biodiversity & Conservation Biology, Birmensdorf • Prof. assistant Sergio Rasmann, UniNE • Prof. Jérôme Cortet, Université Paul Valéry, Montpellier, France Neuchâtel, le 15 juillet 2019 Le Doyen, Prof. P. Felber Imprimatur pour thèse de doctorat www.unine.ch/sciences Table of contents Page Preface V Abstract VII Résumé IX 1 General introduction1 1.1 Human impact on ecosystems....................................3 1.2 Urbanisation..............................................3 1.3 Urban ecosystems as novel ecosystems...............................4 1.3.1 Urban gardens........................................4 1.4 Soils and soil functions........................................5 1.4.1 Urban soils..........................................6 1.4.2 Urban soil functions.....................................8 1.5 Soil quality...............................................8 1.6 Urban gardening............................................8 1.7 Project BetterGardens .........................................9 1.8 Research gaps and overall research questions............................ 10 1.9 Study sites............................................... 10 2 Urban soil quality assessment 13 2.1 Introduction.............................................. 14 2.2 Material and Methods......................................... 14 2.2.1 Study sites and design.................................... 14 2.2.2 Physical soil quality indicators............................... 15 2.2.3 Chemical soil quality indicators............................... 15 2.2.4 Biological soil quality indicators............................... 15 2.2.5 Heavy metals......................................... 15 2.2.6 Statistics............................................ 17 2.3 Conclusion............................................... 17 2.4 Supplementary Tables and Figures.................................. 18 2.4.1 Supplementary Figures.................................... 18 2.4.2 Supplementary Tables.................................... 19 3 A gardener’s inuence on urban soil quality 29 3.1 Introduction.............................................. 30 3.2 Material and Methods......................................... 32 3.2.1 Study sites and design.................................... 32 3.2.2 Soil samples.......................................... 33 3.2.3 Measures of soil quality (MSQ)............................... 33 3.2.4 Explanatory variables.................................... 34 3.2.5 Soil functions......................................... 35 3.2.6 Soil quality indices...................................... 35 I 3.2.7 Multivariate soil quality assessment............................ 36 3.3 Results................................................. 37 3.3.1 Urban soil quality assessment................................ 37 3.3.2 Eects of garden management................................ 37 3.3.3 Eects of garden characteristics............................... 37 3.3.4 Eects of heavy metals.................................... 39 3.3.5 Dierences in functional groups of earthworms and decomposition........... 39 3.3.6 Soil quality indices...................................... 39 3.4 Discussion............................................... 40 3.4.1 Soil quality assessment.................................... 40 3.4.2 Eect of soil disturbance on urban garden soils...................... 41 3.4.3 Heavy metal assessement.................................. 41 3.4.4 Gardening eects on functional groups of earthworms and decomposition....... 42 3.4.5 Conclusion.......................................... 42 3.5 Supplementary Tables and Figures.................................. 45 3.5.1 Supplementary Figures.................................... 45 3.5.2 Supplementary Tables.................................... 54 4 Litter decomposition driven by soil fauna, plant diversity and soil management in urban gardens 69 4.1 Introduction.............................................. 71 4.2 Material and methods......................................... 73 4.2.1 Study area and site selection................................. 73 4.2.2 Litter decomposition experiment.............................. 74 4.2.3 Soil fauna........................................... 74 4.2.4 Environmental factors and management practices..................... 75 4.2.5 Data analysis......................................... 76 4.3 Results................................................. 78 4.3.1 Litter decomposition model................................. 78 4.3.2 Multilevel structural equation model............................ 78 4.3.3 Eects on litter residue quality............................... 79 4.4 Discussion............................................... 85 4.4.1 Soil fauna drives litter decomposition also in human dominated ecosystems...... 85 4.4.2 Garden land-use and management intensity aect decomposition mediated by soil fauna 85 4.4.3 Eects on litter residue quality............................... 86 4.4.4 Eects of garden land-use type and urban warming on litter decomposition...... 86 4.4.5 Study limitations and perspectives............................. 88 4.5 Conclusion............................................... 88 4.6 Supplementary Tables and Figures.................................. 89 4.6.1 Supplementary Figures.................................... 89 4.6.2 Supplementary Tables.................................... 100 5 Direct and indirect eects of urban gardening on aboveground and belowground diversity inuencing soil multifunctionality 113 5.1 Introduction.............................................. 114 5.2 Results................................................. 117 5.3 Discussion............................................... 119 5.4 Methods................................................ 121 5.5 Supplementary Tables and Figures.................................. 128 5.5.1 Supplementary Figures.................................... 128 5.5.2 Supplementary Tables.................................... 142 II 6 Discussion and Conclusion 153 6.1 General discussion........................................... 155 6.2 General conclusion and perspectives................................ 157 Bibliography 161 Acknowledgements 183 Curriculum Vitae 185 III Preface This dissertation is part of the interdisciplinary cial value of urban gardens in Switzerland and took project BetterGardens conducted at the Research In- place from January 2015 to December 2018. This stitute of Organic Agriculture FiBL and at the Swiss thesis is part of the subproject about soil quality, be- Federal Institute for Forest, Snow and Landscape Re- lowground diversity, and soil functions. It is con- search WSL nanced by the Swiss National Science ceptualised as a paper dissertation, meaning that all Foundation in the frame of the Sinergia programm main chapters are either published or submitted to (CRSII1_154416). The overall project aim was an in- scientic journals. Therefore, all rights of the main tegrated analysis of soil quality, biodiversity and so- chapters belong to the respective publishers. V Abstract Urban gardens are important and at the same again a main inuencing factor aecting soil func- time popular greenspaces. As urban areas are ex- tion decomposition and diversity of soil fauna species panding globally, urban gardens play an increasingly (earthworms, collembola, isopods and gastropods). important role in contributing to essential ecosys- We found a positive relationship of soil fauna species tem services, well-being of citizens, and biodiversity richness (4 taxonomic groups, 120 species and 81’007 in a city. Gardening activities determine above- and individuals) as well as plant species richness with de- belowground diversity of plants and insects. How- composition. This indicated that also in intensively ever, the eect of gardening activities on soil quality managed urban greenspaces, such as urban gardens, and soil functions have rarely been studied. For this biodiversity drives ecosystem services. purpose, a city-wide assessment of soil quality in- Furthermore, we assessed the impact of the three cluding key soil fauna species and soil functions was garden land-use types on soil fauna and multiple soil established on