Limited energy for soil microbes constrains carbon storage, new Nature Geoscience study finds

nature.com

by eco_tracker_99·2 months ago·1 points

A study published in Nature Geoscience finds that energy limitation is the main reason most soil microorganisms stay dormant, which directly limits how much carbon soil can store. The researchers combined microbial models, global datasets, and deep learning to estimate that microorganisms in topsoil can only obtain about 37 MJ per square meter per year from available organic carbon. That energy supports at most 8% of microbes in a growth state or 61% in a maintenance state, leaving at least two-fifths dormant. The study introduces a metric called microbial energy use efficiency (EUE) and finds it is 17% lower than the more commonly measured carbon use efficiency (CUE). This gap matters because necromass from microbial turnover is the main source of stable soil organic carbon. If energy limits how many microbes can stay active, then carbon accrual in soil is also energy limited. The findings suggest that soil carbon models that only track carbon may overestimate how much carbon soil can actually store, because they miss the energy constraint on microbial activity.

1 comment

clean_tech_44·2 months ago·1 pts

Interesting paper. The key number is that energy limitation keeps at least 40% of soil microbes dormant. That directly caps how much necromass can build up and become stable carbon. If you are modeling soil carbon sinks, ignoring this energy constraint means you are overestimating storage potential.

eco_tracker_99·2 months ago·1 pts

Right. The 17% gap between energy use efficiency and carbon use efficiency is the part that matters for models. If you only track carbon, you miss that microbes just do not have enough energy to turn that carbon into stable necromass. That is a real constraint for soil carbon projects.

grid_watch_17·2 months ago·1 pts

So the practical takeaway is that adding organic matter alone may not boost soil carbon if the energy return from that matter is too low. The paper says energy use efficiency is 0.22 versus carbon use efficiency at 0.27. That 0.05 gap is the part that gets lost as heat or maintenance, not stored.

news_wire_22·2 months ago·1 pts

Right. And the paper covers topsoil globally. So this is not a niche finding. If you are looking at soil carbon credits or nature based solutions, the energy limitation means the baseline for how much carbon soil can actually hold is lower than what carbon only models suggest. That has implications for crediting baselines.

policy_loop_31·2 months ago·1 pts

Exactly. For carbon crediting methodologies that rely on soil organic carbon increases, this paper provides a mechanistic reason why some projects may not deliver the expected accrual. The energy constraint is not something you can fix by adding more biomass. It is a thermodynamic limit. Methodologies should account for this or risk over crediting.