Abstract
Abstract. Both long-term observation data and model simulations suggest an increasing chance of serious drought in the dry season and extreme flood in the wet season in southern China, yet little is known about how changes in precipitation pattern will affect soil respiration in the region. We conducted a field experiment to study the responses of soil respiration to precipitation manipulations – precipitation exclusion to mimic drought, double precipitation to simulate flood, and ambient precipitation as control (abbr. EP, DP and AP, respectively) – in three subtropical forests in southern China. The three forest sites include Masson pine forest (PF), coniferous and broad-leaved mixed forest (MF) and monsoon evergreen broad-leaved forest (BF). Our observations showed that altered precipitation strongly influenced soil respiration, not only through the well-known direct effects of soil moisture on plant and microbial activities, but also by modification of both moisture and temperature sensitivity of soil respiration. In the dry season, soil respiration and its temperature sensitivity, as well as fine root and soil microbial biomass, showed rising trends with precipitation increases in the three forest sites. Contrarily, the moisture sensitivity of soil respiration decreased with precipitation increases. In the wet season, different treatments showed different effects in three forest sites. The EP treatment decreased fine root biomass, soil microbial biomass, soil respiration and its temperature sensitivity, but enhanced soil moisture sensitivity in all three forest sites. The DP treatment significantly increased soil respiration, fine root and soil microbial biomass in the PF only, and no significant change was found for the soil temperature sensitivity. However, the DP treatment in the MF and BF reduced soil temperature sensitivity significantly in the wet season. Our results indicated that soil respiration would decrease in the three subtropical forests if soil moisture continues to decrease in the future. More rainfall in the wet season could have limited effect on the response of soil respiration to the rising of temperature in the BF and MF.
Highlights
Solid EarthAs one of the largest carbon fluxes in terrestrial ecosystems, soil respiration has received renewed attention in recent decades due to the concerns over its potential feedbetacakl.,to20fu0t0u;reBoclnidm-aLTtaemhcbehearnCtygeray(nTodrsuTmphbohomerepr,seo1n9,972;01V0a)l.enIttinisi generally accepted that rising temperature would accelerate CO2 release from soils, which in return reinforces anthropogenic warming (Cox et al, 2000; Luo, 2007)
Soils moisture in the broadleaf forest (BF) and mixed forest (MF) was relatively high in the wet season, so that root respiration and microbial decomposition may not be subject to water limitation. In these two forest sites, we found that the fine root and soil microbial biomass under the double precipitation (DP) treatment increased significantly in the dry season, but not in the wet season (Fig. 4)
We found that the DP treatments in the BF and MF reduced temperature sensitivities in the wet season (Tables 4 and 5)
Summary
As one of the largest carbon fluxes in terrestrial ecosystems, soil respiration has received renewed attention in recent decades due to the concerns over its potential feedbetacakl.,to20fu0t0u;reBoclnidm-aLTtaemhcbehearnCtygeray(nTodrsuTmphbohomerepr,seo1n9,972;01V0a)l.enIttinisi generally accepted that rising temperature would accelerate CO2 release from soils, which in return reinforces anthropogenic warming (Cox et al, 2000; Luo, 2007). Both climate models and satellite observations suggested change in precipitation patterns in the warm climate (Easterling et al, 2000; IPCC, 2007; Allan and Soden, 2008). Precipitation manipulation experiments showed variable effects on soil respiration in different ecosystems (Borken et al, 2006; Zhou et al,. 2006; Sotta et al, 2007; Davidson et al, 2008; van Straaten et al, 2010, 2011; Cleveland et al, 2010; Talmon et al, 2011), and extensive research is necessary to make an accurate assessment of its global impacts
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