[Effects of simulated nitrogen deposition on soil respiration in northern subtropical deciduous broad-leaved forest].

To investigate the effects of elevated nitrogen deposition on forest soil respiration, a simulated nitrogen deposition field experiment was conducted in northern subtropical deciduous broad-leave forest from April 2008 to April 2009. Nitrogen treatments included the control (no N addition, CK), low-N [50 kg x (hm2 x a)(-1), T(L)], medium-N [100 kg x (hm2 x a)(-1), T(M)], and high-N [150 kg x (hm2 x a)(-1), T(H)]. The respiration rates were measured by a static chamber-gas chromatograph method. Results showed that nitrogen deposition did not change the seasonal and daily variation patterns of soil respiration. Compared to the control, T(L), T(M) and T(H) treatments reduced soil annual average respiration rates by 8.51%, 9.74% and 11.24%, respectively. Meanwhile, T(L), T(M) and T(H) treatments decreased daily average soil respiration rates by 4.42%, 11.09% and 12.17%, respectively. Significant relationship was found between soil respiration rate and soil temperature. The Q10 (temperature sensitivity coefficients) for soil respiration of CK, T(L), T(M), and T(H) treatments were 2.53, 3.22, 2.64 and 2.92, respectively. Our findings suggested that nitrogen deposition reduced soil respiration, and increased soil respiration temperature sensitivity in northern subtropical deciduous broad-leave forest.