亚热带丛枝和外生菌根森林土壤酸缓冲性能及其主要影响因素

Soil acid buffering capacity of subtropical arbuscular and ectomycorrhizal forests and its main influencing factors

土壤酸缓冲能力在土壤抵御施肥和氮沉降等干扰引起的土壤酸化方面起重要作用,是维持土壤功能稳定的重要因素。与丛枝菌根真菌和外生菌根真菌共生的植物功能差异很大,然而其对土壤酸缓冲性能的影响仍知之甚少。本研究以亚热带丛枝和外生菌根森林为对象,比较两种菌根类型森林土壤酸缓冲容量及其相关理化性质的差异。结果表明:丛枝菌根森林土壤酸缓冲容量显著高于外生菌根森林,同时丛枝菌根森林的土壤pH值、交换性盐基总量、阳离子交换量、交换性钾、交换性钠、交换性钙、有机质和硝态氮均显著高于外生菌根森林,铵态氮显著低于外生菌根森林(P<0.05);土壤酸缓冲容量与pH值、有机质、交换性钙、阳离子交换量和盐基饱和度呈极显著正相关(P<0.01),与盐基离子总量、交换性镁呈显著正相关(P<0.05),与交换性酸含量呈极显著负相关(P<0.01);土壤交换性钙含量和有机质含量可以解释土壤酸缓冲容量变化的47.4%。可见,与外生菌根树种相比,丛枝菌根树种能够通过促进土壤中有机质和盐基离子(主要是钙离子)的积累提高其酸缓冲能力。在长期氮沉降地区丛枝菌根树种森林土壤抵抗土壤pH值变化的能力更强。

Soil acid buffering capacity plays an important role in preventing soil acidification induced by fertilization and atmospheric nitrogen deposition,and thus is critical for maintaining soil functioning.Arbuscular mycorrhizal(AM)and ectomycorrhizal(ECM)plants differ greatly in functional traits,but how the differences of their impacts on soil acid buffering capacity are still poorly understood.In this study,forests with dominant tree species associat-ed with AM and ECM fungi in subtropical China were selected,aiming to investigate soil acid buffering capacity and the relevant physicochemical properties of forest soils.The results showed that AM-dominated forest soils had significantly higher soil acid buffering capacity than ECM-dominated forest soils.In comparison,pH,exchangeable base cations,cation exchange capacity,exchangeable K+,Na+,Ca2+,organic matter and nitrate concentrations were significantly higher in AM-dominated forest soils,but ammonium concentrations were lower than ECM-domina-ted forest soils(P<0.01).Soil acid buffering capacity was positively correlated with pH,soil organic matter,exchangeable calcium,cation exchange capacity and base saturation(P<0.01),the exchangeable base cations and exchangeable magnesium(P<0.05),while it was significantly negatively correlated with the exchangeable acid content(P<0.01).In addition,47.4%of the variation in soil acid buffer capacity could be explained by the con-tents of exchangeable calcium and organic matters.Therefore,AM tree species can improve soil acid buffering abili-ty by promoting accumulation of organic matters and exchangeable base cations(mainly Ca2+)in soils.Moreover,AM-dominated forests could prevent soil acidification better than ECM-dominated forests in subtropical regions when exposed to chronic atmospheric nitrogen deposition.