喀斯特高原典型小流域土壤有机碳及其组分的分布特征

以贵州省清镇王家寨为喀斯特高原典型样区,采用网格布点法,调查研究了土壤总有机碳（SOC）、可溶性有机碳（DOC）和微生物生物量碳（MBC）的分布特征。研究结果表明：灌木林地表层土壤SOC、DOC和MBC含量分别为56.86、68.74mg·kg^-1和264.12mg·kg^-1,均显著高于旱地与水田（P〈0.05）;各土地利用方式表层土壤微生物熵（MBC/SOC）值处于0.45%～0.55%之间,土地利用方式对土壤SOC及其组分均有显著影响。协方差分析表明,土壤MBC受土地利用方式和pH的影响较大,土壤SOC和DOC受海拔高度的影响较大。不同土地利用方式下土壤SOC与MBC无相关性,而DOC与MBC的相关性正负各异。3种土地利用方式剖面土壤中,灌木林地0～30cm各土层MBC含量差异显著（P〈0.05）,水田20～30cm土层DOC含量显著低于0～20cm各土层。表层（0～10cm）土壤SOC密度以灌木林地最大,但旱地（155.97t·hm^-2）和水田（107.92t·hm^-2）1m以内土体的有机碳密度显著高于（P〈0.05）灌木林地（76.14t·hm^-2）,结合土层厚度,水田与旱地有机碳储量高于灌木林地。研究表明加强保护灌木林地,对农耕地实行秸秆还田,将有利于区域土壤有机碳的积累和区域生态的恢复,维持区域的可持续发展。

Characteristics of the Distributions of Soil Organic Carbon and Main Components in a Typical Catchment in the Karst Plateau

Understanding the distributions of soil organic carbon（SOC ） and its main fractions in a typical Karst catchment is a fundamental issue for restoring and reconstructing the degraded Karst ecosystems in Southwest China. 248 regular grid designed soil samples were collect- ed at the Wangjiazhai Village of Qingzhen County in Guizhou Province （a typical Karst plateau） in Jan. 2010, and their SOC, dissolved organ- ic carbon（DOC）, and microbial biomass carbou（MBC） were determined. The results showed that the contents of SOC, DOC and MBC in the topsoils（0-20 cm） of shrub land were 56.86 g· kg^-1, 68.74 mg· kg^-1 and 264.12 mg·kg^-1, respectively and they were significantly higher than those in the topsoils of upland and paddy field（P〈0.05 ）. The ratios of SOC/MBC ranged from 0.45% to 0.55% in the topsoils under different land use types. SOC and its main fractions were significantly influenced by the land use types. Covariance analysis showed that MBC was ap- parently influenced by land use type and pH, while SOC and DOC were influenced by geographic latitude. No significant correlation was found between SOC and MBC, but the correlations between DOC and MBC were variable under different land use types. The MBC contents were significantly decreased with the increase of soil depths within 0-30 cm for shrub land（P〈0.05 ）. The contents of DOC for paddy field in the 20-30 cm soil were significantly lower than those in the 0-20 cm soil（P〈0.05 ）. The SOC density in the very topsoils （0-10 cm） in shrub land was higher than those in other land use types, but in the 1 m soil profile, the SOC densities in upland（ 155.97 t·hm^-2） and paddy（ 107.92 t·hm^-2） were significantly higher than that in shrub land （76.14 t·hm^-2） （P〈0.05）. Therefore, the upland and paddy field seem favor for the SOC accumulation in soils, compared with the shrub land. However, in a comprehensive manner, the protection of shrub land and the deploy-ment of straw return practice in the agricultural fields are eventually helpful for the SOC accumulation, the restoration of the regional ecologi-cal environment and the regional sustainable development.