喀斯特石冠腐殖土及其对NH4+-N的吸附性能——以云南石林为例

石冠腐殖土在喀斯特地区广泛分布，具有维系喀斯特生态系统植物多样性、截留沉降养分和水分等重要的生态功能。本文以云南石林为例，选择典型石漠化生态系统、人工林生态系统和次生林生态系统，实地取集各类小生境的石冠腐殖土样，并进行NH4+-N吸附实验，探究石冠腐殖土对NH4+-N的吸附动力学和等温吸附特征。结果表明:石漠化生态系统、人工林生态系统和次生林生态系统每平方米岩石投影面积的石冠腐殖土分别为40.45±25.38 g、38.89±9.92 g和397.66±142.71 g；石冠腐殖土对NH4+-N的吸附动力学遵循准二级反应动力学方程，2 min内能完成吸附量的65%～75%，吸附平衡时间约为20 min；腐殖土对氨氮的吸附量随加入NH4+-N浓度的升高而增加，吸附等温线符合Boxlucas1模型，依据此模型计算出的石漠化生态系统石冠腐殖土的吸附性能最大，最大吸附量约7.79 g/kg，人工林次之，为5.29 g/kg，次生林的吸附性能最小，吸附量仅为4.73 g/kg，腐殖土对氨氮的截留率为20%～50%。 

Humus on karst rock outcrops and their adsorption of ammonia nitrogen:A case from three ecosystems of Shilin,Yunnan

A lot of researches had paid attention on canopy humus. Nevertheless, little information is available about the rock outcrop canopy humus in karst ecosystem. Humus offers the growth matrix and nutrients for lithobiontic communities. Humus were collected on the carbonate rocks located in three karst ecosystems with different degree of rocky desertification and quantified; and their adsorption capability on ammonia were investigated in this study by means of simulation experiments. The results showed that the humic substanceson per square meter are 40.45±25.38 g, 38.89±9.92 g and 397.66±142.71 g in stony desertification, manmade forest and secondary forest ecosystems, respectively. They were significantly different in three ecosystems. When different ammonia solutions were added, humus would absorb 65%~75% within 2 min and adsorption equilibrium time was approximately 20 min. The dynamic adsorption data of NH4+-N were well described by pseudo second order reaction rate model. Adsorption isotherm of NH4+-N on three kinds of humus could be well fitted by Boxlucas 1. The equilibrium adsorption capacity of humus followed an increasing order from secondary forest ecosystems (4.73 g/kg), to manmade forest ecosystems (5.29 g/kg), and then stony desertification ecosystems (7.79 g/kg). The retention rates of humus for added NH4+-N was 20%~50%. It revealed that carbonate rock in southern China function as a nutrient pool, even in oligotrophic stony desertification ecosystem.