Effects of diurnal warming on soil respiration are not equal to the summed effects of day and night warming in a temperate steppe

Abstract

Abstract. The magnitude of daily minimum temperature increase is greater than that of daily maximum temperature increase under climate warming. This study was conducted to examine whether changes in soil respiration under diurnal warming are equal to the summed changes under day and night warming in a temperate steppe in northern China. A full factorial design with day and night warming was used in this study, including control, day (06:00 a.m.-06:00 p.m., local time) warming, night (06:00 p.m.-06:00 a.m.) warming, and diurnal warming. Day warming showed no effect on soil respiration, whereas night warming significantly increased soil respiration by 7.1% over the 3 growing seasons in 2006-2008. The insignificant effect of day warming on soil respiration could be attributable to the offset of the direct positive effects of increased temperature by the indirect negative effects via aggravating water limitation and suppressing ecosystem C assimilation. The positive effects of night warming on soil respiration were largely due to the stimulation of ecosystem C uptake and substrate supply via overcompensation of plant photosynthesis. Changes in both soil respiration (+20.7 g C m −2 y −1 ) and GEP (−2.8 g C m −2 y −1 ) under diurnal warming are smaller than their summed changes (+40.0 and +24.6 g C m −2 y −1 , respectively) under day and night warming. Our findings that the effects of diurnal warming on soil respiration and gross ecosystem productivity are not equal to the summed effects of day and night warming are critical for model simulation and projection of climatecarbon feedback.

Multifactor controls on terrestrial N<sub>2</sub>O flux over North America from 1979 through 2010

“…A large amount of field experiments still treat it as negligible, although a few experiments have introduced this in their experiment design (Xia et al, 2009;Reich et al, 2006). Through this study, the multi-factor interaction was recognized playing an important role in contributing to terrestrial N 2 O flux (Sect.…”

Day and night warming have different effect on root lifespan

“…The warming treatment commenced on 23 April 2006. The detailed description of warming treatment can be found in previous publications Xia et al, 2009). …”

“…Climate warming is expected to result in unequal changes in daily minimum and maximum temperatures, with the greater trends of night warming than day warming (Eastering et al, 1997;Alward et al, 1999;Zhou et al, 2007). It has been reported that increased daily minimum and maximum temperatures have different effects on biomass and yield (Dhakhwa et al, 1998;Alward et al, 1999;Peng et al, 2004;Lobell, 2007;Lobell and OrtizMonasterio, 2007) as well as C cycling Xia et al, 2009) in terrestrial ecosystems. However, it remains unclear whether asymmetrical warming may have different effects on root growth, mortality and turnover, which plays critical roles in regulating nutrient and C cycling between above-and belowground.…”

Q10 values vary with different kinetic properties of C mineralization

“…Thus, the kinetic parameters of various soil C pools should be fitted to the observational data to determine the temperature sensitivity of the C mineralization, including the rate constants and the relative sizes of the C pools of varying decomposability (Davidson and Janssens, 2006). Furthermore, the temperature sensitivity of C mineralization not only varies in those kinetic properties, which are partially determined by soil properties , but also changes with environmental conditions, such as constant vs. varying temperature regimes (Conant et al, 2008;Fang et al, 2005;Nakajima et al, 2016;Xia et al, 2009;Zhu and Cheng, 2011), the aeration statuses (Blagodatskaya et al, 2014;Devêvre and Horwáth, 2000;Diakova et al, 2016), the forest stands (Guo et al, 2016;Gutiérrez-Girón et al, 2015;Rey and Jarvis, 2006), and the soil horizons (Laganière et al, 2015;Xu et al, 2014). These constraints, especially the temperature and the aeration status, are fixed as constant in most studies, and a continuously changing vs. constant environmental comparison has rarely been scrutinized (Conant et al, 2008;Hartley et al, 2008;Pettersson and Bååth, 2003;Ranneklev and Bååth, 2001).…”