元阳梯田土壤碳氮的垂直分布特性

 对元阳梯田3个海拔梯度［高海拔（1615~1682m）、中海拔（1532~1555m）和低海拔（1445~1468m）］表层土壤（0~30cm）碳氮组分的含量现状与分布特征进行了研究。结果表明：元阳梯田表层土壤有机碳（TOC）总体达到二级水平，而土壤全氮（TN）、pH值和微生物量碳氮(MBC，MBN)含量较低，土壤溶解性有机碳氮（DOC，DON）含量及其占土壤有机碳、全氮的比值较高，土壤易氧化碳（ROC）和轻组碳氮（LFC，LFN）含量处于中等水平。上述指标均呈现出随海拔的下降而降低的趋势，且元阳梯田土壤DOC，DON，ROC，LFC和LFN与梯田海拔之间呈显著正相关关系（P<005）。元阳梯田土壤TOC，TN，MBC，MBN及NH+4 N含量在3个海拔梯度之间均没有显著差异性；而土壤pH值、DON，ROC，LFC和LFN含量均在高海拔梯度显著高于低海拔梯度（P<005）

Vertical Variation Characteristics of Soil Carbon and Nitrogen in Yuanyang Terraced Paddy Soils

The carbon and nitrogen contents and distribution characteristics of surface layer soil（0~30 cm） at three altitudes ［High altitude（1615~1682 m）, Medium altitude（1532~1555 m）and Low altitude（1445~1468m）］ in Yuanyang terraced paddy soils were studied. The results showed that: the surface layer soil organic carbon（TOC） content was up to the “second” level in average, but the soil total nitrogen (TN) content, pH value and microbial biomass carbon and nitrogen (MBC, MBN) contents were low, the soil dissolved organic carbon and nitrogen (DOC, DON) contents, DOC/TOC ratio and DON/TN ratio were high, and the soil readily oxidizable organic carbon (ROC) content, light fraction carbon and nitrogen (LFC, LFN) contents were medium level. In general, all of the indexes mentioned above decreased along with the fall of altitude, and the altitude showed significant positive relation (P<005) to the soil DOC, DON, ROC, LFC and LFN. There were no significant difference in soil TOC，TN, MBC, MBN and NH+4 N contents among the three altitudes, and the soil pH value, DON, ROC, LFC and LFN contents at high altitude were significantly higher than that at low altitude（P<005）.