Nitrogen controls spatial and temporal variability of substrate-induced respiration curves within six years of bare fallow
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| Titles: | Main Title: Nitrogen controls spatial and temporal variability of substrate-induced respiration curves within six years of bare fallow Subtitle: First Semi-Annual Progress Report |
| Description: | Abstract: Nitrogen (N) contents in soil are globally increasing because of anthropogenic inputs or decreasing due to soil degradation. Yet, little is known on the role of N in microbial activity and related soil organic carbon (SOC) mineralization. Two common theories, the stoichiometric decomposition and the microbial nitrogen mining theory, predict contrasting effects of N availability. We propose that microbial responses to nitrogen availability can be studied by measuring substrate-induced respiration (SIR) in soils under decreasing soil organic matter (SOM) supply, i.e. on a field under 7 years of bare fallow. We hypothesized that microbes maintain their activity and ability to mineralize C, due to microbial N mining. To test this hypothesis, we investigated spatial and temporal patterns of SIR on a field after 1, 3, and 7 years of bare fallow. The analyses comprised the contents of SOC, mineral nitrogen (Nmin), particulate organic matter (POM), texture, as well as several SIR fitting parameters (e.g. basal respiration rate, microbial biomass C, microbial growth rates, peak respiration rates, total CO2 release) each with and without additions of mineral N. We traced the source of CO2 that evolved during SIR (sugar vs. SOC-derived CO2) by conducting 13C-labelling experiments. Further hints on the N mining theory were gathered by repeated sugar additions. The results showed that most SIR parameters like basal respiration, microbial biomass, and growth rates did not consistently correlate with Nmin, and neither with SOC, POM, or texture. However, the shape of the SIR curves changed with prolonged bare fallow: The maximum respiration rate during the exponential growth phase declined by 47% but soils often developed a second growth phase. When also N was added to the samples, SIR curves of the 1st and 7th year of fallow were similar and showed a high first growth phase and no second peak. A similar curve was also observed after repeated sugar additions but without N supply. The proportion of sugar- and SOM-derived CO2 varied in the course of SIR and between fertilized and non-fertilized treatments. We conclude that the first peak shows the amounts of immediately available nitrogen while the second growth phase indicates delayed CO2 release due to N mining from refractory SOM. Hence, there was no significant decrease of total CO2 evolution during SIR with proceeding time of fallow. |
Responsible Party
| Creator: | Nele Meyer (Author) |
| Publisher: | CRC/TR32 Database (TR32DB) |
| Publication Year: | 2015 |
Topic
| TR32 Topic: | Soil |
| Related Subproject: | B3 |
| Subjects: | Keywords: Bare Soil, CO2, Soil Respiration, soil Heterogeneity |
File Details
| Filename: | Report_NeleMeyer.docx |
| Data Type: | Text - Text |
| Size: | 32 Pages |
| File Size: | 3.4 MB |
| Date: | Available: 30.09.2014 |
| Mime Type: | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| Data Format: | MS word (2007) |
| Language: | English |
| Status: | Completed |
Constraints
| Download Permission: | Only Project Members |
| General Access and Use Conditions: | According to the TR32DB data policy agreement. |
| Access Limitations: | According to the TR32DB data policy agreement. |
| Licence: | [TR32DB] Data policy agreement |
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Specific Information - Report
| Report Date: | 30th of September, 2014 |
| Report Type: | PhD Report |
| Report City: | Bonn, Germany |
| Report Institution: | Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology |
| Volume: | 1 |
| Number of Pages: | 32 (1 - 32) |
Metadata Details
| Metadata Creator: | Nele Meyer |
| Metadata Created: | 09.10.2015 |
| Metadata Last Updated: | 09.10.2015 |
| Subproject: | B3 |
| Funding Phase: | 3 |
| Metadata Language: | English |
| Metadata Version: | V50 |
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| Metadata Downloads: | 0 |
| Dataset Downloads: | 3 |
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