Does root respiration of subtropical Chinese fir seedlings acclimate to seasonal temperature variation or experimental soil warming?

Substrate and adenylate limit subtropical tree fine‐root respiration under soil warming

“…Currently, most studies on fine‐root respiratory thermal acclimation have been conducted in growth chambers or greenhouses (Bryla et al, 2001; Di Iorio et al, 2016; Noh et al, 2020; Rachmilevitch et al, 2008), and data from in situ field warming experiments are extremely limited (Jarvi & Burton, 2018, 2020). These previous studies have indicated that the effects of increased temperature on root respiration vary, with acclimation (Bryla et al, 2001; Di Iorio et al, 2016), partial acclimation (Chen et al, 2021; Jarvi & Burton, 2020), and little or even no acclimation being common (Melillo et al, 2011; Noh et al, 2020). This may be partly related to differences in the population structure of the fine roots sampled, sampling season, and climatic zones among these studies.…”

“…However, previous studies on root respiratory acclimation at the tissue and cellular level or ecosystem level often failed to control for the effects of differences in their population's fine‐root structure (Atkin et al, 2009; Jarvi & Burton, 2020; Noh et al, 2020). Second, the season sampling is conducted will affect the observation of fine‐root respiration acclimation in response to experimental warming (Chen et al, 2021). This has rarely been considered in previous studies (Jarvi & Burton, 2020; Wang et al, 2022).…”

“…This has rarely been considered in previous studies (Jarvi & Burton, 2020; Wang et al, 2022). Finally, owing to relatively narrow seasonal temperature ranges, tree species from tropical and subtropical areas may have lower capacities or higher temperature thresholds for thermal acclimation than those from cooler climates (Bryla et al, 2001; Chen et al, 2021; Cunningham & Read, 2003; Janzen, 1967; Krause et al, 2013; Slot & Kitagima, 2015). Despite this, studies on respiratory thermal acclimation of fine roots have primarily focused on temperate and northern ecosystems (Di Iorio et al, 2016; Jarvi & Burton, 2020; Vogel et al, 2014) and studies of tropical and subtropical forests have been lacking.…”

“…Since there might be a temperature threshold for respiratory thermal acclimation to occur (Bryla et al, 2001) and such temperature thresholds might be higher in subtropical forests than in cooler climates (Chen et al, 2021), our first hypothesis was that fine‐root respiration of subtropical Chinese fir acclimated to soil warming only during the summer when soil temperature is high, with SRR 20 lower under warming than under the control. Soil N availability is relatively higher in subtropical areas compared with high‐latitude areas, and warming will stimulate soil N mineralisation and further enhance soil N availability (Bai et al, 2013; Rustad et al, 2001).…”

“…Therefore, fine‐root respiration of Chinese fir may not be restricted by enzyme capacity. In subtropic areas, the basal root respiration rates are much higher due to higher ambient soil temperatures (Chen et al, 2021; Jarvi & Burton, 2020), and a similar temperature increase would likely cause a larger magnitude increase in root respiration rates than in high‐latitude areas. In other words, warming will exacerbate the respiratory C demand of subtropical trees, which might more easily lead to depletion of root carbohydrate storage and thus substrate restriction on root respiration, especially when higher temperatures and water stress may negatively affect plant photosynthesis and block the belowground transport of photosynthates (Arndal et al, 2018; Atkin et al, 2000; Fuchslueger et al, 2014).…”