祁连山西水林区土壤阳离子交换量及盐基离子的剖面分布

以祁连山西水林区分布的棕钙土、灰褐土、栗钙土和高山草甸土为对象,研究了阳离子交换量和盐基离子(K+、Na+、Ca2+、Mg2+)的剖面分布规律及其与土壤理化因子的关系。结果表明:土壤阳离子交换量(CEC,介于4.80—48.10 cmol/kg)和盐基总量(TEB,介于4.67—21.34 cmol/kg)随剖面深度的增加逐渐减小,不同土壤类型的大小顺序为:灰褐土>高山草甸土>栗钙土>棕钙土;土壤盐基组成以Ca2+、Mg2+为主(占TEB的比例平均为71.6%、22.9%),K+、Na+所占比例较低(占TEB的比例平均为3.3%、2.2%);棕钙土、灰褐土和栗钙土盐基离子的剖面分布由浅至深呈现:K+≈Ca2+>Na+≈Mg2+,高山草甸土盐基离子则呈现:K+>Na+>Mg2+>Ca2+。不同土壤类型间盐基离子的含量及饱和度随发生层次不同存在较大差异。土壤有机质是CEC的主要贡献因素,粉粒对CEC也有显著的促进作用,而砂粒、CaCO3对CEC有显著抑制作用。土壤生物复盐基作用弱于淋溶作用,造成盐基饱和度较大(BSP,介于44.4%—97.2%),并随剖面深度的增加逐渐增大。相关性分析表明,土壤交换性Na+、Mg2+的含量及饱和度均呈极显著正相关,交换性Na+、Mg2+饱和度与CaCO3含量呈极显著正相关;pH值与BSP呈极显著正相关;土壤速效P含量与CEC呈极显著正相关,速效K含量与交换性K+含量呈极显著正相关。

Soil cation exchange capacity and exchangeable base cation content in the profiles of four typical soils in the Xi-Shui Forest Zone of the Qilian Mountains

Abstract: Soil cation exchange capacity (CEC) has been used as an indictor of soil fertility and buffering capacity. The exchangeable base cation content and saturation percentage reflects the bioavailability and movement of soil nutrients. This study was conducted to determine the distribution of CEC and exchangeable base cations in the profiles of four typical soils in the Xi-Shui Forest Zone of the Qilian Mountains. The soil types were brown calcic (BC) soil, grey cinnamon (GC) soil, chestnut soil (CH) soil, and alpine meadow (AM) soil. Three separate profiles (replications) were selected for each soil type. The profiles were divided into A, B, and C horizons and then sampled, making a total of 36 soil samples. Soil CEC as well as exchangable K , Na , Ca2 , Mg2 were determined in the laboratory. Differences in the cation exchange capacity among soil types and horizons were analyzed by analysis of variance and multiple comparisons. Correlation analysis was also conducted to determine the relationships between soil cation exchange properties and soil physico-chemical properties such as soil organic carbon, total N, pH, CaCO3, available P, available K, clay (<0.002 mm) content, silt (0.002-0.02 mm) content and sand (0.02-2 mm) content. The results indicated that CEC in the profiles ranged from 4.80 to 48.10 cmol?kg-1 and the total exchangeable base (TEB) content ranged from 4.67 to 21.34 cmol?kg-1. Both the CEC and the TEB content decreased as soil depth increased. The GC soil had the highest CEC and TEB content followed by the AM soil, the CH soil, and then the BC soil. Averaged across the four soil types, exchangeable Ca2 comprised 71.6% of the TEB content, exchangeable Mg2 comprised 22.9% of the TEB content, exchangeable K comprised 3.3% of the TEB content, and exchangeable Na comprised 2.2% of the TEB content. For the BC, GC, and CH soils, the exchangeable Mg2 and Na content tended to be greater in the upper part of the soil profile whereas the exchangeable Ca2 and K content tended to be greater in the lower part of the soil profile. For the AM soil, the exchangeable Ca2 content tended to be greater in the upper part of the soil profile, the exchangeable Mg2 and Na content tended to be greater in the middle part of the soil profile, and the exchangeable K content tended to be greater in the lower part of the profile. The relative order of the exchangeable cations and the saturation percentage in different soil types varied among the horizons. Soil organic matter was the major factor contributing to CEC. Soil CEC increased as the silt content increased, but decreased as the sand and CaCO3 contents increased. The base saturation percentage (BSP) ranged from 44.4 to 97.2% among the four soil types. The BSP increased as soil depth increased because the recovery of base saturation due to biological factors is weaker than the effect of eluviation. Correlation analysis indicated that soil exchangeable Na content and saturation percentage were positively correlated with exchangeable Mg2 (P<0.01). The saturation percentage of exchangeable Na and Mg2 were positively correlated with the soil CaCO3 content (P<0.01). Furthermore, there were highly significant positive correlations between pH and BSP, available P and CEC, and available K and exchangeable K (P<0.01).