川西亚高山林线过渡带土壤特性研究

Soil Properties of the Subalpine Timberline Ecotone in Western Sichuan

初步研究了川西亚高山林线过渡带残积母质土壤（0-15 cm,15-30 cm和15-47 cm）物理、化学及生物学特性。结果表明,随土层深度加深,林线过渡带土壤石砾和物理性砂粒含量分别达35%～86%和67%～82%,粘粒和物理性粘粒为2%～9%和16%～24%,土壤团聚度和结构水稳性分别为9%～25%和20%～29%,容重为0.82～1.58,表明整个土壤砂粒、粉粒和粘粒比例失调,其物理结构较差。表层（0-15 cm）土壤有机质、阳离子交换量（CEC）、全N和P、有效N和P含量,细菌、真菌、放线菌、细菌生理类群数量以及微生物量碳和氮含量,脲酶、蔗糖酶、酸性磷酸酶、中性磷酸酶、碱性磷酸酶、多酚氧化酶和过氧化氢酶等酶活性均显著高于下层土壤。整个土壤微生物以细菌为主要类群,占85%～95%,其次是真菌和放线菌,细菌生理类群数量排序为氨化细菌〉好氧固氮菌〉有机磷分解菌〉无机磷分解菌〉反硝化菌〉硝化细菌〉好气纤维素分解菌〉嫌气纤维素分解菌,且表层显著高于下层。林线过渡带土壤较低的有效养分含量可能是影响其植物生长的关键因子之一。

The physical, chemical and biological properties of the soil （in 0-15 cm, 15-30 cm and 30-47cm soil layers） mainly taken place in residual deposits of the subalpine timberline ecotone in western Sichuan were investigated in 2006. The results showed that in 0-47 cm soil layer, the contents of seree, physical silt, clay and physical clay, aggregate degree, structure coefficient and bulk density varied from 35% to 86%, 67% to 82%, 2% to 9%, 16% to 24%, 9% to 25%, 20% to 29% and 0. 82 to 1.58 respectively, showing that the soil physical structure was unfavorable because of the maladjusted percentage of the soil sand, silt and clay. Furthermore, the contents of cation exchangeable capacity, organic matter, total N, total P, available N, available P, microbial biomass carbon and nitrogen, the quantities of bacteria, fungi, actinomyces the physiological groups of bacteria, and the enzymatic activities of acid phosphatases, neutral-phosphatase, phosphorylatio, urease, invertase, eatalase and polyphenol oxidase in the topsoil （0--15 cm） were higher than those in the undersoil. In 0--47 cm soil layer, the quantities of bacteria were highest among microbial population concentrating mainly in 0-- 15 cm soil layer. The quantities of bacterial physiological groups show an order of ammonifying,bacteria;〉aerobie nitrogen fixing bacteria〉organie phosphorus-decomposing bacteria〉inorganic phosphorus-decomposing bacteria〉denitrifying bacteria〉nitrobacteria〉aerobic- cellulose-decomposing baeteria〉anaerobic cellulose-decomposing bacteria. The lower available nutrient may be one of the keys to affect the growth of the plants in subalpine timberline ecotone.