大兴安岭重度火烧迹地恢复后土壤磷形态与解磷细菌分布特征

Soil phosphorus forms and phosphorus solubilizing bacteria distribution after restoration from seriously burning in Greater Khingan Mountain areas, China

为了探讨大兴安岭重度火烧迹地恢复后土壤不同磷形态含量、解磷细菌群落结构的差异及两者之间的关系,以人工恢复(樟子松人工林、落叶松人工林)、人工促进天然恢复(次生林)以及天然恢复(天然次生林)的林地土壤为研究对象,采用Sui等修正的Hedley磷素分级法对根际土壤和0~10、10~20 cm非根际土壤进行磷素分级测定,并用高通量测序法得到土壤解磷细菌种群丰度。结果表明:0~10 cm非根际土壤水溶性磷(H2O-Pi)、碳酸氢钠无机磷(NaHCO3-Pi)、碳酸氢钠有机磷(NaHCO3-Po)及根际土壤NaHCO3-Po含量表现为落叶松人工林>樟子松人工林>天然次生林>次生林。10~20 cm非根际土壤H2O-Pi、NaHCO3-Pi、NaHCO3-Po及根际土壤H2O-Pi、NaHCO3-Pi含量表现为落叶松人工林>樟子松人工林>次生林>天然次生林。不同林分根际与非根际土壤H2O-Pi、NaHCO3-Pi和NaHCO3-Po含量的比值(R/S)均大于1。中等活性氢氧化钠磷(NaOH-P)包括氢氧化钠无机磷(NaOH-Pi)和氢氧化钠有机磷(NaOH-Po)。在0~10 cm非根际土壤及根际土壤中NaOH-P含量表现为落叶松人工林>天然次生林>次生林>樟子松人工林,在10~20 cm非根际土壤中表现为落叶松人工林>樟子松人工林>次生林>天然次生林。土壤NaOH-P存在明显的根际效应。酸溶性磷(HCl-P)包括酸溶性无机磷(HCl-Pi)和酸溶性有机磷(HCl-Po)。在0~10 cm非根际土壤中HCl-P含量表现为落叶松人工林>天然次生林>樟子松人工林>次生林,在10~20 cm非根际及根际土壤中表现为落叶松人工林>樟子松人工林>天然次生林>次生林。土壤残留磷(residual-P)含量对林地恢复方式不敏感。各林分土壤主要解磷细菌均为慢生根瘤菌属、链霉菌属、伯克霍尔德菌属和芽孢杆菌属。樟子松人工林和落叶松人工林土壤解磷细菌丰度显著高于次生林和天然次生林。冗余分析表明,解磷细菌与不同磷形态之间相关性各异。在现阶段来看,人工恢复更有利于提高土壤磷的有效性和增加解磷细菌的丰度。

To understand the contents of various phosphorus forms, phosphorus solubilizing bacte-rial community structure and the relationship between them in soils after restoration from the seriously burning, we collected soil samples from artificial restoration(Pinus sylvestris var. mongolica plantation, Larix gmelinii plantation), artificial accelerated natural restoration(secondary forest) and natural restoration(natural secondary forest) stands in Greater Khingan Mountain area. Using methods of Sui et al. modified from Hedley phosphorus fractionation, we measured the contents of different phosphorus forms in rhizosphere soil and bulk soil(0-10, 10-20 cm). Abundances of phosphorus solubilizing bacteria were quantified by high-throughput sequencing method. The results showed that the contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Po in 0-10 cm bulk soil and NaHCO3-Po in rhizosphere soil followed the order of L. gmelinii plantation > P. sylvestris var. mongolica plantation > natural secondary forest > secondary forest. The contents of H2O-Pi, NaHCO3-Pi, NaHCO3-Po in 10-20 cm bulk soil and H2O-Pi, NaHCO3-Pi in rhizosphere soil followed the order of L. gmelinii plantation > P. sylvestris var. mongolica plantation > secondary forest > natural secondary forest. The ratios of contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Po in rhizosphere to those in bulk soil(R/S) were higher than 1 in all forest stands. The moderately labile NaOH-P included NaOH-Pi and NaOH-Po. The content of NaOH-P was in order of L. gmelinii plantation > natural secondary forest > secondary forest > P. sylvestris var. mongolica plantation in 0-10 cm layer of bulk and rhizosphere soil, and ranked as L. gmelinii plantation > P. sylvestris var. mongolica plantation > secondary forest > natural secondary forest in 10-20 cm layer of bulk soil. There was rhizosphere effect of NaOH-P in the soil. The stable HCl-P included HCl-Pi and HCl-Po. The content of HCl-P followed the order of L. gmelinii plantation > natural secondary forest > P. sylvestris var. mongolica plantation > secondary forest in 0-10 cm layer of bulk soil,and ranked as L. gmelinii plantation > P. sylvestris var. mongolica plantation > natural secondary forest > secondary forest in the 10-20 cm layer. The content of residual-P in the soil was not sensitive to restoration methods. Bradyrhizobium, Streptomyces, Burkholderia and Bacillus were the main phosphorus solubilizing bacteria across all forest stands. The abundances of phosphorus solubilizing bacteria in soil of L. gmelinii plantation and P. sylvestris var. mongolica plantation were significantly higher than that of secondary forest and natural secondary forest. Results of redundancy analysis showed that the correlation between phosphorus solubilizing bacteria and various phosphorus forms was different. Our results showed that artificial afforestation was more conducive in improving the availability of phosphorus in soil and the abundance of phosphorus solubilizing bacteria.