除草剂对桉树人工林下植物及土壤微生物群落的影响

除草剂在桉树人工林中的应用越来越普遍，但关于除草剂对桉树人工林林下植物和土壤微生物群落的影响知之甚少。通过桉树人工林低剂量高频率（LHF）、中剂量中频率（MMF）、高剂量低频率（HLF）除草剂喷施试验，并与人工除草（MT）为对照，比较分析不同剂量、不同频率除草剂施用对林下植物和土壤微生物群落的影响。结果表明，施用除草剂导致桉树人工林林下植物种类和功能群组成发生显著变化，但并未显著降低林下植物群落物种丰富度和多样性，随除草剂施用频率的降低及恢复时间的增加，物种丰富度及多样性指数呈恢复趋势。除草剂施用也导致土壤养分含量降低。除草剂通过对林下植物群落和土壤养分的负面影响间接影响土壤微生物群落。LHF显著降低藤本植物而显著提高蕨类植物功能群的重要值，从而显著降低了微生物群落、真菌和放线菌的磷脂脂肪酸（PLFA）含量。MMF显著降低木本和藤本植物而显著提高禾草植物功能群的重要值，导致土壤微生物群落和放线菌的PLFA含量显著降低。HLF未显著影响林下植物及土壤微生物群落，但土壤全磷含量显著降低，速效磷含量也大幅下降。施用除草剂显著降低了土壤微生物生物量碳、氮的含量。因此，生产上应减少除草剂的施用，以减少对林下植物和土壤微生物群落的负效应。

Effects of herbicide on understory plant and soil microbial communities in Eucalyptus plantations

Herbicides have been widely used in Eucalyptus plantations, but little is known about the effects of herbicides on understory plant and soil microbial communities in Eucalyptus plantations. This study compared and analyzed the effects of herbicide application at different dosages and frequencies on understory plant and soil microbial communities through application experiments with low-dose high-frequency (LHF), medium-dose medium-frequency (MMF), and high-dose low-frequency (HLF) herbicides and comparison with manual tending (MT) in Eucalyptus plantations. The results showed that herbicide application resulted in significant changes in understory plant species and functional group composition in Eucalyptus plantations. However, herbicides did not significantly reduce the species richness or diversity of understory plant communities, but decreasing the herbicide application frequency and increasing the recovery time led the species richness and diversity index to show a trend of recovery. Herbicide application also results in a decrease in soil nutrient contents. With the increase of herbicide concentration and the decrease of herbicide frequency, the soil pH and total potassium concentration showed a trend of increasing, the soil water content, available phosphorus and available potassium concentrations showed a trend of decreasing, but the concentrations of soil organic matter, total nitrogen and available nitrogen showed a trend of decreasing first and then increasing. Herbicides indirectly affected soil microbial communities through their negative effects on understory plant communities and soil nutrients. LHF significantly reduced the importance value of the vine functional group while significantly increased that of the fern functional group, thus significantly reduced the phospholipid fatty acid (PLFA) content of the microbial community, fungi, and actinomycetes. MMF significantly decreased the importance value of the woody and vine functional groups but significantly increased the Gramineae plant functional group, leading to a significant decrease in the PLFA content of the microbial community and actinomycetes. HLF did not significantly affect the understory plant or soil microbial communities but significantly reduced both the soil total phosphorus concentration and the soil available phosphorus content. Meanwhile, herbicide significantly reduced the soil microbial biomass carbon and nitrogen content. Therefore, the application of herbicides should be decreased to reduce the negative effects on understory plant and soil microbial communities.