The Effects of Temperature, Moisture, and Management on Soil Microbial Properties in Two Different Soils.

Climate change is one of the most pressing current issues with great potential to affect agricultural practices and capabilities. Of particular need for greater understanding is the potential of natural feedback loops to climate change.  The potential loss of soil carbon due to warming is a major feedback loop. In order to understand this process, it is crucial to understand the processes by which soil carbon is stored and released. In Mollisols, this process is largely mediated by soil macroaggregates which are generally correlated with soil microbial population – particular that of soil fungi. In Oxisols, this process is more related to the stability of organo-mineral complexes formed from metal oxides (particularly Al and Fe). As part of a collaborative, on-going, incubation study, this project aims to explore the various biological, chemical, and physical factors that affect soil carbon storage and release. This portion of the project has more specific aims; primarily to look more strictly at the biological controls of these soil C processes. The incubation experiment used a factorial design with four factors. The treatments were: soil type, temperature regime, moisture regime, and aggregation. The soil type treatment (4 levels) consisted of four soils: Oxisol/No-till, Oxisol/Tilled, Mollisol/No-Till, and Mollisol/Tilled. The temperature treatments (3 levels) consisted of 12°C, 24°C, and 36°C. The moisture treatments (2 levels) consisted of field capacity and 80% of field capacity.  The aggregate treatments (2 levels) consisted of <4mm sieved (preserved macroaggregates) and <4mm aggregates ground to <0.25mm and sieved (destroyed macroaggregates). The point of these treatments is look more in depth at specific aspects of soil carbon storage/cycling, such as microbial activity level (temperature and moisture) or physical aggregate protection (aggregation). This part of the study is focusing on changes to microbial population and community structure which is determined with Phospholipid and Fatty Acid Analysis (PLFA). Statistical analysis is being done using R 3.14. Of particular interest are the effects on the ratio of bacteria to fungi and the effects the ratio of gram positive to gram negative bacteria. Soil fungi in Mollisols are known to be important in soil aggregation formation and thus carbon storage. Gram positive bacteria have different metabolism compared to that of gram negative bacteria; which has the potential to affect soil C dynamics. The ultimate desired outcome of this study is to improve our understanding of soil carbon dynamics; both to improve understanding of climate change and to be able to make better land-management recommendations for improving soil C sequestration.