黄土高原典型土壤有机碳和微生物碳分布特征的研究

以阐明黄土高原典型区域土壤有机碳(SOC)含量和储量及微生物碳(Mc)含量随土壤类型、土层和土地利用方式变异规律为目的,研究了从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨凌)等典型土壤的SOC含量和储量及Mc含量的变化特征。结果表明,不同土壤类型、不同土层SOC和Mc含量存在显著差异。同一土壤类型SOC和Mc含量在0～60cm随土层深度增加下降很明显,60～120cm土层有轻微下降,120cm土层以下低而稳定,同层次土壤从南到北,SOC、Mc和SOC储量含量显著下降,均以土垫旱耕人为土最高,黄土正常新成土次之,干润砂质新成土最低,且差异显著(P<0.05);0～200cm土层SOC总储量也沿土垫旱耕人为土(102.23±30.12t/hm²)、黄土正常新成土(67.78±9.23t/hm²)、干润砂质新成土(27.07±4.59t/hm²)依次下降;土垫旱耕人为土、黄土正常新成土和干润砂质新成土在100～200cm土层SOC累积量分别是0～100cm土层的65%、74%和58%,因此在研究黄土高原SOC贮量时必需考虑深层贮量的贡献。Mc随土壤类型的变化趋势与SOC基本相同,与SOC间存在极显著正相关关系(P<0.01);土壤Mc/SOC比值范围为0.005～0.05,土地利用仅对干润砂质新成土和土垫旱耕人为土SOC含量和储量影响显著(P>0.05),但对3种土壤Mc和Mc/SOC比值均产生显著影响;与农田土壤相比,草地土壤Mc和Mc/SOC比值均明显增加,这一结果说明用Mc和Mc/SOC比值更能有效反映土壤质量的变化。

Distribution Characteristics of Soil Organic Carbon and Microbial Biomass Carbon on the Loess Plateau

The soil organic carbon(SOC),soil microbial biomass carbon(Mc) and their relationship of the following soils on the Loess Plateau i.e.,Ust-Sandiic Entisols(Shenmu),Los-Orthic-Entisol(Yan'an) and Eum-Orthic Anthrosol(Yangling) were investigated to assess the impacts of location and soil depth(0-200cm) on the contents and to cumulate the first dates to comprehend the soil C on the Loess Plateau.The result showed that the contents of SOC and Mc were different under different soil types and soil depth.In the same location,the contents of SOC and Mc in the profiles decreased remarkably within 0-60cm,decreased slightly within 60-120cm and remained low and stable under 120cm.From south to north on the Loess Plateau,the contents of SOC,Mc and soil organic carbon storage decreased significantly.Within 0-200cm soil depth,the soil organic carbon storage is 102.23±30.12t/hm²,67.78±9.23t/hm² and 27.07±4.15t/hm² in Eum-Orthic Anthrosol,Los-Orthic-Entisol and Ust-Sandiic Entisols respectively.The soil organic carbon storage in 100-200cm of the above three types of soil were 65%,74% and 58% of carbon storage in 0-100cm respectively.Soil organic carbon storage in soil depth was important to assess the storage of organic carbon on the Loess Plateau.Mc was significantly related with SOC(P<0.01).The range of Mc/SOC ratio was 0.005-0.05.Though the use of land was closely related with the contents of SOC and soil C/N in Ust-Sandiic Entisols and Eum-Orthic Anthrosol,there was close relationship with the contents of Mc and Mc/SOC(P>0.05) in the three types of soil.The contents of Mc and Mc/SOC in grassland soil increased slightly compared with that of farmland.