Soil carbon · Biodiversity
More plant species meant more soil carbon — through microbial biomass, not efficiency
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Short answer
Plant diversity raised soil organic carbon by 29%, and the path ran through microbial biomass and fungal necromass rather than through carbon-use efficiency.
What happened
Prommer and colleagues sampled the Jena Experiment in September 2015, measuring soil organic carbon, microbial biomass, growth, respiration, carbon-use efficiency, and fungal versus bacterial necromass, then linked the pools with path analysis. Microbial biomass rose 58% and growth roughly doubled from monocultures to 60-species plots, while respiration rose only 1.5-fold. Carbon-use efficiency showed no significant response. Soil carbon tracked microbial biomass more closely than root carbon.
Why it matters
The intuitive account of diversity and soil carbon is more plant input, more carbon stored. This points instead at microbial necromass — dead microbial bodies — as the accumulating pool, which is a different target for anyone modelling soil carbon under land-use change.
Evidence
- Study type
- Field survey of a long-running grassland biodiversity experiment with path analysis
- Sample
- 85 plots spanning 1–60 plant species in the Jena Experiment, sampled September 2015
- Journal
- Global Change Biology · peer reviewed
- Replication
- Not assessed in this corpus; the microbial-necromass account is supported by other systems but not tested here
- Limitations
- A single sampling date in one German grassland. Path analysis is correlational. The result does not establish that the same route operates in forests, croplands, or under warming.
What this connects to
Sources
The 2 studies this explanation is built from, by the role each plays. Every source links to PaperFren’s explanation of it and to the original paper.
Primary study
- Plant diversity builds soil carbon via microbes
Higher plant species richness raises soil organic carbon by boosting microbial growth, biomass, and fungal necromass, not carbon-use efficiency.
What it does not showLimitations
A single September 2015 snapshot in one German grassland cannot prove that the same microbial path operates in forests, croplands, or under future climate; CUE was statistically unchanged rather than shown to be irrelevant in all soils.
PaperFren explanationStudy with cards and a quizOriginal paper (DOI)cc by
Supporting evidence
- Shrubs and trees empty subarctic soil carbon
At a Swedish subarctic treeline, shrub and birch plots stored far less soil organic carbon than nearby heaths and respired that carbon faster, implying woody expansion can accelerate soil C loss.
What it does not showLimitations
Space-for-time cannot prove future shrub advance will lose the same carbon; moth defoliation likely understated forest ECM growth; root C was not fully inventoried; permafrost and waterlogged tundra may respond differently.
PaperFren explanationStudy with cards and a quizOriginal paper (DOI)cc by
Before
Soil carbon gains under higher plant diversity were commonly attributed to greater root carbon inputs, with microbial physiology treated as a pass-through.
Now
Microbial biomass and turnover explain more of the pattern than root input does in this grassland. One sampling date at one site, and carbon-use efficiency was statistically flat rather than shown to be irrelevant everywhere.