【摘要】 植物残体可以修正土壤酸度,但其作用机理还有很大争议,本研究评估森林凋落物作为酸碱缓冲体系的能力,它可能是调节土壤酸度的重要机理之一。凋落物材料取自华南重要的人工林类型及一个地带性顶极森林群落,将材料用不同pH酸溶液提取,并用酸碱进行滴定。结果表明,凋落物本身是一个极强的酸碱缓冲体系,它使浸提液酸度保持不变,并对添加的酸碱起显著的缓冲作用。首次发现两个豆科树种凋落物马占相思(Acacia mangiumWilld)与大叶相思(Acacia auriculaiformis A.Cunn)具有很高的pH值(约pH 6.0),约高于土壤酸度2个pH单位,每年凋落于地表的枯落物层通过缓冲机理可以提高雨水0.1至0.4 pH单位。其它人工林凋落物酸度约为pH4.0,与它们生长的土壤酸度相似。溶液中无机离子组成上的差异不能完全解释凋落物pH格局,但高钠低硝态氮可能是两个豆科树种高pH的一个重要原因。地带性顶极群落12个树种加权酸度为pH 3.90,明显低于土壤酸度(pH4.19),因而,凋落物是林下土壤进一步变酸的驱动因素;发现一个种凋落物(山竹子(Garcinia oblongifolia))酸度极低(pH 3.19)并且缓冲力极强,该种植物生长的土壤将难于通过施用石灰等措施对酸度进行调节,它影响下的土壤环境将影响其它植物的入侵。观光木(Tsoongiodendron odorum Chun)凋落物更多还原

【Abstract】 The role of forest litter as an acid-base buffering system was assessed by litter fromplantation and natural forests in South China. Samples were either extracted with acid solutions or ti-trated with acid or base solutions. Litter was found to be a strong acid-base buffering system. Two legumespecies, Acacia mangium Willd and A. auriculaiformis A. Cunn, had very high litter pH values of around 6,which was 2 pH units higher than that of the soil where they grew. Litter of all other plantation species hadlitter pH of around 4, similar to that of the soil. Both legume species have high potential to neutralize soilacidity and the litter layer could act to shield soil against acid rain. The current stand of two legumespecies was estimated to be able to raise rain acidity by 0.1 to 0.4 pH units. Inorganic ions did not fullyexplain the pH pattern of different litter extracts, but high sodium and low nitrate partly accounted for thehigh pH of the two legume species. Some natural forest species had extremely low pH. As a whole, thelitter of the natural climax forest was the driving force of soil acidification. Although plant residues arestrong acid-base buffering system and able to adjust acidity of environment, only a few species can beexpected to make soil more acid or alkaline through this mechanism since most species have litter pHvalues similar to those of soil where they grow.更多还原