佛山地区存留自然林和存留人工林的土壤无机磷组分

为探讨热带亚热带森林，尤其城市及其周边地区残存森林土壤磷的有效性，对佛山地区14个残存林(7个自然林和7个人工林)的0~3 cm和3~23 cm矿质土壤的P有效性进行研究。结果表明，铁结合态无机P和还原剂可溶解无机P是土壤无机P的主要组分。在0~3 cm矿质层中，自然林土壤铝结合态无机P、Bray 1提取无机P和总无机P含量显著高于人工林；而在3~23 cm矿质土层中，自然林土壤钙结合态无机P含量显著高于人工林。其它土壤营养指标在自然林和人工林间差异不显著。相关分析结果表明，土壤有机质含量与钙结合态无机P除外的其它无机P组分含量均成显著正相关。聚类分析结果表明14个残存林土壤P有效性可分成3组，整体上人工林土壤P有效性比自然林低。这有助于认识城市化影响下城市及其周边地区残存森林土壤营养状况及加强养分管理。

Soil Inorganic Phosphorus Fractions of Remnant Native and Plantation Forests in Foshan Region

Soil phosphorous (P) availability is always thought to be a limiting factor for ecosystem primary productivity in the highly weathered tropical and subtropical areas, but our knowledge about soil P availability in tropical and subtropical forests is still poor, particularly in remnant native forests and frequently disturbed plantation forests in the urban and suburban areas. The soils at 0-3 cm and 3-23 cm mineral depths from 14 forest patches in Foshan region (seven native forest patches and seven plantation forest patches) were collected, and pH in water and concentrations of organic carbon (C), total nitrogen (N), total P, Bray-1 Pi and sequential extractable inorganic P fractions to estimate soil P availability were determined. The results showed that Fe-Pi and reductant soluble inorganic P were major inorganic P fractions at the study forest patches. Most of the selected soil nutrient measures did not differ significantly between forest types in both soil layers. The concentrations of Al-Pi, Bray 1-Pi and total Pi in the 0-3 cm mineral soil layer and Ca-Pi in the 3-23 cm mineral soil layer were significantly lower at the plantation forest patches than those at native forest patches. Concentrations of organic C, total N, total P and all P fractions were significantly higher in 0-3 cm mineral soil layer than those in the 3-23 cm mineral soil layer for both forest types. Correlation analysis indicated that soil organic matter concentration was significantly and positively correlated with soil concentrations of all inorganic P fractions except Ca-Pi. Fourteen selected forest patches could be divided into three groups according soil P availability by Cluster analysis. Generally, the plantation forest patches were lower in soil P availability compared to native forest patches. These could help us for understanding the soil nutrient status and strengthen nutrient management at remnant forest patches in the urban and suburban areas.