HUNGARIAN UNIVERSITY OF AGRICULTURE AND LIFE SCIENCES DOCTORAL SCHOOL OF BIOLOGICAL SCIENCES DOCTORAL (PH.D) DISSERTATION RESPONSES OF SOIL CO2 EFFLUX TO BIOTIC AND ABIOTIC DRIVERS IN AGRICULTURAL SOILS BY MALEK INSAF GÖDÖLLŐ 2021 Title: Responses of soil CO2 efflux to biotic and abiotic drivers in agricultural soils Discipline: Biological Sciences Name of Doctoral School: Doctoral School of Biological Sciences Head: Prof. Dr. Zoltán Nagy Department of Plant Physiology and Plant Ecology Institute of Agronomy Hungarian University of Agriculture and Life Sciences, Supervisor 1: Dr: János Balogh, Department of Plant Physiology and Plant Ecology Institute of Agronomy Hungarian University of Agriculture and Life Sciences, Supervisor 2: Prof. Dr. Katalin Andrea Posta Department of Microbiology and Microbial Biotechnology Institute of Genetics and Biotechnology Hungarian University of Agriculture and Life Sciences, ..................................................... ................................................. Approval of Head of Doctoral School Approval of Supervisors TABLE OF CONTENT 1. Introduction: .......................................................................................................................... 1 1.1. Foreword ......................................................................................................................... 1 1.2. Objectives ........................................................................................................................ 3 2. LITERATURE REVIEW ..................................................................................................... 4 2.1. Climate change ................................................................................................................ 4 2.2. Greenhouse Gases (GHGS) emissions ............................................................................. 4 2.2.1 Summary of national emissions and removal related trends in Hungary .................... 5 2.2.2 The latest concentrations and GWP of the three GHGs (CO2, CH4 and N2O) ........... 5 2.3. Overview of sources and sinks of carbon dioxide efflux ................................................ 6 2.3.1 Sources of carbon dioxide efflux ................................................................................ 6 2.3.1.1 Soil respiration (Rs) and its components ............................................................. 9 2.3.2 Sinks of Carbon dioxide efflux ................................................................................. 11 2.3.2.1 Photosynthesis and phloem transport ................................................................ 11 2.4. Factors affecting soil CO2 efflux ................................................................................... 15 2.4.1 Environmental factors ............................................................................................... 15 2.4.1.1 The effect of soil temperature on CO2 emissions .............................................. 15 2.4.1.2 The effect of low soil temperature on CO2 emissions (freezing) ...................... 17 2.4.1.3 The effect of soil water content on CO2 emissions ........................................... 18 2.4.1.4 Relationship between soil moisture and Rs ....................................................... 19 2.4.2 Biotic factors ............................................................................................................. 20 2.4.2.1 Photosynthesis ................................................................................................... 20 2.4.2.2 Fires ................................................................................................................... 21 2.4.3 Effect of agricultural management practices on soil respiration ............................... 21 2.4.3.1 N fertilization .................................................................................................... 22 2.4.3.2 Tillage application ............................................................................................. 23 2.4.3.3 Irrigation ............................................................................................................ 25 2.4.3.4 Effects of plant residue and land-use change on soil GHG emissions .............. 25 2.4.4 Soil properties ........................................................................................................... 26 2.4.4.1 Soil organic matter content ............................................................................... 26 2.4.4.2 Soil pH-values ................................................................................................... 27 2.4.4.3 Nutrients ............................................................................................................ 27 2.4.4.4 Soil pore space and soil texture ......................................................................... 28 2.5. Measurement techniques used to quantify the GHGs emissions from soils ................. 29 2.5.1 Chamber systems ....................................................................................................... 29 2.5.1.1 Closed chambers ............................................................................................... 32 2.5.1.2 Open chambers .................................................................................................. 33 2.5.2 Data evaluation .......................................................................................................... 34 2.5.3 Laboratory experiments on soil CO2 efflux .............................................................. 34 2.5.4 Micro-meteorological methods ................................................................................. 35 2.5.5 Continuous monitoring .............................................................................................. 36 2.5.6 Spatial measurements ................................................................................................ 37 2.6. Strategies for GHG emissions mitigation in agriculture ............................................... 38 2.6.1 Cropland management ............................................................................................... 39 2.6.1.1 Agronomy .......................................................................................................... 40 2.6.1.2 Tillage/residue management ............................................................................. 40 2.6.1.3 Nutrient management ........................................................................................ 40 2.6.1.4 Water management ............................................................................................ 40 2.6.1.5 Land cover (use) change ................................................................................... 41 2.6.2 Management of grazing land and pasture improvement ........................................... 41 2.6.2.1 Grazing intensity ............................................................................................... 41 2.6.2.2 Augment productivity (including fertilization) and species introduction ......... 41 2.6.3 Management of organic soils .................................................................................... 41 2.6.4 Restoration of degraded lands ................................................................................... 42 3. Material and Methods ......................................................................................................... 43 3.1. Field measurements ....................................................................................................... 43 3.1.1 Site description .......................................................................................................... 43 3.1.2 Field design and soil CO2 exchange measurements .................................................. 44 3.1.3 Additional measurements .......................................................................................... 46 3.2. Soil characteristics analysis ........................................................................................... 47 3.3. Lab measurements ......................................................................................................... 47 3.3.1 Sampling of soil ........................................................................................................ 47 3.3.2 Lab design and soil CO2 exchange measurements .................................................... 49 Three successive laboratory experiments using the different treatments (SWC and N fertilization) in the presence and absence of plant were carried out in the following order: ........................................................................................................................................... 49 3.3.2.1 Experiment 1: .................................................................................................... 49 3.3.2.2 Experiment 2: .................................................................................................... 49 3.3.2.3 Experiment 3: .................................................................................................... 50 3.3.3 Cumulative gas effluxes ............................................................................................ 51 3.4. Microbiological method used ........................................................................................ 51 3.4.1 Classical method ......................................................................................................