| Soil respiration is the main way of soil organic carbon loss,and litter decomposition is the main source of soil organic carbon input.Both are very important components in the carbon cycle of forest soil.Phyllostachys edulis is one of the main types of forest in China.It has the characteristics of wide distribution,fast growth and strong carbon fixation,which plays an important role in regulating the atmospheric CO2.Strengthen the Moso bamboo forest soil respiration and litter decomposition characteristics and influencing factors of research,help to reveal the soil carbon cycle key process of the main control factors,for the region of moso bamboo forest sustainable management and provide theoretical basis for improving bamboo forest soil carbon reserves.Soil organic carbon quality often reflects the availability of soil organic carbon.The chemical structure of soil organic carbon is the common method used to characterize the quality of soil organic carbon.In addition,as the main driving factor of soil organic carbon decomposition,soil microbial community structure and function?enzyme activity?are the important basis for studying soil organic carbon decomposition.In this study,through the field observation of soil respiration and its components in the typical bamboo forest in South Sichuan,the total soil respiration of the bamboo forest was influenced by the determination of soil temperature and humidity,soil physical and chemical properties,litter and fine root characteristics,soil organic carbon and carbon chemical structure,soil microbial community structure and function.The bioenvironmental factors of each component reveal the effects of biological and abiotic factors on soil respiration in Moso bamboo fores.?1?0-5cm soil organic carbon structure showed the highest aromatic carbon,followed by oxygen alkyl carbon,and alkyl carbon and carbonyl carbon.Biological and abiotic factors significantly affect soil organic carbon and carbon chemical structure,in which soil organic carbon is related to total nitrogen,nitrate nitrogen,total phosphorus,capillary porosity,non capillary porosity and soil water content.The soil physical and chemical factors mainly influence soil organic carbon through indirect effects,and litter biomass at the same time.And the chemical properties of fine roots are also key factors affecting soil organic carbon;in addition,fungi,Gram-negative bacteria are associated with aromatic carbon,capillary porosity is related to oxygen alkyl carbon,non capillary porosity,soil bulk density,fine root nitrogen and phosphorus ratio,fungi and Gram-negative bacteria related to alkyl carbon,pH,fungi and Gram-negative bacteria related to carbonyl carbon.?2?In order to understand the process of litter decomposition and its influencing factors,an important soil carbon process in Moso bamboo forest in South Sichuan has been carried out.In view of the important influence of litter quality and forest type on decomposition,two kinds of leaf and fine root,which have the most distinct quality differences,have been tested in different places.It was found that the decomposition rate of the leaf and root of bamboo and Dicranopteris pedata was significant,and the annual decomposition coefficient?k?of litter?0.73±0.02?was higher than that of bamboo?0.58±0.03?,while the annual decomposition rate?k?of fine root?0.66±0.04?was higher than that of Dicranopteris pedata?0.42±0.03?,and C,N and P in the leaves and fine roots of the litter were all the net release patterns of nutrients.The mixed decomposition of Phyllostachys edulis and Dicranopteris pedata leaf litter?or fine root?did not produce a mixing effect,but significantly inhibited the release of N and P nutrients from the litter leaves and the release of C from the fine roots;the forest with different coverage of the understory vegetation had a significant influence on the decomposition rate,The annual average decomposition rate of leaf litters of Phyllostachys edulis and Dicranopteris pedata in forest lands with high coverage of undergrowth was 18.75%and 9.10%faster than those in undergrowth forest cover,respectively,and the annual average decomposition rate of fine roots was faster 10.14%and 24.49%;Initial nutrient concentration is a key factor affecting nutrient release patterns and release rates.?3?The annual average rate of soil respiration,heterotrophic respiration and rhizospheric respiration of the bamboo forest in this area were 4.69?mol·m-2·s-1,1.67?mol·m-2·s-1 and2.58?mol·m-2·s-1 respectively.The annual cumulative flux was 4622.15g·m-2,2724 g·m-2 and1898.15 g·m-2.In seasonal dynamics,the contribution rate of rhizospheric respiration and the change trend of surface 5cm soil temperature were the same,and the annual average contribution rate of soil respiration was relatively high?60.57%?.The total soil respiration rate and each component showed significant seasonal dynamics,and the soil temperature showed a significant exponential relationship with the surface 5cm soil temperature.Soil temperature could explain the 56.4%-80.9%of soil respiration variation.It was the main environmental factor of soil respiration and seasonal variation of its components in the study area.There was no significant correlation between soil moisture and soil respiration.The temperature sensitivity?Q10?of different respiratory components was rhizospheric respiration?3.38?>heterotrophic respiration?2.21?.The effects of biological or abiotic factors on soil total respiration and each component respiration are different.Total soil respiration is significantly related to capillary porosity,non capillary porosity and fine root biomass.The soil rhizospheric respiration is related to capillary porosity,non capillary porosity and fine root biomass,and is related to the content of fine root nitrogen and phosphorus.The heterotrophic respiration is mainly influenced by the C/N of fine roots.?4?0-5cm soil microbial community was the highest in the soil microbial community,accounting for 75.65%of the total soil biomass,while actinomycetes and fungi accounted for16.43%and 3.63%of the total.Seasonal dynamics significantly affected soil microbial biomass and soil enzyme activity.RDA analysis showed that soil temperature and NH4+-N are the main environmental factors affecting soil microbial community structure,and can explain34%of the variation of soil microbial community structure.Total nitrogen and arbuscular mycorrhizal fungi are the main abiotic and biological factors affecting soil enzyme activity.It can release 70%and 28%of the function variation of soil microbes respectively.In addition,there were differences in soil microbial community structure and soil enzyme activity among different plantations with different vegetation coverage.The main manifestations were the differentiation of arbuscular mycorrhizal fungi,actinomycetes,?-glucosidase,protease and phenol oxidase.?5?Soil respiration is affected by environmental factors,chemical structure of soil organic carbon,litter and fine root properties,soil microorganism and other biological and abiotic factors.RDA analysis showed that the non capillary porosity and capillary porosity were the most important environmental factors affecting the variation of soil respiration,which could explain 77.9%of the respiratory variation,in which total respiration and rhizospheric respiration were significantly positively correlated with non capillary porosity,and negatively correlated with capillary porosity;fungi and fine root biomass were affected by soil respiration.The main biological factors of the variation are that the total respiration and the rhizospheric respiration are positively related to the fine root biomass,and the heterotrophic respiration is negatively correlated with the fungi,and the alkyl carbon/oxygen alkyl carbon ratio in the soil organic carbon chemical structure can explain 36.7%of the total soil respiration and heterotrophic respiration. |
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