土地利用方式对红枫湖入湖流域土壤团聚体磷含量及其形态的影响

以贵州省安顺市红枫湖入湖口4种典型土地利用方式（玉米地、菜园、林地及撂荒地）为研究对象，分别探讨了土地利用方式对0—15em和15～30cm两个层次土壤团聚体总磷含量及其形态的影响。结果表明，不同土地利用方式下，原状土壤及各粒级团聚体总磷含量均表现为玉米地〉菜园〉撂荒地〉林地。土壤各粒级团聚体磷形态含量以ResidualP、NaOH—P、NaHCO3-P为主，其中ResidualP在各土地利用方式中的含量均最高，变幅分别为玉米地28．3％～45．4％、林地61．1％-72．7％、菜园45．9％～53．0％、撂荒地52．1％-72．4％；玉米地和菜园土壤均表现为有机磷含量约为无机态含量的2倍；随团聚体粒径的减小，土壤对总磷含量的贡献率呈减少趋势，土壤团聚体对总磷含量贡献主要集中在5～2mm和2~0．5mm两个粒级中，贡献率均达77％以上，其中耕作土壤（玉米地、菜园）中5-2mm和2-0．5mm两个粒级团聚体中的磷是湖泊面源污染中磷素的主要贡献载体，也是造成湖泊富营养化的关键因素。

Effects of Land Use Types on Phosphorus Forms and Their Contents in Soil Aggregates in Watershed of Hongfeng Lake

Excessive phosphorus （P） in soils may increase the potential to pollute water through runoff and/or leaching. Different land use types may change phosphorus mobility. A study was performed to examine the chemical forms and their contents of P in bulk soil and soil aggregates at 0-15 cm and 15-30 cm under four land use types：cornfields, vegetable fields, forest land and abandoned land in the water- shed of Hongfeng Lake in Anshun, Guizhou Province. Total P contents in bulk soils and soil aggregates were in order of cornfields〉vegetable fields〉abandoned land〉forest land under different land use types. Residual P, NaOH-P, and NaHCO3-P were the major forms in soil aggre- gates at each depth. The residual P was the highest among all P forms in softs under four land use types, and ranged 28.3%-45.4%, 61.1% -72.7%, 45.9%-53.0% and 52.1%~72.4% in cornfield, forest land, vegetable field and abandoned land, respectively. The organic P con- tents were as about 2 times as inorganic P contents in cornfield and vegetable field. Soil P was mainly present in soil aggregates of 5-2 mm and 2-0.5 mm, accounting for more than 77% of soil total P. Phosphorus in aggregates of 5-2 mm and 2-0.5 mm in cultivated soils includ- ing cornfield and vegetable field were the main contributors to lake P and could be the key factor of the lake eutrophication.