缙云山4种林分土壤无机磷与活性铝的含量及分布

为探索不同林分对土壤中无机磷与活性铝的含量及分布的影响，以及无机磷与活性铝之间的相互关系，以在我国西南地区酸性土壤上的农林经营管理提供理论和实践依据。研究以缙云山广泛分布的4种林分类型：山莓、马尾松、楠竹和柑橘林土壤为对象，采用酸性土壤无机磷分级方法和铝试剂比色法测定了土壤剖面A、B和C层中各形态的无机磷与活性铝的含量，分析了不同林分土壤中无机磷和活性铝的含量和分布特征。结果表明，林分类型显著影响土壤中无机磷与活性铝的含量与分布，且铁磷(Fe-P)、交换态铝(Ex-Al)和羟基铝(Hy-Al)的含量和比例还受到土壤层次的影响。4种林分相比，山莓林能促进闭蓄态磷(O-P)的形成，而马尾松、楠竹和柑橘林则有利于Al-P、Fe-P和Ca-P的形成；柑橘林有利于低活性的腐殖酸铝(Al-AH)形成，而山莓、马尾松和楠竹林促进高活性的Ex-Al或Hy-Al溶出；Ex-Al、Al-P和Fe-P在土层的分布上有表层富集现象，而Hy-Al集中分布于B层。此外，土壤Ex-Al和Al-P与Fe-P之间，Hy-Al和Ca-P之间均呈显著(P<0.05)正相关。因此，林分类型显著影响土壤无机磷与活性铝的含...

Content and distribution of inorganic phosphorus and labile aluminum in soil of four forest types in Jinyun Mountain

Phosphorus (P) is an essential element for plant growth, development and metabolism. Soil is a direct donor of phosphorus for plants. Generally, total phosphorus (TP) is plenty in most soils, but its availability to plants is very low. Aluminum (Al) is the most abundant metal element in the earth''s crust. When the soil is getting acidified, Al in the forest soil can be activated into Al³⁺ (exchangeable Al, Ex-Al) or Al (OH)²⁺, Al (OH)₂⁺ (hydroxyl-Al, Hy-Al), which might precipitate HPO₄^2-, H₂PO₄^-, and PO₄^3- into hard-to-dissolve P and reduce the P availability in consequence. How to prevent the decrease of P availability caused by the dissolution of Al from acidic soil, which is one of the urgent problems to be solved in forest land management. Forest type and soil layer might affect the characteristics and relationships between inorganic phosphorus (IP) and labile Al, which remains poorly understood up to now. The present study aimed to determine the influence of forest type and soil layer on the concentration and distribution of IP and labile Al in soil, in addition to the correlation between labile Al and IP. The soil was collected by digging in three soil layers (A, B and C layer) of four forest types of Rubus corchorifolius, Pinus massoniana, Phyllostachys pubescens and Citrus reticulata forest in Jinyun Mountain, Chongqing, China. Concentrations of IP and labile Al fractions were measured using the traditional method. Results showed that concentrations and proportions of IP and labile Al in soil were significantly affected by forest types and that of iron-bound P (Fe-P), Ex-Al and Hy-Al in soil were significantly different in soil layers. Among the four forest types, Rubus corchorifolius promoted the formation of occluded P (O-P). Whereas, Pinus massoniana, Phyllostachys pubescens and Citrus reticulata were in favor of the formation of aluminum-bound P (Al-P), Fe-P and calcium-bound P (Ca-P). Citrus reticulata was favorable for the formation of low-active Al species (humic acid-Al, Al-AH), while Rubus corchorifolius, Pinus massoniana and Phyllostachys pubescens contributed the dissolution of labile Al from low-active into high-active species (Ex-Al or Hy-Al). In soil layers, Ex-Al, Al-P and Fe-P mainly enriched in the surface among the three soil layers. Hy-Al concentrated in the second soil layer. Meanwhile, the correlations were significantly positive between Ex-Al and Al-P and Fe-P or between Hy-Al and Ca-P in the soil of four forest types. The concentration and distribution of IP and labile Al fractions in soil were significantly affected by forest types. The dissolution of labile Al from low-active into high-active species significantly affected the concentrations of Al-P, Fe-P and Ca-P. This study can provide theoretical and practical basis for the management of agriculture and forestry on acid soils in southwest China.