Effects Of Arbuscular Mycorrhizal Fungi On The Decomposition Of Organic Matter

Arbuscular mycorrhizal fungi (AMF), one of the most important soil symbiotic microbes, can form symbiosis with over 80% terrestrial plants. On one hand, host plants provide carbon sources for AMF. On the other hand, AMF acquire nutrients from soils for host plants. As AMF are obligate symboints that acquire carbon nutrition only from host plants, questions arise:do and how AMF affect soil organic matter (SOM) decomposition? I hypothesize that AMF facilitate SOM decomposition through enhancing nutrient acquisition from organic matter under nutrient deficient e.g. low phosphorus soil. To address this hypothesis, I employed dual 15N/13C labeling technique to quantify the organic decomposition rate under three P levels. I also compared the effect of legume Medicago sativa L. and non-legume Plantago depressa L. on SOM decomposition. I used PCR-DGGE technique to analyze bacteria communities and tested soil phosphatase activity. The results are as follows:1 The effect of AMF on SOM decomposition under different soil P levelsAMF colonization rate decreased significantly as soil P levels increased. Under low soil P, AMF increased biomass and 15N content of the host plant Medicago sativa L., but decreased organic N, C content in the decomposing bags, indicating that AMF promoted SOM decomposition.2 The effect of legume and non-legume plants on SOM decompositionCompared to legume plant M. sativa, non-legume P. depressa increased 15N cont-ent in shoots, but decreased organic N, C content in the decomposing bags. AMF did not reduce organic N and C content significantly under M. sativa, but AMF reduced organic N, C content significantly under P. depressa.3 The effect of AMF on soil bacteria communitiesAMF changed soil bacteria communities. In alkaline soil condition, AMF reduced ACP activity, but increased ALP activity significantly.