黄土高原油松根际土壤酶活性及真菌群落多样性研究——以黄龙山林场为例

SOIL ENZYME ACTIVITY AND FUNGAL COMMUNITY DIVERSITY IN RHIZOSPHERE OF PINUS TABULAEFORMIS CARR. GROWING ON LOESS PLATEAU—A CASE STUDY OF HUANGLONGSHAN FOREST FARM

为了解黄土高原油松林根际土壤酶活性和真菌群落多样性,本研究分析了陕西黄龙县不同样区油松根际土壤脲酶、碱性磷酸酶、多酚氧化酶和过氧化氢酶活性,并采用巢式PCR-变性梯度凝胶电泳(PCR-DGGE)技术研究了油松根际土壤中真菌群落多样性。结果表明,该地区油松根际真菌群落相似性较高,但受坡向、海拔、土壤水分及人类扰动等诸多因素的影响,不同样区的真菌群落多样性和土壤酶活性存在差异。油松根际各土壤酶活性均表现出坡顶样地高于坡底样地,阴面样地高于阳面样地,林区路旁样地由于采样环境不同于林中样地,酶活性介于其他样地之间;丰富度(S)、Shannon-Wiener指数(H)、Simpson指数(D)、均匀度指数(EH)分析表明,该区域油松根际土壤真菌群落多样性分布特征与酶活性分布特征相一致。相关性分析表明,除过氧化氢酶外,其余酶活性之间、以及与真菌多样性均呈显著正相关(p<0.05);土壤含水量与真菌多样性和土壤酶活性除多酚氧化酶外均呈显著正相关(p<0.05);而土壤p H与各种酶活性之间均未达显著相关水平(p>0.05)。土壤含水量是影响该地区真菌群落多样性与土壤酶活性主要因素之一。

Chinese pine （Pious tabulaeformis Carr. ） is widely used as a pioneer tree species in the Loess Plateau of Northwest China for windbreak and sand-fixation, soil and water conservation thanks to its high tolerance of cold, drought and soil infertility and its liability of forming ectomycorrhiza. The formation of mycorrhiza has some important influences on soil enzyme activity and soil microbial community in the rhizosphere of the host plant. Rhizosphere refers to the interface between plant roots and soil, and is a complex and dynamic microecosystem developed in the process of plant growth. Study have shown that significant differences exist in rhizospheric soil microbial community between Chinese pines growing in different ecological condition. However, little has been so far reported on effects of the variations of soil properties and microbial distribution caused by the redistribution of soil properties and soil nutrients during the process of rainfall erosion on slope land on soil enzyme and mycorrhizal fungal community in the rhizosphere of pine trees. In order to understand soil enzyme activity and fungal community diversity in the rhizosphere of Chinese pine in the Huanglongshan Forest Farm, the nested PCR-DGGE （denaturing gradient gel electrophoresis） method was used to determine fungal community diversity at different slope positions in the forest farm, and relationships of fungal community diversity with activities of urease, alka- line phosphatase, polyphenoloxidase and hydrogenperoxidase, were investigated in an attempt to provide a theoretical basis for revealing interactions between vegetation, soil microbes and soil enzyme activity. Results show that all the soil enzymes displayed a trend declining down the slope in activity, and from shady slope to sunny slope. As sampling sites along the roadside differed in environment from those in the forest so the enzyme activities therein varied in-between those in the sampling sites located in the forest. Analysis of the samples for Richness, Shannon-Wiener index, Simpson index and Evenness indicates that fungal communities in the pine rhizospheric soils were quite high in similarity, but varied some- what in Richness （S） , Shannon-Wiener index （H） , Simpson index （D） and Evenness （E,） , suggesting that the fungi varied with slope position in species, biomass, diversity and functional diversity. The distribution of fungal diversity and the distribution of enzyme activity were quite similar in characteristic except for E,, both displaying a trend of declining down the slope and from shady slope to sunny slope, and the distributions in the sampling sites alongside roads ranged in- between those in the sampling sites in the forests However, the distribution of soil nutrients in slope land was quite differ- ent from that of pine rhizospheric microbial diversity and soil enzyme activity and characterized by losing from the slope and accumulating at the foot of the slope. The distribution of soil enzyme activity on slope is closely related to source and biological properties of soil enzymes, and microtopography and more likely to microecosphere of the rhizospheric microbes. Correlation analysis of fungal richness, soil enzyme activities, soil water content and soil pH shows that positive correla- tions existed between enzyme activities and fungal diversity （p 〈 0.05）, except for that of hydrogenperoxidase; between fungal diversity and soil water content （p 〈 0.05） ; between enzyme activities and soil water content （p 〈 0.05）, except for that of polyphenoloxidase; and between the enzymes per se in activity （p 〈 0. 05 ） , except for hydrogenperoxidase; but not between soil pH and enzyme activities （p 〉 0. 05）. All the findings indicate that in semi-arid regions, the higher the water content in the P. tabulaeformis rhizosphere, the higher the abundance of the fungi. Therefore, it can be concluded that soil water content is one of the major factors affecting soil enzvme activities and funsal community diversity in the soil.