放牧对不同径级胡杨根际土壤真菌群落代谢特征的影响

Grazing affected metabolic characteristics of rhizospheric fungi community of Populus euphratica Oliv. with different diameters

放牧是干旱区主要的人类干扰活动,对土壤微生物的结构和组成具有重要影响。分析放牧对干旱区胡杨绿洲土壤真菌群落功能性质的影响对认识干旱区元素循环和生态系统维持与稳定具有重要意义。在额济纳胡杨林绿洲,依据胡杨林放牧差异(牲畜的数量、放牧频率)选取3个放牧强度样地:重度放牧(heavy grazing,HG)、中度放牧(moderate grazing,MG)和轻度放牧(light grazing,LG);设置A(胸径:0～10 cm)、B(胸径:10～20 cm)、C(胸径:20～30 cm)、D(胸径:30～40 cm)和E(胸径:>40 cm) 5个胡杨径级,采用Biolog-FF微平板方法分析真菌群落代谢特征。结果表明:胡杨径级对其根际真菌群落代谢活性具有显著影响,解释率为7.8%;根际真菌群落代谢活性随放牧强度的增加而减弱(AWCD_(LG)>AWCD_(MG)>AWCD_(HG));轻度放牧情况下,胡杨径级对真菌群落代谢活性不具有显著影响,而在中度和重度放牧下,不同径级胡杨根际真菌群落代谢活性之间具有显著性差异,说明放牧对不同径级胡杨具有不同影响,从而导致其根际真菌群落代谢活性的差异性响应;放牧和胡杨径级对胡杨根际真菌群落的总碳源利用率和各分类碳源利用率均不具有交互作用,但对功能多样性指数具有交互影响,表明各径级下,不同放牧强度没有改变真菌的整体代谢强度,但改变了真菌群落的组成结构;此外,放牧强度和径级大小主要是通过改变利用小分子碳源的真菌而影响真菌群落代谢特征的。

Grazing is one of the most important anthropogenic activities in drylands,which could influence the structure and components of soil microbial community.It is critical to understand the effects of grazing on metabolic characteristics of fungi community that is closely related with nutrient cycling and ecosystem stability in drylands.We selected three levels of grazing intensity:heavy grazing(HG),moderate grazing(MG)and light grazing(LG).We set five diameter classes of trees[A(0-10 cm),B(10-20 cm),C(20-30 cm),D(30-40 cm)and E(>40 cm)]with each grazing level in Ejina Oasis to explore metabolic characteristics and diversity of rhizospheric fungi community in Populus euphratica Oliv.forest by Biolog-FF micro-plate.The results showed that diameter class size had significant effect on fungi community metabolism,accounting for 7.8%of variance.The fungi community metabolic activities gradually decreased along with increasing grazing intensity(AWCDLG>AWCDMG>AWCDHG).There was no obvious difference under different diameter classes in LG site while significant differences were observed in MG and HG site.This result indicated that the effects of grazing intensity on P.euphratica were dependent on tree diameters,thus leading to diverse responses of fungi community.While there was no interactive effect between grazing intensity and diameter on metabolic activities of fungi community but they interacted to affect diversity,indicating that grazing intensity didn’t change the metabolic intensity of fungi community but changed the community structure.In addition,the effects of grazing intensity and diameter class of trees on fungi community metabolic characteristics were mainly due to alteration of fungi principally using the small molecular carbon sources.