| Soil respiration (Rs) is the process that soil releases CO2 to atmosphere (also called soil surface CO2 flux), and is the important part of carbon cycling in terrestrial ecosystems. Soil respiration includes plant root respiration, soil microbial and fauna respiration. The respiration and the variation mechanism of the three components will be direct response to the intensity of soil respiration and will affect plant growth and ecosystem carbon balance. Thus separate and quantify the different components (root respiration, soil microbial and fauna respiration) of soil respiration is critical to learn the carbon cycling of forest ecosystem and is the focal point in current. In this study, using infrared gas exchange analyzer (Li-Cor-8100), we combined with trench method excluded roots, naphthalene combining with electric bar(220V) exclude soil faunas measuring the soil respiration and its three biological processes (root respiration, soil microbial respiration and fauna respiration) from spatial and temporal scale in Mao bamboo plantations. Soil temperature, moisture, the biomass of he microbe, root and fauna were measured at the same time. Main objective was to estimate the contribution of root respiration, soil microbial and soil fauna respiration to soil respiration and determine the control factor of the total soil respiration and the respiration from different components, the results showed that:(1)Total soil respiration and the three components at the three elevations had similar diurnal variation trend (single peak curve) with those of air temperature and soil temperature. The minimum values always occurred at 02:00 at night, neither did the maximum values. Total soil respiration peaked in the afternoon around 15:00, root respiration peaked at 11:00, both soil microbial respiration and fauna had gentle diurnal variation and the maximum occurred at 11:00-15:00. Seasonal variation showed that total soil respiration and the three components respiration consistent with soil temperature and air temperature, had a maximum in 7-8 months and minimum in 11-12 months. Spatial variation showed that soil respiration, root respiration and microbial respiration reduced with elevation increased, while fauna respiration had the maximum at 200m altitude,400m had the smallest respiration. The reasons for this spatial variability are due to soil temperature and humidity, the biological factors (roots, microbes and animal biomass) and soil factors.(2)The average daily respiration of the total CO2 efflux of 200m,400m and 700m altitude varied from 3.89μmol·m-2·s-1 to 5.49μmol·m-2·s-1 in August 2008 and 3.36μmol·m-2·s-1-4.05μmol·m-2·s-1 in August 2009. During the periods from Mar to Dec in 2008 the average annual respiration of this three elevations was 3.10μmol·m-2·s-1-3.60μmol·m-2·s-1,2009 years was 2.58μmol·m-2·s-1-3.12μmol·m-2·s-1. Carbon (C) flux were 881.61 gC m-2-1028.35 g C m-2 in 2008, increased 12.74%-18.03% than in 2009 and in the range in tropical and subtropical forest (345 gC m-2 a-1-1520 gC m-2 a-1).The daily contribution rate of root respiration to total soil respiration was 51.73%-55.53% and annual contribution rate was 33.51%-38.90% in 2008, while in 2009 the daily contribution rate was 44.95%-48.97% and annual contribution rate was 34.79%-41.89%.200m altitudes had the highest root respiration contribution,700m was the minimum. Different regions, ecosystems and methods all had an impact on root respiration. C flux from root respiration during Mar to Dec varied between 323.93 g C m-2-431.48 g C m-2, accounting for 36.74%-41.96% of the total C flux in 2008; C flux varied from 277.24 g C m-2-401.25 g C m-2, accounting for 37.05%-44.70% of total soil respiration in 2009; 200m altitude had the largest C flux and more 3.40% than 400m and 14.20% than 700m.The daily contribution rate of heterotrophic respiration(microbial respiration, fauna respiration) to total soil respiration of 200m,400m and 700m varied from 42.85%-47.87%(of which microbial respiration was 35.31%-39.45%, fauna respiration was 7.54%-8.42%) in 2008; while in 2009, the contribution rate was 52.34%-53.43%(of which microbial respiration was 45.42%-45.52%,6.92% animal breathing 7.91%). The annual contribution rate of heterotrophic respiration of the three altitudes were 59.02%-65.36%(of which microbial respiration was 52.07%-57.67%, fauna respiration was 6.95%-7.69%),2009 was 54.60%-64.86%(of which microbial respiration was 47.41%-57.04%, fauna respiration was 7.19%-7.82%). C flux from heterotrophic respiration during Mar to Dec was 557.68-626.63 g C m-2, accounting for 57.36%～63.93% of total C flux (of which soil fauna respiration was 69.42 g C m-2-87.94 g C m-2, accounting for 7.87%-8.55% of total soil respiration, microbial respiration was 488.26 g C m-2-544.75 g C m-2, accounting for of total soil respiration 49.49%-55.38%) in 2008; while in 2009, C flux from heterotrophic respiration was 470.9 g C m-2-500.93 g C m'2, accounting for 55.12%-63.63%of total soil respiration (fauna respiration was 60.81 g C m-2-74.57 g C m-2, accounting for 8.13%-8.81% of total soil respiration, microbial respiration was 410.18 g C m-2-429.12 g C m-2, accounting for 46.99%-54.82% of total soil respiration).Heterotrophic respiration are the main components of soil surface CO2 flux.C flux from root respiration was 195.15 g C m-2-233.75 g C m-2 smaller than heterotrophic respiration in 2008 and 99.65 g C m-2-193.66 g C m-2 in 2009.(3)The correlation between soil temperature and total soil respiration, soil microbial respiration and soil fauna respiration is significant exponent function(P<0.01). The relationship between total soil respiration and soil temperature at different depth (soil surface,0-10cm,10-20cm and 20-30cm) reached a significant level (P<0.05) and the correlation with soil temperature at 10cm depth reached the very significant level (P<0.01). Soil microbial respiration had higher Q10 than root respiration, while compared with microbial respiration, the relationship between soil fauna respiration and soil temperature was slightly, but Q10 values bigger than Q10 of root and microbial respiration.Compared with the correlation between soil temperature and soil respiration, the correlation between soil respiration and soil water content was less apparent, but there was an apparent improvement in the correlation between standardized soil respiration (Rio) and soil water content(P<0.05) when the effect of soil temperature was removed. Soil water content had significant effect on root respiration and had very significant linear correlation (P<0.01), but the relationship between soil water content and fauna, microbial respiration was not significant.Compared with the one-dimensional (soil temperature and soil water content) equation, the R2 of the two-dimensional equation increased to some extent. The combination effect of soil temperature and soil water content could explained more 50% of soil respiration at different altitudes, root respiration could explained 77.1%-90.3%, soil microbial respiration explained 86.5%-88.9% and soil fauna explained 68.3%-76.2%, indicating that soil respiration and its components are affected by both soil temperature and soil water content in Mao bamboo forest in subtropical.Microbial respiration showed a significantly positive correlation with the biomass of bacteria, actinomycetes (P<0.01) and microbial biomass C (P<0.05), while had no correlation (P>0.05) with fungi. Biomass of root and soil fauna components can also lead to differences in soil respiration, live underground root biomass could explain 65%-70% of soil respiration. The total numbers of the soil faunas could explained 55.4%-60.1% of soil respiration in Mao bamboo forest(4) The total soil respiration of health, general health, sub-health and poor healthy Mao bamboo forest were healthy forest>the general healthy forest>sub-health forest>poor healthy forest and there was very significant difference between them (P< 0.01). Contribution of soil microbial respiration were health forest>general healthy forest>Sub-health forestpoor healthy forest; root respiration contribution rate was sub-health forest>health forest>general healthy forest>poor healthy forest; contribution of soil fauna respiration rate was healthy forest>general healthy forest>sub-health forest>poor healthy forest.
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