杉木和香樟酸雨酸解底物的分解格局

摘要

采用凋落物分解袋法,选取湘西地区两种人工林优势树种(香樟和杉木)的凋落叶作为分解材料,分析了两种凋落叶经酸解处理后凋落物分解及其微生物活性的变化.结果表明:酸解处理过程会使两种凋落叶损失一定的质量,随着酸解强度的增加质量损失增加,且酸解处理对香樟凋落物质量损失的影响较杉木凋落物大.不同物种凋落物对酸解强度的差异性反应产生了后续分解过程的差异格局:酸雨酸解作用的增强抑制了杉木凋落物分解过程中包括真菌生物量以及纤维素酶与木质素酶在内的微生物活性;而对于香樟凋落物分解过程,微生物活性对酸雨酸解的响应因变量不同、分解期不同而存在差异性.两物种凋落物的总失重率、木质素和纤维素分解率对酸解作用的响应及其在不同分解期的表现也存在差异性:对于杉木凋落物,在分解前期其失重率表现为T1 ＞T2＞T3,而在后期随酸解强度的增大而升高,即T3＞T2/T1;香樟凋落物在分解的前期(T1＜T2＜T3)与后期(T1＞T2＞T3)情况则正好与杉木凋落物相反.总之,酸雨酸解凋落物不仅使底物有机组成发生了变化,在一定程度上导致凋落物物理结构紧密程度改变,而且也可能相应地改变了凋落物定殖微生物群落,这些复合影响从不同程度上决定了凋落物分解及其微生物活性对凋落物底物酸解的响应.%To test the effect of substrate acidolysis on litter decomposition of Cunninghamia lanceolata needles and Cinnamomum camphora leaves,we conducted a field experiment in western Hu'nan Province,China.In general,the results showed that mass loss of litter was stimulated by substrate acidolysis,and increased with the magnitude of acidolysis.Moreover,the effect of acidolysis on C.camphora litter was stronger than that on C.lanceolata litter.We found that acidolysis may affect the degradation of C.lanceolata litter through inhibition of microbial activities,including fungal biomass and cellulolytic and ligninolytic enzymes.However,for C.camphora litter,the responses of microbial activities to acidolysis during decomposition depended on the measured variables and decomposition stages.The responses of total mass loss,lignin loss,and cellulose loss of degrading litter to acidolysis differed between the two species,and depended upon decomposition stage (i.e.,early and late stages of litter decomposition).Regarding the litter of C.lanceolata,the mass loss declined with the strengthening of substrate acidolysis (T1 ＞ T2 ＞ T3) at the early stage of decomposition,whereas it improved with increasing acidolysis (T3 ＞ T2/T1) at the late stage of decomposition.For the litter of C.camphora,the opposite was the case at each stage of the decomposition process.Thus,litter substrate acidolysis not only altered organic chemical components and physical compactness,but also altered the microbial community during the processes of litter decomposition.These combined effects,at different levels,determined the responses of litter decomposition and associated microbial activities to substrate acidolysis of litter.