野外模拟酸雨胁迫下接种外生菌根真菌对马尾松幼苗的缓解作用

外生菌根真菌能够提高宿主植物对外界环境胁迫的抵抗力。主要探讨野外条件下外生菌根真菌对酸雨胁迫下马尾松(Pinus massoniana)幼苗生长、养分元素以及表层土壤的影响,以期为酸雨严重区马尾松林恢复提供科学依据。以2年生马尾松幼苗为材料,采用原位试验,共设置6个处理:p H5.6(对照)处理未接种、对照处理接种、p H4.5酸雨处理未接种、p H4.5酸雨处理接种、p H3.5酸雨处理未接种、p H3.5酸雨处理接种。研究表明:(1)酸雨处理与对照处理相比显著降低了非菌根苗总生物量及各部位生物量(根、茎、叶),对株高无显著影响,接种外生菌根真菌可以缓解酸雨对马尾松幼苗生长的不利影响;(2)与对照处理相比,酸雨处理的非菌根苗的针叶中N、P、Ca含量升高,Mg含量降低,根系中N、P、Ca含量降低,Mg含量随p H的降低先升高后降低。接种外生菌根真菌显著提高了p H3.5酸雨处理的马尾松幼苗根系中N、P、Ca、Mg含量,而对针叶中N、P、Ca、Mg含量无显著影响。(3)在非菌根土壤中,p H3.5酸雨处理与对照处理相比显著降低了土壤中有机质、速效磷、速效钾、可溶性碳、可溶性氮、铵态氮、硝态氮含量,而接种外生菌根真菌显著提高了上述指标。酸雨对土壤阳离子交换量无显著影响。总而言之,接种外生菌根真菌促进了酸雨处理的马尾松幼苗生长、缓解了酸雨对马尾松幼苗养分元素和表层土壤的不利影响,由此可见接种外生菌根真菌是减轻酸雨对马尾松危害的一个重要途径。

Effects of ectomycorrhizal fungi on seedlings of Pinus massoniana under simulated acid rain

Many tree species in forest ecosystems have symbiotic relationships with ectomycorrhizal fungi (ECM), which protects their hosts from environmental stress. Effects of ECM on growth, elemental nutrients, and rhizosphere soil of Pinus massoniana seedlings under simulated acid rain were analyzed in this study to provide a scientific basis for restoration of P. massoniana in an area with severe acid rain in China. Two-year-old seedlings of P. massoniana were grown in forest soil from one of six treatments, including pH 5.6 (CK) inoculated with ECM, CK without ECM, pH 4.5 inoculated with ECM, pH 4.5 without ECM, pH 3.5 inoculated with ECM, and pH 3.5 without ECM. The results showed that:(1) For the P. massoniana seedlings grown in soil not inoculated with ECM, the acid rain treatments significantly reduced leaf area, total biomass, and biomass of roots, stems, and needles, whereas plant height did not differ from that of plants grown in CK. Inoculation with ECM removed the negative effects of acid rain on growth. (2) For the P. massoniana seedlings grown in soil without ECM, the N, P, and Ca content was higher in needles and decreased in roots in the acid rain treatments than those of plants grown in CK. The content of Mg decreased in needles in acid rain treatments, whereas it increased at first and then decreased in roots with a decrease in pH with respect to that of plants grown in CK. Inoculation with ECM significantly increased N, P, Ca, and Mg content of roots; however, there was no effect on N, P, Ca, and Mg content of the needles in the pH 3.5 treatment. (3) For plants grown in soil without ECM, pH 3.5 treatment decreased the content of soil organic matter, available P, available K, soluble carbon, soluble nitrogen, nitrate nitrogen, and ammonium nitrogen, but inoculation with ECM improved soil quality. Acid rain treatments did not significantly affect the cation exchange capacity. These results indicated that inoculation with ECM could stimulate growth of P. massoniana seedlings and effectively alleviate adverse effects on nutrients and rhizosphere soil of P. massoniana seedlings caused by acid rain. Therefore, inoculation with ECM could be an effective way to decrease the hazard of acid rain to Pinus massoniana.