| Under the background of global warming, carbon cycling in terrestrial ecosystems plays an important role in the changes of atmospheric CO2 concentration, and the effect researches of soil carbon cycling in terrestrial ecosystem become more and more deeply and detailed. In the hilly areas, agroforestry is an important method to solve the problems of food product, poverty and protect the environment, and is the important way to solve the shortage of resources, forestry and land conflicts. This experiment based on the research plant form of the hilly area. Several walnuts-herbs compound model were selected as the research object. We studied the dynamic variation of soil respiration and its response to temperature and humidity of the walnuts-herbs compound system. This study in order to understand the characteristics of soil carbon in deferent agro-forestry model in the hilly regions, provide a theoretical basis for further evaluation of ecological benefits of agroforestry system, promote agro-forestry scientific development; and rich the study theory of different land use patterns on soil respiration and its research on the terrestrial carbon cycle and carbon balance.From January 2014 to December 2014, we use the Li-8100 to observe the soil respiration of four kinds of Agro-forestry model in the hilly area of central Sichuan. The four treatments as follows:and study the response of soil respiration to soil temperature and humidity. And study the 24h dynamic of soil respiration in different seasons, and also study the relationship between three soil hydrolytic enzyme, microbial biomass carbon and nitrogen, soil oganic matter and soil respiration.The carbon emissions of soil of compound models in the hilly area of central Sichuan Basin walnut-herbal in about 7.391 a-1 hm-2, control was higher than that of composite model soil carbon emissions, but the difference not significant. The results showed that:the monthly dynamic change of soil respiration of walnuts-herbs treatments composite mode in hilly area increased first and decreased later. The maximum value of walnuts-Chuanmingshen complex pattern occurred in late June is 3.49 μmol m-2 s-1,the peak values of walnuts-Kikyo and walnuts-Agastache soil respiration occurred in July are 3.83 μmol m-2 s-1,4.07 μmol m-2 s-1, 3.86 μmol m-2 s-1. The low values appeared in January, sort the list by CK, C, J, H is 0.36 μmol m-2 s-1,0.49 μmol m-2 s-1,0.58 μmol m-2 s-1, and 0.32 μmol m-2 s-1. The study found that, the Exponential growth relationship between Soil respiration and soil temperature is significantly exponential growth. The difference between three kinds of composite model of soil respiration may cause by different herbs and phenological differences.The Q10 value of Several kinds of walnut-medicinal composite model soil respiration shows Low in summer and high in winter, the maximum value is 4.02 and the minimum is 1.38, the maximum value is about three times as big as the minimum value, and they appeared in the control treatment. The agro-forestry Pattern reduced the sensitivity of soil respiration to temperature, problely due to medicinal plant roots directly or indirectly buffered the effect of changeable temperature on soil respiration.The activity of Urease, Invertase and acid Phosphatase increased first and decrease later from spring to winter, the maximum values of three enzymes appeared in summer (0.0028 μmol g-1 h-1,0.0082 μmol g-1 h-1 and 0.02 μmol g-1 h-1); the minimum value of three Enzymes appeared in winter (0.0005 μmol g-1 h-1,0.0003 μmol g-1 h-1 and 0.0025 μmol g-1 h-1).Repeated measures analysis of variance showed there is no significant difference between urease and invertase, but which between seasonal effect and interaction between season and treatment is significant, the differences between different treatments of Acid phosphatase, seasonal effect and interaction between season and treatment are significant. The relationship between three kinds of hydrolase activity and Soil respiration is significant; different walnut-medicinal composite model has no significant effect on three kinds of hydrolase activities.In the fourth quarter of 2014, only the soil microbial biomass carbon content in winter was significantly lower than that in spring, summer and autumn the soil microbial biomass nitrogen contents showed no significant difference between each composite model and control treatment,the content in summer was significantly higher than that in other three quarters.There is an exponential relationship between the content of soil microbial biomass carbon and nitrogen and soil respiration, and reciprocally related relationship between the content of organic matter and soil respiration, which may due to low soil nutrient in research area.Comparison the walnut plantations and walnut-herbal composite pattern, walnut-herbal composite model has certain effect on reducing carbon emissions in the hilly area of Sichuan, but clear plays the role of different land use patterns of soil carbon in the atmosphere in the carbon cycle, need to carry out a more comprehensive and in-depth quantitative research. |
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