The Response Of Soil Microbial Community Structure To Cultivating Age, Fertilization And High Temperature In Tea Orchard

Tea(Camellia sinensis (L.) O. Kuntze) is an important cash crop in China. The accumulation of Al3+ and the serious acidification induced by tea plantation and chemical fertilizer make the soil in tea orchard a special habitat. At same time, climate change which induced the increased frequency of extreme high temperatures in summer will influence the soil microbial community structure. In order to have a deep knowledge of the soil microbial ecology in tea orchard and promote the sustainable development of tea plantation, it is important to study the response of soil microbial community structure in tea orchard to cultivating age, fertilization and high temperature.In this study, a series of field investigation and laboratory experiments were conducted based on the acid soil in tea orchard through qPCR, T-RFLP, Illumia MiSeq and other techniques, to make a inquiry on the difference of soil microbial community structure between the tea orchard and other agri-ecosystem, such as bamboo, forest and paddy field, and then, to study the effect of cultivating age, fertilization and high temperature on the soil microbial community structure and the abundance of genes related to nitrification and denitrification. The main research results are as follows:Compared to other agri-ecosystems, soil pH as well as the abundance of bacteria in tea orchard was lower, but the SOC was higher. The land use influenced the community structure of bacteria (Global R=0.997, P<0.01) and archaea (Global R=1, P<0.01) significantly. There were unique microorganisms and a higher microbial diversity in tea orchard. Correlation analysis indicated that the bacterial and archaeal diversity indices were negatively correlated to the ratio of C to N and soil pH respectively (P<0.01). Overall, the higher soil nutrients and microbial diversity in tea orchard made the tea cultivation a sustainable land use of red soil.The composition and abundance of bacterial and fungal communities in tea orchard soils with various stand ages, namely,8 (Y8),20 (Y20),34 (Y34) and 56 years (Y56), and in acidic forest soil were analyzed using the Illumina MiSeq sequencing platform and qPCR. The abundance of soil bacteria and fungi in tea orchards was significantly higher in younger tea orchards (Y8 and Y20). The similar structure of bacterial and fungal communities in Y34 and Y56 tea orchard, which was different from that in Y8 and Y20 tea orchard, indicated a relatively stable structure of microbial community in older tea orchard.Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Gemmatimonadetes and Firmicutes were the major bacteria in tea orchard soil. Proteobacteria accounted for 50% of all phyla. Ascomycota and Basidiomycota represented 90% of the fungal communities in soil, Ascomycota occupied 42.67%-67.37% of the fungal communities in tea orchard soil. From the younger tea orchard to older tea orchard, the succession of soil microbial community was. in the following order:Acidobacteria, Actinobacteria, Chloroylexi and Ascomycota were more abundant, while Proteobacteria and Bacteroidetes accounted for less in older tea orchard.A field experiment involving organic fertilizer (OF), chemical fertilizer (CF), and an unfertilized control (CK) treatment was arranged to analyze the temporal changes in the bacterial and archaeal communities at bimonthly intervals based on the 16S rRNA gene using T-RFLP profiling. The abundance of total bacteria, total archaea and selected functional genes (bacterial and archaeal amoA, bacterial narG, nirK, nirS, and nosZ) was determined by qPCR. The results indicated that the bacterial and archaeal community structures varied significantly (P<0.01) with season and fertilization based on changes in the relative abundance of dominant T-RFs. The soil temperature significantly affected the bacterial and archaeal community structures (P <0.01). The abundance of the detected genes changed seasonally. The total bacteria, total archaea, and archaeal amoA were less abundant in July. The bacterial amoA and denitrifying genes, except for the nirK gene, were less abundant in September. In general, Organic fertilizer increased the soil nutrients and the abundance of the observed genes, and thus improve the soil environment in tea orchard, while the CF treatment had little influence on the abundance of the observed genes. Of the soil chemical properties, soil organic carbon was the most important factor and was significantly correlated with the abundance of the detected genes (P<0.05), except for the nirK and archaeal amoA gene.An incubation experiment where the soil was taken from a tea field, involving two temperatures (25℃ and 35℃) and three levels of water saturation (30%,55% and 80% water-filled pore space (WFPS)) was conducted. The abundance of the three microbial domains (bacteria, archaea and fungi) and functional genes related to the transformation of nitrogen were studied by qPCR. The response of microbial communities to different treatments were monitored by T-RFLP. High temperature limited the transformation of ammonium to nitrate, increased the pH and reduced all analyzed genes except for the fungal marker genes (ITS) at 30% and 55% WFPS. However, at 80% WFPS, all genes at 35℃, except bacterial amoA, increased and exceeded their abundance at 25℃ at the end of incubation. High temperature and soil moisture significantly (P<0.01) influenced the community structure of all three domains through changing the relative abundance of dominant T-RFs or selecting new dominant T-RFs. The response of all three domains to temperature and different water regimes was also influenced by the incubation time (P<0.01).