Effects Of Long-term Fertilization And Plastic Film Mulching On Soil Microbial Diversities In Brown Earth

The soil microbial diversity is an important indicator of soil changes caused by natural and artificial interference. Therefore, it is necessary to elucidate the functions of microbial communities in different environments and the influence of their structural and functional alterations in the ecosystems. The turnover process of dominanted nutrient metabolism and community properties of in-situ soil microbe needs to be clarified from long-term fertilization experiment. Many researches have been carried on the soil fertility in the long-term fertilization and plastic film mulching experiment station of brown earth at Shenyang Agricultural University (established in 1987), which showed that the physicochemical and biological properties changed by long-term fertilization and plastic film mulching. However, due to the technique limitation in the past time, some results obtained before could not exactly reflect the soil microorganisms’information, and it is not clear about the responses of microbial community structure and diversity to different fertilizer and mulching, and also the coupling of them. Base on the previous works, the techniques of fluorescence real-time quantitative PCR and next-generation 454 high-throughput DNA sequencing have been used to qualitative and quantitative analysis of different fertilization and plastic-film mulching on soil microbial diversity. By adopting technique of DNA-based stable carbon isotope probing (13C-DNA-SIP), the complex environment microbial community physiological functions will be conducted to study under conditions of fertilization and plastic-film mulching in order to determine the microbial function populations under certain condition, and to study the differences of soil microbial function diversity among treatments. The main results are as follows:(1) The soil microbial diversity index declined by long-term inorganic fertilizer regardless of mulching or not, and the microbial community structure changed by fertilizer and mulching. At phylum level, under mulching condition, the relative abundances of Firmicutes of no fertilizer (CK), nitrogen fertilizer (N), nitrogen and phosphrous fertilizer (NP), manure (M) and organic and NP fertilizer (MNP) were increased. Compared with CK, relative abundances of’Chloroflexi and Firmicutes in fertilizer treatments were increased respectively under no mulching and mulching condition, while the relative abundance of Actinobacteria, Armatimonadetes and Crenarchaeota were decreased regardless of mulching or not. At genus level, compared with CK, the relative abundance of Nitrospira and Clostridium were increased respectively in inorganic fertilizer (N and NP) and in organic fertilizer (M and MNP). Overall, dominant microorganisms population were suppressed and inferior microorganisms population were promoted in fertilizer treatments. pH, total carbon, total nitrogen, and microbial biomass were the main influencing factors of soil microbial community structure.(2) The abundances of Bacterial were increased significantly in organic treatments (M and MNP), while decreased in inorganic treatment (N and NP). The abundance of Crenarchaeota and ammonia-oxidizing archaea (AOA) were descended in fertilizer treatments, especially in inorganic fertilizer (N and NP), while the ammonia-oxidzing bacteria (AOB) were promoted in organic fertilizers (M and MNP). There was a positive correlation (p<0.05) between Bacterial, Crenarchaeota, AOA and AOB with pH. Total carbon was the main factor affecting the Bacterial and AOB. while it was negative correlation (p<0.01) between Bacterial, Crenarchaeota and AOB with NH4+-N and NO3--N.(3) The results of 13C-DNA-SIP showed that the Proteobacteria and Actinobacteria were the mostly dominant active microorganisms in four treatments of CK, NP, M and MNP under phylum level. The relative abundance of Gemmatimonadetes and Firmicutes were promoted in CK, the same to Proteobacteria in NP and MNP and to Acidobacteria and Gemmatimonadetes in M. At genus level, the mostly dominant active microorganisms in each treatment included Gemmatimonadetes, Marmoricola and Nitrospira in CK, Actinospica, Catenulispora, Rhodanobacter and Pseudomonas in NP, Gp6, Gp10, Gemmatimonadetes and Steroidobacter in M, Gp6, Marmoricola and Nitrospira in MNP. The relative abundance of Arthrobacter and Gemmatimonas were promoted by mulching, and it was significant to Nitrospira in CK and M.