Abstract
AbstractIdentifying the factors that control soil CO2 emissions will improve our ability to predict the magnitude of climate change–soil ecosystem feedbacks. Despite the integral role of invertebrates in belowground systems, they are excluded from climate change models. Soil invertebrates have consumptive and nonconsumptive effects on microbes, whose respiration accounts for nearly half of soil CO2 emissions. By altering the behavior and abundance of invertebrates that interact with microbes, invertebrate predators may have indirect effects on soil respiration. We examined the effects of a generalist arthropod predator on belowground respiration under different warming scenarios. Based on research suggesting invertebrates may mediate soil CO2 emission responses to warming, we predicted that predator presence would result in increased emissions by negatively affecting these invertebrates. We altered the presence of wolf spiders (Pardosa spp.) in mesocosms containing a forest floor community. To simulate warming, we placed mesocosms of each treatment in ten open‐top warming chambers ranging from 1.5° to 5.5°C above ambient at Harvard Forest, Massachusetts, USA. As expected, CO2 emissions increased under warming and we found an interactive effect of predator presence and warming, although the effect was not consistent through time. The interaction between predator presence and warming was the inverse of our predictions: Mesocosms with predators had lower respiration at higher levels of warming than those without predators. Carbon dioxide emissions were not significantly associated with microbial biomass. We did not find evidence of consumptive effects of predators on the invertebrate community, suggesting that predator presence mediates response of microbial respiration to warming through nonconsumptive means. In our system, we found a significant interaction between warming and predator presence that warrants further research into mechanism and generality of this pattern to other systems.
Highlights
Understanding what controls the rate of CO2 release from the soil is imperative
Microbial biomass was not predicted by warming, predator presence, their interaction, or any other variables collected in this study (Figure 5)
CO2 efflux did not increase under warming as it did in the absence of predators
Summary
Understanding what controls the rate of CO2 release from the soil is imperative. Soil carbon emissions account for 10x more CO2 release than anthropogenic inputs, and the potential for positive climate-soil carbon emission feedbacks makes identifying the mechanisms behind soil carbon emissions important (IPCC, 2013; Schlesinger & Andrews, 2000). Earth System Models (ESMs) used to predict climate change include only microbial and plant respiration in calculations of soil CO2 emissions (Wieder, Bonan, & Allison, 2013). This approach fails to take into account the complexity of soil food webs, which are comprised largely of invertebrates that control microbe and plant dynamics. Soil invertebrates can directly and indirectly alter soil microbe abundance and community structure. A. Wardle, 2006), which may be important in determining soil CO2 emissions (De Vries et al, 2013; Strickland, Lauber, Fierer, & Bradford, 2009). A. Wardle, 2006), which may be important in determining soil CO2 emissions (De Vries et al, 2013; Strickland, Lauber, Fierer, & Bradford, 2009). Strickland et al (2009) suggest that microbe community structure may explain up to 20% variation of total carbon respiration
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