Effects Of Prescribed Burning And Herbicide Application On Plant Diversity In Understory And Soil Microbial Diversity In Mixed Eucalyptus × D. Odorifera Plantations

Plantation forests play an important role in ensuring the safety of timber production and mitigating the global climate change. China is the largest forest plantation area country in the world.This study carried out an experiment including 4 kinds of treatments, including prescribed burning (BF), herbicide application (HF), prescribed burning combined herbicide application (BHF) and control (no burning and herbicide, CK) in a mixed Eucalyptus × D. odorifera plantation in southern China. The effects of different treatments on plant diversity, functional groups in understory and soil microbial diversity was assessed by community survey and phospholipid fatty acid (PLFA) mapping method. The objective is to clarify the effects of prescribed burning and herbicide application on plant diversity in understory and soil microbial diversity in mixed Eucalyptus x D. odorifera plantations, and provide reference for the sustainable management of.Eucalyptus plantation forests.The main results are as follows:(1) Compared with the control (CK), burning and herbicide treatmentsignificantly improved the species richness and a diversity of herb layers, reduced species richness anda diversity of shrub layers, but the difference was not significant. Burning and herbicide treatment significantly increased the total number of individuals, but had no significant effect on other diversity index of shrub plants. Moreover, burning and herbicide treatment significantly increased the species richness and ecological dominance and decreased a diversity of herbaceous species. Burning, herbicide, or their combination can significantly change the composition and structure of understory vegetation.(2) Compared with the control (CK), burning treatment had no significant influence on the richness, relative abundance and relative coverage of plant functional groups in understory. Herbicide application treatment significantly decreased the richness of the woody plant functional groups and the relative abundance of woody and leguminous plant functional groups, but significantly improved the relative coverage of the ferns and woody plant functional groups.(3) Compared with the control (CK), burning, herbicide, and burning combined herbicide treatment improved soil microbial biomass. The burning combined herbicide treatment had the most significant effects. Burning treatment significantly increased the bacteria, gram-positive bacteria and gram-negative bacteria community biomass of soil microbial in the mixed forest. Herbicide treatment significantly increased the bacteria, gram-positive bacteria, gram-negative bacteria and arbuscular mycorrhizal fungi bacteriacommunity biomass of soil microbial in the mixed forest. Burning and herbicide mixed treatment significantly increased the bacteria, gram-positive bacteria, gram-negative bacteria and arbuscular mycorrhizal fungi bacteria community biomass of soil microbial in the mixed forest.(4) Burning, herbicide treatment alone or their combined treatment significantly reduced the phospholipid fatty acids relative percentage of protozoa in soil microbial in the mixed forest. But burning and herbicide mixed treatment significantly increased the phospholipid fatty acids relative percentage of bacteria in the soil microorganisms in the mixed forest. The species richness of understory plant and microbial biomass of 0～10 cm soil layer were positive correlation, but not closely related.