岩溶生态系统土壤非保护性有机碳含量研究

Content and Distribution of Unprotected Soil Organic Carbon in Karst Ecosystem

通过现场采样及室内测定方法,对岩溶天然林、灌丛和人工林土壤的非保护性有机碳进行了研究。结果发现,在0～10cm表层土壤,灌草丛土壤颗粒有机碳含量是天然林土壤的1.40倍,土壤轻组有机碳含量是天然林土壤的4.02倍;但随土层深度增加,天然林土壤颗粒有机碳分配比例和轻组有机碳分配比例大于灌丛土壤,且灌丛土壤有机质逐渐向大团聚体富集,而天然林不同深度土壤大团聚体都富集有机质。天然林土壤和人工林土壤<0.05mm的颗粒有机碳富集系数差异很小,但>0.1mm颗粒和0.1～0.05mm颗粒的有机碳富集系数差异相对较大,尤其在土壤表层有明显的差异。颗粒有机碳、轻组有机碳、不同深度土层土壤有机碳与水稳性团聚体之间存在显著的相关性。

Soil organic carbon, particulate organic carbon （POC）, light fraction organic carbon （LFOC）, organic carbon contents in the different particles fractions, contents of water-stable aggregates and soil organic matter contents in aggregates obtained with dry sieving method under different karst ecosystem such as natural forest, shrub and monocuhure plantations were studied to elucidate their characteristics and correlations between each other quantitatively in this paper. The results showed that in 0-10 cm soil surface layers, the content of POC in shrub-grass soils was as much 1.40 times as that in natural forest, and the content of LFOC was as much 4.02 times as that in natural forest. With the depth increase of soil layers, the proportion of POC and LFOC in soil profile in natural forest was higher than that in shrub-grass, and only bigger soil aggregates from the shrubbery tendered to contained soll organic matter. The enrichment factors of soil organic carbon of particle fractions under 2 land use types, which size were below 〈0.05 mm, differentiated a little, but particle fractions （〉0.1 mm and 0.1 - 0.05 mm） had a significant difference between natural forest and monocuhure plantations, particularly in the soil surface layers. There were positive correlations among these indexes, particularly a significant positive correlation between LFOC and POC.