中文摘要：

以撂荒地为对照,油松人工幼龄林（1315 a）、中龄林（2527 a）和成熟林（4143a）为研究对象,分析了黄土高原典型油松人工林不同生长阶段土壤微生物生物量碳的变化特征及其影响因素.结果表明：油松幼龄林、中龄林和成熟林土壤微生物生物量碳分别为93.08、122.64和191.34 mg·kg-1,随发育阶段呈显著增加趋势,且显著高于撂荒地（42.93mg·kg-1）.土壤微生物生物量碳随土层深度呈逐渐降低的趋势,在020 cm土层油松幼龄林、中龄林和成熟林较撂荒地分别提高了134.2%、221.7%和375.7%,在2040 cm土层分别提高了101.3%、164.3%和337.5%,在4060 cm土层分别提高了103.1%、146.2%和303.0%.油松胸径、高度、根系生物量以及枯落物的厚度、生物量、全氮含量与土壤微生物生物量碳呈显著正相关;土壤有机碳、全氮含量及土壤含水量与土壤微生物生物量碳呈显著正相关.主成分分析表明,油松根系生物量、枯落物生物量和土壤有机碳含量是影响黄土高原油松人工林微生物特征的主要因子.油松生长过程中,枯落物和根系凋落物显著影响了土壤有机碳含量,提高了土壤微生物生物量碳.

英文摘要：

By taking an abandoned land as control and the young（ 13- 15 year-old）,middle-age（ 25-27 year-old） and mature（ 41-43 year-old） plantations of Pinus tabuliformis as research objects,the variation characteristics and impact factors of soil microbial biomass carbon（ MBC） for the P. tabuliformis plantations in 0-60 cm soil layer were studied. Results showed that the average MBC at the young,middle-age and mature plantations was 93.08,122.64 and 191.34 mg·kg-1,respectively,which showed a significant increase with growth stage and was significantly higher than the abandoned land（ 42.93 mg · kg-1）. The average MBC contents gradually decreased with soil depth. Compared with the abandoned land,the average MBC at the young,middle-aged and mature plantations respectively increased by 134. 2%,221. 7% and 375.7% in the 0- 20 cm soil layer,101.3%,164.3% and 337.5% in the 20-40 cm soil layer,and 103.1%,146.2% and 303.0% in40-60 cm soil layer. The MBC for the whole soil layer of 60 cm had a highly significant correlation with the DBH,height and root biomass of the P. tabuliformis plantation,as well as the thickness,biomass and total nitrogen of litter. Meanwhile,the MBC also showed significant correlations with soil organic carbon（ SOC）,total nitrogen and moisture content. Principal component analysis showed that the root biomass,litter biomass and SOC were the principal factors affecting MBC. The P. tabuliformis plantation significantly increased SOC content mainly through litter of leaf and root and improved the MBC in the growth process.