Ingrid M. Lubbers, Matty P. Berg, Gerlinde B. De Deyn, Wim H. van der Putten, Jan Willem van Groenigen
5 min
Soil fauna are known to influence greenhouse gas (GHG) emissions, but most research has focused on the effects of individual species. This study investigated how the diversity and functional composition of soil fauna—including earthworms, potworms, mites, and springtails—collectively influence the emission of carbon dioxide (CO2) and nitrous oxide (N2O) in managed soil.
The researchers used a microcosm experiment with hay-amended soil to test combinations of up to eight soil fauna species. By varying the species richness and functional dissimilarity of these communities, they measured the resulting GHG fluxes over 120 days. They also calculated net biodiversity effects to determine whether species interactions were facilitative or inhibitive compared to the expected sum of individual species' contributions.
The study revealed a clear trade-off in how soil fauna diversity affects GHG emissions. Higher species richness and functional dissimilarity led to a modest increase in CO2 emissions (up to 10%), likely due to more efficient litter decomposition. Conversely, these same diverse communities significantly suppressed N2O emissions (up to 62%). While earthworms acted as keystone species that generally increased emissions, the presence of a more diverse community of other soil fauna mitigated the N2O-promoting effects of earthworms. This suggests that a functionally diverse soil community promotes more complete denitrification, converting N2O into less harmful nitrogen gas.
These findings suggest that soil biodiversity is a critical, yet often overlooked, factor in climate regulation. In agricultural systems, where soil biodiversity is frequently degraded, restoring a diverse faunal community could serve as a natural strategy to mitigate N2O emissions—a potent greenhouse gas—without necessarily sacrificing the carbon cycling processes that drive soil health. The results provide a strong argument for agricultural management practices that prioritize the conservation of soil faunal diversity.
Soil faunal activity can be a major control of greenhouse gas (GHG) emissions from soil. Effects of single faunal species, genera or families have been investigated, but it is unknown how soil fauna diversity may influence emissions of both carbon dioxide (CO2, end product of decomposition of organic matter) and nitrous oxide (N2O, an intermediate product of N transformation processes, in particular denitrification). Here, we studied how CO2 and N2O emissions are affected by species and species mixtures of up to eight species of detritivorous/fungivorous soil fauna from four different taxonomic groups (earthworms, potworms, mites, springtails) using a microcosm set-up. We found that higher species richness and increased functional dissimilarity of species mixtures led to increased faunal-induced CO2 emission (up to 10%), but decreased N2O emission (up to 62%). Large ecosystem engineers such as earthworms were key drivers of both CO2 and N2O emissions. Interestingly, increased biodiversity of other soil fauna in the presence of earthworms decreased faunal-induced N2O emission despite enhanced C cycling. We conclude that higher soil fauna functional diversity enhanced the intensity of belowground processes, leading to more complete litter decomposition and increased CO2 emission, but concurrently also resulting in more complete denitrification and reduced N2O emission. Our results suggest that increased soil fauna species diversity has the potential to mitigate emissions of N2O from soil ecosystems. Given the loss of soil biodiversity in managed soils, our findings call for adoption of management practices that enhance soil biodiversity and stimulate a functionally diverse faunal community to reduce N2O emissions from managed soils.
Sam: That's a useful frame. So the diverse community doesn't shut down denitrification, it completes it.
Alex: Exactly. And there's a wrinkle worth flagging. CO2 emissions rose slightly in the more diverse treatments. That's actually mechanistically coherent — a more functionally diverse community is more efficient at decomposing organic matter, which drives higher respiration. But the global warming potential arithmetic still favors diversity heavily, because the nitrous oxide reduction dominates.
Sam: So it's a net win on radiative forcing, even if the carbon accounting looks slightly worse in isolation.
Alex: That's the authors' position, and the logic holds given the potency differential. The number that carries the paper's main claim is that 62% reduction in nitrous oxide flux — that's the load-bearing result. The CO2 finding is important context, but it's supporting evidence, not a countervailing finding.
Sam: Where does the inference break down?
Alex: The microcosm scale is the obvious constraint. A controlled lab environment gives you clean identification, but soil is spatially heterogeneous in ways that are essentially impossible to replicate at bench scale. Pore structure, moisture gradients, organic matter distribution — all of that varies across a real agricultural field in ways that could amplify or dampen the effect. The authors are appropriately cautious about this. The mechanistic story is credible, but whether the effect size survives translation to field conditions is genuinely unknown.
Sam: So the catalytic converter works in the lab. Whether it survives being installed in an actual field is the open question.
Alex: That's a fair characterization. And it points to what the obvious next step is — field-scale manipulations with realistic community reassembly, ideally across soil types and management regimes. The other thing a careful referee would push on is the assembly of the diverse communities themselves. Reintroducing mites and springtails to a tilled field isn't trivial — you need to know whether those communities can establish and persist, not just whether they function well once present.
Sam: So the paper establishes the mechanism and the direction of the effect. The translational questions are still open.
Alex: Which is actually a well-scoped contribution. They've given you a clean causal estimate under controlled conditions and a plausible mechanistic account. That's a solid foundation for the field work that needs to follow. The broader implication — that soil management practices which preserve or restore functional diversity might be a lever for agricultural emissions reduction — is worth taking seriously, even with the caveats.
Sam: It reframes the conversation a bit. Instead of just asking what we're putting into the soil, we should be asking what communities we're maintaining in it.
Alex: And that's a question that current agricultural policy frameworks aren't really set up to answer. Thanks for listening to ResearchPod.