The Impact Of Simulated Nitrogen Deposition On Soil Microbia In Sub-tropical Plantation

Nitrogen deposition can influence the growth and reproduction of the soil microbes, change the community structure and function, influence the soil material transformation and nutrient availability of soil microbial. it can offer a reference for sustainable development of forest ecological system to study nitrogen deposition on soil microflora, microbial organic C,N and community metabolism ability. This study showed the responses of the change of soil microbial quantity, organic carbon and organic nitrogen of soil microbial and metabolism ability of soil microbial community in cinnamomum camphora and Pinus elliottii plantation at four N addition levels:To(0g NH4NO3/m2), T1(5g NH4NO3/m2),T2(15g NH4NO3/m2),T3(3Og NH4NO3/m2). The following are the main achievements obtained in our experiment:1. The response of soil microbial flora to nitrogen depositionTwo kinds of forest soil microorganism quantity response to simulated nitrogen deposition keep consistent. T1inhibiting the growth of microorganisms, T2and T3promoted the growth of microorganisms. Among them, on cinnamomum camphora forests, nitrogen promoted the growth of bacteria, inhibiting the growth of actinomycetes and fungus; on pinus elliottii forests, nitrogen promoted the growth of bacteria and fungi, but no effect of actinomycetes.2.The influence of nitrogen deposition on organic carbon of soil microbial and organic nitrogen of soil microbialUnder influence of nitrogen deposition,2kinds of forest soil microbial organic carbon were inhibit, the higher nitrogen concentration the more inhibition.The inflation of organic nitrogen of cinnamomum camphora forests soil microbial is after9month of simulated nitrogen deposition showed a marked suppression; on pinus elliottii forests, the organic nitrogen of soil microbial are significant growth on T2level, T3level is less than T2level and no effect on T1level.After nitrogen deposition1year, the carbon-nitrogen ratio of two kinds of forest is increases. The reason of cinnamomum camphora forests carbon-nitrogen ratio increases due to organic nitrogen of soil microbial decreased; the reason of pinus elliottii forests carbon-nitrogen ratio increases because of the increase of the increase of organic carbon and the decrease of organic nitrogen.3. The influence of nitrogen deposition on soil microbial metabolic capacityApplication of BIOLOG method to test the nitrogen after adding microbial community metabolism ability, the results showed that T3level promotes microbial community metabolism ability of cinnamomum camphora forests, T1and T2no effect on it; on pinus elliottii forests, T1,T2and T3levels all promote microbial community metabolism ability.Based on the ability difference of soil microbial community metabolism ability, using the Shannon index, Simpson index and Mclntosh index to analyze the diversity of microbial. The results showed that two types of forest soil microbial diversity increased with the nitrogen concentration increased.