川西亚高山林线交错带及邻近植被土壤细菌生理群数量特征

Quantitative Property of Different Soil Bacterial Physiological Groups in Subalpine Timberline Ecotone and Adjacent Vegetations in Western Sichuan

研究川西亚高山林线交错带及上缘流石滩草甸和下缘冷杉林土壤8种细菌生理群数量的空间分布和时间动态特征。结果表明:不同植被细菌生理群数量均随土壤深度加深而降低;0～30cm土层硝化细菌、反硝化细菌、好气固氮菌、有机磷分解菌和好气纤维素分解菌数量表现为林线交错带>下缘冷杉林>上缘流石滩草甸,而氨化细菌、无机磷分解菌和厌气纤维素分解菌除上缘流石滩草甸最低外,林线交错带与下缘冷杉林无显著差异;氨化细菌、有机和无机磷分解菌是各植被土壤中的优势菌群,纤维素分解菌数量最低;在0～15cm土层,上缘流石滩草甸各菌群数量4月最低,6月最高,林线交错带及下缘冷杉林各菌群数量亦4月最低,厌气性的反硝化细菌与厌气纤维素分解菌6月最高,其余菌群均8月达最大值;而各植被底层土壤各细菌生理类群数量无明显时间动态规律;林线交错带及邻近植被细菌生理群的空间分布与时间动态与土壤的立地条件、营养成分、水热条件变化关系密切。

The ecological distribution and temporal dynamics of soil bacterial physiological groups in subalpine timberline ecotone and its upper boundary of scree meadow and below boundary of fir forest in Western Sichuan were investigated and analyzed with the plate count and MPN methods. Results showed that populations of soil bacterial physiological groups decreased with increasing soil depth. In 0-30 cm soil layer,the quantities of nitrobacteria,denitrifying bacteria,aerobic nitrogen fixing bacteria,organic phosphorus-decomposing bacteria and aerobic cellulose-decomposing bacteria were in a sequence of timberline ecotone soilfir forest soilscree meadow soil. There was no significant difference for ammonifying bacteria,inorganic phosphorus-decomposing bacteria and anaerobic cellulose-decomposing bacteria between timberline ecotone and fir forest soil,while those bacteria in the two soils were more than that in scree meadow. The ammonifying bacteria,inorganic and organic phosphorus-decomposing bacteria were dominant physiological groups in each soil,while the cellulose-decomposing bacteria were the scarcest group. Furthermore,the populations of soil bacterial physiological groups were the least in 0-15 cm soil layer of scree meadow in April and the most in June,whereas the groups were also the least in the topsoil （0-30 cm） of timberline ecotone and fir forest,but all the most in August except denitrifying bacteria and anaerobic cellulose-decomposing bacteria which were the most in June. There was no significant temporal dynamics in the subsoil under three kinds of vegetations. In general,the spatial distribution patterns and temporal dynamics of various soil bacterial physiological groups in timberline ecotone and adjacent vegetations were to certain degree different,depending on the site condition,soil nutrition and water-heat conditions.