Michele E. D’Amico Soil ecology and pedogenesis on ophiolitic materials in the western Alps (Mont Avic Natural Park, North-western Italy): soil properties and their relationships with substrate, vegetation and biological activity. Università degli Studi di Milano Bicocca Dottorato di Ricerca in Scienze Ambientali XXII ciclo Novembre 2009 2 Michele E. D’Amico Soil ecology and pedogenesis on ophiolitic materials in the western Alps (Mont Avic Natural Park, North-western Italy): soil properties and their relationships with substrate, vegetation and biological activity. Tutor: Prof Franco Previtali Università degli Studi di Milano Bicocca Dottorato di Ricerca in Scienze Ambientali XXII ciclo Novembre 2009 3 Summary Abstract ................................................................................................................................................ 7 Acknowledgements .............................................................................................................................. 8 1 – Introduction .................................................................................................................................... 9 1.1 Why studying soils on ophiolites: the “serpentine factor” ......................................................... 9 1.2 Plant-soil relationships: the ecology of soils formed on serpentinite ...................................... 10 1.3 Soil forming processes on ultramafic materials ....................................................................... 11 1.4 The study area .......................................................................................................................... 13 1.5 Aims and structure. .................................................................................................................. 14 References ...................................................................................................................................... 14 2. Edaphic influences on vegetation of ophiolitic substrates ............................................................. 17 Abstract .......................................................................................................................................... 17 2.1. Introduction ............................................................................................................................. 17 2.2. Materials and methods ............................................................................................................ 18 2.2.1. Field data collection and soil sampling ............................................................................ 18 2.2.2. Laboratory analysis .......................................................................................................... 18 2.2.3. Data analysis .................................................................................................................... 19 2.3. Results ..................................................................................................................................... 20 2.3.1. The vegetation .................................................................................................................. 20 2.3.2. The soils ........................................................................................................................... 21 2.3.3. Soil-vegetation relationships ............................................................................................ 22 2.3.4. Notes on some species ..................................................................................................... 23 2.4. Discussion ............................................................................................................................... 23 2.4.1. Forest habitats .................................................................................................................. 23 2.4.2. Alpine habitats ................................................................................................................. 25 2.5. Conclusions ............................................................................................................................. 26 References ...................................................................................................................................... 27 3. Podzolization over ophiolitic materials .......................................................................................... 34 Abstract .......................................................................................................................................... 34 3.1. Introduction ............................................................................................................................. 34 3.2. Physiographic outlines of the study area................................................................................. 35 3.3. Materials and methods ............................................................................................................ 35 3.3.1. Soil description and sampling .......................................................................................... 35 3.3.2. Laboratory analyses: soil chemistry and spodic properties ............................................. 35 3.3.3. Laboratory analyses: soil mineralogy and parent material .............................................. 36 3.4. Results and discussion ............................................................................................................ 36 3.4.1. Parent material ................................................................................................................. 36 3.4.2. Morphological and physical properties of soil profiles ................................................... 37 3.4.3. Humus forms .................................................................................................................... 38 3.4.4. Chemical properties ......................................................................................................... 38 3.4.5. Bulk chemical composition .............................................................................................. 38 3.4.6. Extractable forms of Fe, Al and Si and their meaning (Table 3.8) .................................. 39 3.4.7. Spodicity indexes ............................................................................................................. 40 3.4.8. Soil classification ............................................................................................................. 41 5. Conclusions ................................................................................................................................ 41 References ...................................................................................................................................... 43 4: Podzolization over ophiolitic materials: weathering and clay minerals ........................................ 51 Abstract .......................................................................................................................................... 51 4.1. Introduction ............................................................................................................................. 51 4 4.2 Materials and methods ............................................................................................................. 52 4.3 Results ...................................................................................................................................... 53 4.3.1 Parent material .................................................................................................................. 53 4.3.2 Mass transport calculations ............................................................................................... 54 4.3.3 Granulometric evolution ................................................................................................... 55 4.3.4 Clay minerals .................................................................................................................... 55 4.3.5 Magnetic minerals ............................................................................................................. 56 4.3.6 Allophanic materials ......................................................................................................... 57 4.3.8: IR measurements .............................................................................................................. 57 4.4 Discussion and conclusions ..................................................................................................... 58 Bibliography................................................................................................................................... 60 5. Heavy metal speciation and mobility along altitudinal gradients on ophiolites. ........................... 69 Abstract .......................................................................................................................................... 69 5.1 Introduction .............................................................................................................................. 69 5.2 The studied soil profiles ........................................................................................................... 70 5.3 Materials and methods ....................................................................................................... 71 5.4 Results ...............................................................................................................................