Short-term effects of nitrogen deposition on soil respiration of Cinnamomum camphora plantation

The nitrogen deposition experiments on Cinnamomum camphora plantation of Hunan provincial botanical garden were simulated from June the 7th to October the 7th 2010,the nitrogen deposition levels was respectively as control(CK,0 g·m-2 a-1),low nitrogen(LN,5 g·m-2 a-1),medium nitrogen(MN,15 g·m-2 a-1) and high nitrogen(HN,30 g·m-2 a-1).The soil respiration speed and soil surface temperature and the surface water content of the soil were determined by LI-8100 measuring instrument.The results show that the average values of soil respiration speed were CK(4.09±0.66 μmol·m-2 s-1),LN(2.39±0.29 μmol·m-2 s-1),MN(2.18±0.19 μmol·m-2 s-1),HN(2.28±0.25 μmol·m-2 s-1),that of the CK was obviously higher than the other three treatments(P0.01).With different nitrogen concentrations deposition treatments,the Q10(temperature sensitivity coefficients) for soil respiration of CK,LN,MN and HN treatments were 1.84,1.71,1.83 and 1.56.It was positive correlation between the respiration speed and the surface(≤10 cm) temperature of tested soil.It was negative correlation between the respiration speed and the surface(≤5 cm) water content of tested soil(P0.05).Volumetric water content of 5 cm soil was between 0.266 6～0.294 4(m3·m-3),it did not vary much monthly during the research period(1.8%～9.4%).The findings suggest that the initial stage of nitrogen deposition obviously influenced the soil respiration of Cinnamomum camphora plantation.