Preliminary Study Of Fungal Hyphae Impacts On Soil Carbon And Fertility-related Parameters, As Well As Structure And Image Of Soil Colloids

Fungi contribute to a number of key ecosystem functions such as carbon cycling, nutrient mobilization from soil organic matter, nutrient mobilization from soil minerals, and linking trees through common mycorrhizal networks.Through field investigation, we found that the fungus habitat had closely connection with forest types.How to influence soil carbon sequestration, fertility and structural components during beneficial reaction between fungi and plants is the key in this paper. We concluded key points as following by study.1) Fungal hyphaes can secrete acidic phosphatase and acid protease, and these enzymes may promote the activation of ineffective organic P and N and enhance plant growth. Soil organic carbon accumulation and depletion of inorganic carbon could directly increase the extracellular enzyme secretions of all tested fungal hyphae, showing the function of hyphae in soil carbon sequestration and fertility. Lactarius deliciosus, Russula Integra and Gomphidius viscidus were able to excrete related P enzymes (acid phosphatase) and N (proteases) enzymes. In most cases, each enzymatic activity of these2enzymes were highest in2weeks culture in MMN medium.However, different fungus differed significantly in the enzyme activities, and G. viscidus had the lowest activity of acid phosphatase, but highest in protease activity. No significant differences were found in the other two fungus; Secondly, addition organic carbon (Humic acid, HA) and inorganic carbon (calcium carbonate) could significantly affect the activities of acid phosphatase and protease. When HA was added, activity of acid phosphatase steadily increased in3fungus, while fungus-specific patterns were found in protease activity, i.e., continuous increasing activity of protease in L. deliciosus protease were observed, while less HA-sensitivity were found in R. integra and G. viscidus; Thirdly, small amount of calcium carbonate addition could enhance the exudation of these two enzymes of acid phosphatase and protease, while addition more may reduce the enzymatic activities (e.g.,0.1g).2) Ectomycorrhizal fungi enhance the growth and fitness of plants resulting from it’s secretions could improve soil environment, and then influence soil caebon and fertility. However, the effects were different between dark brown forest soil and saline-alkali soil. For the good loam either from the surface or deep soils, the fungus treatment induced physical absorption of covering materials on colloid surface with non-significant increases in soil particle size (P>0.05). These increased the amount of variable functional groups (O-H stretching and bending, C-H stretching, C=O stretching, etc) by3-26%, and the crystallinity of variable soil minerals (kaolinite, hydromica, and quartz) by40-300%. However, the fungus treatment of saline-alkali soil obviously differed from the dark brown forest soil. There were12-35%decreases in most functional groups (O-H、Si-O-Si,COO-、carbonate),15-55%decreases in crystallinity of most soil minerals(except for quartz) but general increases in their grain size, and significant increases in soil particle size (P<0.05).These different responses sharply decreased element ratios (C:O, C:N, C:Si) in soil colloids from saline-alkali soil, moving them close to those of the good loam of dark brown forest soil.3) Fungi could secrete more extracellular enzymes about C, N and P effected on soil carbon, fertility and surface structures in the process of cultivation. As manifested by the significant differences in enzyme types and activities, our result clearly indicates that different fungi may function differently in soil C, N and P cycling, e.g., Russula Integra, Pholiota adipose, Gomphidiu rutilus and Geastrum mammosum secreted3-4types of extracellular enzymes with relative weak activities, while Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, Cyathus striatus and Lactarius deliciosus could secret>5enzymes with high activities. Moreover, significant correlations were found between chitinase and β-glucosidase (R=0.638), carboxymethyl cellulase and β-glucosidase (R=0.934), protease and polyphenol oxidase (R=0.752), and chitinase and laccase (R=-0.730), indicating possible inter-enzymatic cooperation among different fungi in soil nutrient cycling. In addition, this two kinds of fungi with high (C. striatus) and low(G rutilus) enzymatic activities were co-cultured by liquid and solid methods in dark brown soil revealed these inter-specific differences in enzymatic activity could affect functional groups, element composition and surface structure on soil colloids. The variable functional group traits such as O-H, N-H, C-H, C=O, COO-stretching decreased by11-60%, and co-culture with C. striatus reduced higher than with G. rutilus. However P=O, C-O stretching increased by9～22%, and the differences were not significant between the two fungi (P>0.05). The change of organic functional groups traits could directly result in the variation of the organic elementary compositions, but, the change between two fungi is not significant. These changes directly effected on the surface of soil colloids with physical absorption on and larger particle, but without significantly change between two fungi.