drivers of soil respiration of root and microbial ... - Unitus DSpace

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3.2.4. Data analyses and definition of terms…………………….………………….74
3.2.5.Time lag by mesh-bag technique…...…………………………….……..…….75
3.3. Results…………………………………………………………………………...…….76
3.3.1. Raw isotopic values………………………………….……….…….….……..76
3.3.2. Label partitioning……………………………………….………………..…..76
3.3.3. Mean Residence Time………………………………………………………..78
3.3.4. Mean Age of new C……………………………………………………….….79
3.3.5. Time lag by mesh bag technique………………………………………….….79
3.4. Discussion……………………………………………………………………………...82
3.4.1. Speed of C cycling……………………………………………………………82
3.4.2. Allocation patterns……………………………………..………………….…84
3.4.3. Destructive vs. Non-destructive technique……………………..…………….85
4. THE EFFCT OF DEFOLIATION MANAGEMENT PRACTISES ON SOIL
RESPIRATION OF DIFFERENT ORIGIN AND SOIL BIOCHEMICAL
PROPERTIES……………………………………………………………………………………...90
4.1. Introduction……………………………………………………………….………..…91
4.2. Materials and Methods……………………………………………………………….92
4.2.1. Research area and experimental design…………………….……………….92
4.2.2. Soil respiration and partitioning……………………………….……….……93
4.2.3. Soil chemical and biochemical properties …………………………..………95
4.3. Results………………………………………………………………….………………98
4.3.1. Soil respiration and partitioning……………………….………………….…98
4.3.2. Soil biochemical properties …………………………………………….…..104
4.4. Discussion…………………………………………………………..……….………..110
4.4.1. Soil respiration and defoliation……………………………...……….……..110
4.4.2. Microbial activity and defoliation……………………….………….………112
4.4.3. Conclusions………………………………………….………….…………..114
5. FOCUSING ON ROOT-DERIVED RESPIRATION: C COSTS OF NITRATE
REDUCTION AS ESTIMATED BY 14 CO2 LABELING OF LUPINE AND CORN……......121
5.1. Introduction………………………………………………………………………….122
5.2. Materials and methods…………………………………………………….………..124
5.2.1. Soil……………………..………………………………………………..…..124
5.2.2. Plants and growth conditions……………………………………………….124
5.2.3. 14 C labeling and 15 N application……………………………………..……..125