中文摘要：

研究了川西亚高山林线交错带土壤细菌、真菌和放线菌三大微生物、细菌生理类群数量及酶活性季节动态．结果表明，土壤微生物主要集中分布在0～15cm表层土壤，其数量及酶活性均随土壤深度的加深而降低．随季节性水热状况的变化，表层0～15cm和15～30cm土层微生物和酶活性各月差异显著（P〈0．05），具明显的季节变化，但各类群变化规律并不完全相同，细菌、真菌、氨化细菌、好氧固氮菌、硝化细菌、有机磷分解菌、好气纤维素分解菌数量及脲酶、蔗糖酶、磷酸酶和多酚氧化酶活性均8月最高，而放线菌、无机磷分解菌、反硝化细菌与嫌气纤维素分解菌数量则6月最高，各微生物及酶活性均4月最低．底层（30-47cm）土壤各微生物和酶活性总体上季节动态不明显．各季节中，氨化细菌、好氧固氮菌、反硝化细菌、有机与无机磷分解菌是8种细菌生理类群中的优势菌群，而纤维素分解菌数量最少，表明林线交错带土壤有机质的分解非常缓慢．

英文摘要：

The seasonal changes about the quantities of microbes and the enzymatic activities were investigated in this paper. The results showed that the quantities of soil microbes and enzymatic activities were mainly concentrated in 0-15 cm soil layer, and rapidly decreased with increasing soil depth. In the topsoil（0-15 cm）, with the change of soil water and temperature in different season, the soil microbes and enzymatic activities were significantly different among different season and had obvious seasonal changes. The quantities of bacteria, fungi, ammonifying bacteria, aerobic nitrogen fixing bacteria, nitrifying bacteria, organic phosphorus-decomposing bacteria and aerobic cellulose-decomposing bacteria, and the enzymatic activities of phosphatases, urease, invertase and polyphenol oxidase rose up the peak in August but in June for actinomyces, inorganic phosphorus-decomposing bacteria, anaerobic cellulose-decomposing bacteria and denitrifying bacteria. However, they were all lowest in April and had no significantly seasonal changes in the subsoil （30-47 cm）. Furthermore, in different season and soil layers, as the dominant physiological groups, the quantities of ammonifying bacteria, aerobic nitrogen fixing bacteria, denitrifying bacteria, organic and inorganic phosphorus-decomposing bacteria were bigger, but cellulose-decomposing bacteria were very smaller, showing that the organic matter decomposed slowly in subalpine timberline ecotone.