## Problem 193 — rank:170

**Title:** Soil biodiversity and ecosystem function

**Added binding assumptions (LaTeX):**

```latex
Write the biomass-controlled effect as $\tau_j(b)$ to distinguish intervention setting $B=b$ from conditioning on an endogenous post-removal biomass. Define feasible versions of the joint diversity/biomass intervention and any direct protocol effects. A decomposition into biomass-mediated and remaining effects needs additional causal assumptions and is not obtained merely by subtracting two marginal contrasts.
```

**Direct edits:** 1. **Fresh external checks:** None; supplied sources retained as provenance.