中亚热带不同植被恢复阶段林地土壤磷库特征

以湘中丘陵区檵木—南烛—杜鹃灌草丛(LVR)、檵木—杉木—白栎灌木林(LCQ)、马尾松—柯(又名石栎)—檵木针阔混交林(PLL)、柯—红淡比—青冈常绿阔叶林(LAG)4种林地为对象,采用Tiessen和Moir修正后的Hedley磷(P)分级方法,研究不同植被恢复阶段林地土壤P各分级组分含量及其组成比例。结果表明:随着植被恢复,同一土层全磷(TP)、总无机磷(Pi)、总有机磷(Po)含量增加,NaHCO_3-Pi、NaOH-Pi、HCl-Pi和NaHCO_3-Po、NaOH-Po属于快速积累型,Residual-P属于缓慢积累型,Resin-Pi属于稳定型;不同植被恢复阶段林地土壤Pi以NaOH-Pi为主,Po以NaOH-Po为主,土壤P以Residual-P和Po为主;随着植被恢复,同一土层Po含量占TP的百分比增加,Pi先增加后减少,而Residual-P逐渐下降;不同林地土壤TP及P各分级组分含量均随着土壤深度增加而降低;随着植被恢复,群落植物多样性、群落生物量和凋落物层养分含量及质量的变化显著影响着土壤P各分级组分的含量及其组成比例。

Characteristics of Soil Phosphorus Pool at Different Vegetation Restoration Stages in the Mid-subtropical Region of China

Four different vegetation communities, which represented the primary forest successional sequence in the central hilly area of Hunan Province, China, were chosen in this study. They were:Loropetalum chinense-Vaccinium bracteatum-Rhododendron mariesii scrub-grass-land (LVR), L. chinense-Cunninghamia lanceolata-Quercus fabri shrubbery (LCQ), Pinus massoniana-Lithocarpus glaber-L. chinense coniferous-broad leaved mixed forest (PLL) and L. glaber-Cleyera japonica-Cyclobalanopsis glauca evergreen broad-leaved forest (LAG). The modified phosphorus fractionation method of Tiessen and Moir, which was put forward originally by Hedley, was used to study the differences in the concentrations and composition ratios of phosphorus components at different vegetation restoration stages. The result showed that with the restoration of vegetation, the concentrations of total phosphorus (TP), total inorganic phosphorus (Pi) and total organic phosphorus (Po) increased in the same soil layer. The concentrations of NaHCO₃-Pi, NaOH-Pi, HCl-Pi and NaHCO₃-Po and NaOH-Po belonged to rapid accumulation type, and Residual-P belonged to slow accumulation type, while Resin-Pi stable type. The NaOH-Pi and NaOH-Po were the major components of the Pi and Po in different forest stands, respectively. The phosphorus pool was mainly composed of Residual-P and Po. With the vegetation restoration, the percentages of Po to TP increased gradually in the same soil layer, Pi increased first and then decreased, while Residual-P decreased gradually. The concentrations of TP and each P component decreased in the same forest stand with the increase of soil depth. With the restoration of vegetation, the changes of the diversity of community plant, community biomass, nutrients contents and quality of the litter layer significantly affected the contents of each P component in soil, and subsequently affected the composition ratios of soil phosphorus pool.