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

Abstract

Comparisons of soil respiration (RS) and its components of heterotrophic (RH) and rhizospheric (RR) respiration during daytime and nighttime, growing (GS) and dormant season (DS), have not being well studied and documented. In this study, we compared RS, RH, RR, and their responses to soil temperature (T5) and moisture (θ5) in daytime vs. nighttime and GS vs. DS in a subalpine forest in 2011. In GS, nighttime RS and RH 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 RS and RH accounted for 27.3 ± 2.5% and 27.6 ± 2.6% of GS RS and RH, respectively. The temperature sensitivities (Q10) of RS and RH were higher in nighttime than daytime, and in DS than GS, while they all decreased with increase of T5. Soil C fluxes were more responsive to θ5 in nighttime than daytime, and in DS than GS. Our results suggest that the DS and nighttime RS 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 RS and ecosystem carbon cycle under climate change scenarios.

Day–night discrepancy in soil respiration varies with seasons in a temperate forest

“…The higher Rs day than Rs night in autumn corroborates similar findings in a seasonal dry temperate rainforest (Jassal et al, 2007), a longleaf pine wiregrass savanna (Ford et al, 2012) and a subalpine forest (Hu et al, 2016). In addition to the stimulation of higher temperatures in daylight on microbial activity and photosynthesis rate (Carey et al, 2016;Ford et al, 2012;Shi et al, 2006), another possible reason is that the proportion of litter-associated respiration to total Rs in autumn increases owing to the light dependency of the litter component (Zimmermann et al, 2009) and contributes to higher soil CO 2 flux during daytime than during nighttime.…”

“…Different from other studies utilizing a fixed timeslot to classify day and night throughout the year, for example, 7 am to 6 pm as daytime and 7 pm to 6 am as nighttime (Gómez-Gener et al, 2021;Gutiérrez del Arroyo & Wood, 2020;Hu et al, 2016), we used photosynthetically active radiation (PAR; 50Y; Vaisala, Helsinki, acquired above the canopy near the top of the tower) to classify the daytime (PAR >0 μmol m −2 s −1 ) and nighttime (PAR = 0) periods (Yang et al, 2009), which could minimize uncertainty and bias in estimating Rs day and Rs night .…”

“…Conceptually, the variation of Rs within a day is mainly determined by the interactions of biophysical factors, for example, soil moisture (Davidson et al, 2000), precipitation (Rochette et al, 1991), biomass, plant species composition and phenology conditions (Wang, Liu, et al, 2014), but especially influenced by soil temperature (Carey et al, 2016; Hirano, 2005; Makita et al, 2018; Mo et al, 2005). Many studies reported that Rs was higher during the day (Rs day ) than at night (Rs night ), attributed to the diel variation of soil temperature (Ford et al, 2012; Hu et al, 2016; Jassal et al, 2007; Shi et al, 2006). Some researchers suggested that the extrapolated daily Rs from daytime Rs would be overestimated, attributed to the asymmetric diel pattern of soil temperature and higher temperature in daytime (Liang et al, 2004; Shi et al, 2006).…”

“…A number of studies involving Rs temperature sensitivity suggest that Q 10 varies with time and space (Carey et al, 2016; García‐Palacios et al, 2021). However, debates have long prevailed on whether Q 10 differs between day and night, and previous studies observed inconsistent and contradictory results of Q 10 for daytime and nighttime (Chang et al, 2016; Hu et al, 2016; Lei et al, 2022; Yan et al, 2019). For example, in a subalpine forest, it has been reported that Rs was more sensitive to temperature change at night (Hu et al, 2016), while no significant difference of Q 10 was observed between daytime and nighttime in a beech forest (Janssens & Pilegaard, 2003).…”

Soil Respiration Response to Simulated Precipitation Change Depends on Ecosystem Type and Study Duration

“…We leveraged a pre‐existing soil respiration database (SRDB version 5, Jian et al., 2021) and filtered for studies that manipulated precipitation (increase, decrease, or both) and reported at least one of the following for both treatment and control field plots: (a) annual soil respiration, (b) mean growing season soil respiration, or (c) annual soil heterotrophic flux. Although the proportion of annual respiration that growing season respiration comprises varies by ecosystem (Brooks et al., 2005; Hu et al., 2016), the mechanisms underlying responses to precipitation change are the same. Additionally, despite heterotrophic measurements lacking plant root respiration, this flux often represents more than 50% of soil respiration (Jian et al., 2022).…”