川西亚高山不同土地利用类型对土壤微生物量碳动态特征的影响

20 世纪50 到60 年代,川西亚高山林区林分由于大量砍伐后更新,以及近年国家实施重大生态工程项目,土地利用类型发生显著变化。文章选取米亚罗林区典型的原始冷杉暗针叶林、灌木林、草地、云杉林、云杉+红桦混交林、退耕云杉林等6 种不同土地利用类型,以坡耕地为对照,揭示了不同土地利用类型对表层(0~15 cm)和亚表层(15~30 cm)土壤有机碳、微生物量碳含量及土壤微生物熵的动态特征的影响。结果表明:不同土地利用类型的土壤有机碳微生物量碳含量在土壤表层显著大于亚表层(P<0.05);季节动态上土壤有机碳含量冬季最高,其次为夏季,秋季最低,而土壤微生物量碳则表现出相反的动态特征。不同土地利用类型显著影响着土壤有机碳和微生物量碳含量的动态,土壤有机碳、微生物量碳含量坡耕地在4 个季节均为最低,其中,土壤有机碳含量年均值在表层土壤中分别为原始冷杉林、灌木林、草地、云杉+红桦混交林、退耕云杉林、云杉林的23.55%、29.44%、33.12%、43.94%、58.13%和67.63%,亚表层土壤中分别为18.02%、27.30%、32.93%、40.74%、55.26%和58.10%;土壤微生物量碳年均值分别为原始冷杉林、灌木林、草地、云杉林、云杉+红桦混交林、退耕云杉林的20.50%、23.23%、30.63%、36.48%、46.22%和59.07%,在亚表层土壤中则为25.66%、35.65%、40.23%、43.63%、55.34%和66.71%;受不同土地利用类型的影响,土壤微生物熵的动态特征表现出与土壤有机碳含量相反、与土壤微生物量碳含量相一致的规律。

Effect of Different Land Use Patterns on Seasonal Dynamic of Soil Microbial Biomass Carbon in the Subalpine Forest of Western Sichuan,China

During the 1950s and 1960s, the forest had been greatly reduced and degraded, as a long-term over-logging on a large scale, and then, there were many different patterns of plantations and secondary forest. In this paper, in order to assess the effect of land use change on soil organic carbon (SOC) and soil microbial biomass carbon (SMBC), soil samples were taken from primeval Abies spp. forest, Picea spp. forest, Picea spp.+ Betula albo-sinensis mixed forest, shrub forest, converted cropland to Picea spp. forest, grassland, at the same time, slope farmland was set as CK, and their SOC, SMBC contents of different seasons in soil surface (0- 15 cm) and subsurface (15-30 cm) were determined. The results showed that the contents of SOC and SMBC in soil surface were significantly higher than subsurface (P<0.05) under each land use pattern; the content of SOC was the highest in winter, the second highest in summer, the lowest in autumn, but the dynamics of SMBC were opposite to the varies of SOC. The effect of land use on SOC and SMBC contents were very significant, the contents of SOC and SMBC under CK were the lowest in each season. In soil surface, the annual mean content of SOC under CK was only 23.55%, 29.44%, 33.12%, 43.94%, 58.13% and 67.63% of primeval Abies spp. forest, shrub forest, grassland, Picea spp.+ Betula albo-sinensis mixed forest, converted cropland to Picea spp. forest and Picea spp. forest, in soil subsurface the percentages were 18.02%, 27.30%, 32.93%, 40.74%, 55.26% and 58.10%; and the annual mean content of SMBC under CK was only 20.50%, 23.23%, 30.63%, 36.48%, 46.22% and 59.07% of primeval Abies spp. forest, shrub forest, grassland, Picea spp. forest, Picea spp.+ Betula albo-sinensis mixed forest and converted cropland to Picea spp. forest, in soil subsurface the percentages were 25.66%, 35.65%, 40.23%, 43.63%, 55.34% and 66.71%. With the effect of land use, the seasonal dynamics of qSMB were the same as the SMBC content and the opposite to the SOC content, but the order were not obvious.