Abstract
Assessing the response of soil heterotrophic and autotrophic respiration to climate change is critical for forecasting terrestrial carbon cycle behavior in the future. In the present study, we conducted a drought experiment in Vitexnegundo var. heterophylla shrub ecosystem of the Middle Taihang Mountain. Three precipitation manipulation treatments (natural conditions/ambient precipitation (CK), reduced precipitation by 30% (PE30), and reduced precipitation by 60% (PE60)) were used to study the impact of different levels of precipitation exclusion on total soil respiration (Rs) and its heterotrophic (Rh) and autotrophic (Ra) components. Our results showed that the rates of Rs and its components were significantly decreased under the precipitation exclusion treatments. The proportion of Rh in Rs reduced from 72.6% for CK to 71.9% under PE60. The annual cumulative C fluxes of Rs decreased by 47.8 g C m−2 in PE30 and 106.0 g C m−2 in PE60, respectively. An exponential relationship was observed between the rate of each soil respiration component and soil temperature in all treatments ( p < 0.01). Moreover, each soil respiration component rate was better represented by a quadratic model which included soil moisture ( p < 0.01). However, including both of soil temperature and soil moisture did not explain more variation in soil respiration components compared than the regression model with soil moisture only. In addition, excluding precipitation increased the temperature sensitivity (Q10 values) of Rs and its Ra and Rh components compared to the control. Collectively, our findings suggest that increased drought will inhibit the release of carbon from the soil to the atmosphere, and will likely decrease the contribution of Rh to Rs in this semiarid shrubland ecosystem.
Highlights
In future climate scenarios, the intensity and frequency of precipitation is forecasted to decrease in many areas (IPCC, 2013; Sun et al, 2019)
Based on a randomized block design, three replicate treatments were used to create precipitation gradients, including natural conditions/ ambient precipitation (CK), reduced precipitation by 30% (PE30), and reduced precipitation by 60% (PE60)
The present study provided unique data for exploring the impacts of precipitation exclusion on Rs and its components in a semiarid mountain shrubland of northern China
Summary
The intensity and frequency of precipitation is forecasted to decrease in many areas (IPCC, 2013; Sun et al, 2019). Precipitation reduction was reported to suppress Rs in arid and semiarid ecosystems (Talmon et al, 2011) but enhance it in tropical rainforests (Cleveland et al, 2010; Zhang et al, 2015) These contradictory results have been attributed to differences in vegetation types, climatic conditions, and soil microbial activities (Li et al, 2020; Liu et al, 2016). Rs is comprised of autotrophic respiration (Ra), produced by the activities of vegetation roots and associated organisms, and heterotrophic respiration (Rh), associated with decomposition of soil organic matter (SOM) through soil biota (Luo and Zhou, 2006) These two components represent different biological and ecological processes and respond differently to changes in environmental factors including soil temperature (Ts) and soil moisture (Ms) (Liu et al, 2016). Very few studies have combined manipulating precipitation with partitioning Rs into its component fluxes in semiarid shrublands
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