内生真菌对高寒草地紫花针茅凋落物分解的影响

Effect of Epichloёendophyte on the litter decomposition of Stipa purpurea in alpine grassland

禾草内生真菌对于提高宿主植物对生物和非生物胁迫的耐性发挥着积极作用,然而,禾草内生真菌共生体凋落物分解对于草地生态系统养分循环的影响仍不清楚。本研究以紫花针茅为研究对象,比较带内生真菌(E+)与不带内生真菌(E-)植株凋落物分解过程中重量及全氮、木质素和纤维素含量,以及木质素∶N、纤维素∶N与全氮、木质素和纤维素残留率的变化,以期揭示内生真菌在紫花针茅凋落物分解过程中发挥的作用。主要结果如下:E+紫花针茅凋落物分解速率高于E-,具有更短的分解周期;随着时间的延长,紫花针茅凋落物木质素含量和木质素∶N由E+显著高于E-逐渐变为二者之间差异不显著,纤维素含量、纤维素∶N和纤维素残留率则逐渐变为E+显著低于E-;另外,随着分解时间延长,E+和E-凋落物全氮含量呈上升趋势,而全氮残留率呈现出下降-上升-下降的趋势,且后期E+显著低于E-。因此,内生真菌不同程度地促进了紫花针茅凋落物全氮、木质素和纤维素的降解。

Grass fungal endophytes can positively improve the tolerance of their host plant to biotic and abiotic stress.However,the effect of the symbiotic fungal endophyte on grass host litter decomposition on the nutrient cycling of grassland ecosystem is not clear.In this research a detailed comparison was made between litter of Stipa purpurea with endophyte(E+)and without endophyte(E-).Analyses performed included weight of litter shed,contents of total nitrogen,lignin and cellulose,change in lignin∶N and cellulose∶N ratios and residual concentrations of total N,lignin and cellulose in E+and E-litter samples.The results were as follows:E+S.purpurea litter had a higher decomposition rate and a shorter decomposition cycle than E-litter.With increase in the decomposition time,the content of lignin and the ratio of lignin∶N in S.purpurea litter changed gradually from higher in E+than E-,to there being no significant difference between E+and E-litter.The cellulose content,cellulose∶N ratio and cellulose residual concentration in E+S.purpurea litter were significantly lower than E-litter in the latter part of the decomposition cycle.In contrast,the total N content of S.purpurea litter displayed a rising trend,and the elemental N residual concentration displayed a declining-rising-declining trend as decomposition progressed.E+S.purpurea litter had a lower residual N content than E-litter in the later stages of decomposition.Hence,the presence of fungal endophyte enhanced,to different degrees,the rate of degradation of leaf mass,total N,lignin and cellulose in S.purpurea litter.