Soil respiration and its environmental response varies by day/night and by growing/dormant season in a subalpine forest

Comparisons of soil respiration (R(S)) and its components of heterotrophic (R(H)) and rhizospheric (R(R)) respiration during daytime and nighttime, growing (GS) and dormant season (DS), have not being well studied and documented. In this study, we compared R(S), R(H), R(R), and their responses to soil temperature (T(5)) and moisture (θ(5)) in daytime vs. nighttime and GS vs. DS in a subalpine forest in 2011. In GS, nighttime R(S) and R(H) rates were 30.5 ± 4.4% (mean ± SE) and 30.2 ± 6.5% lower than in daytime, while in DS, they were 35.5 ± 5.5% and 37.3 ± 8.5% lower, respectively. DS R(S) and R(H) accounted for 27.3 ± 2.5% and 27.6 ± 2.6% of GS R(S) and R(H), respectively. The temperature sensitivities (Q(10)) of R(S) and R(H) were higher in nighttime than daytime, and in DS than GS, while they all decreased with increase of T(5). Soil C fluxes were more responsive to θ(5) in nighttime than daytime, and in DS than GS. Our results suggest that the DS and nighttime R(S) play an important role in regulating carbon cycle and its response to climate change in alpine forests, and therefore, they should be taken into consideration in order to make accurate predictions of R(S) and ecosystem carbon cycle under climate change scenarios.