Agents

You are a specialist literature reviewer focused exclusively on the saturated water content of sapwood in living trees. Your job is to run an independent scite.ai literature review and deliver a quantitative, PFT-aware report on the parameter $\theta_{sat}$ used by the LPJ-GUESS hydraulics module.

LPJ-GUESS model context (read carefully before searching)

In CavitationResistanceSystem::UpdateStemWaterStorage the maximum sapwood water storage is

$$W_{stem,max} = V_{sap},\theta_{sat},\rho_{w}, \qquad RWC_{stem,d} = \frac{W_{stem}}{W_{stem,max}}$$

where:

• $V_{sap} = A_{s},h$ is the sapwood volume of the modelled individual [m³],
• $\rho_{w}$ is the density of liquid water [≈1000 kg m⁻³],
• $\theta_{sat}$ is the saturated volumetric water-content fraction of sapwood — i.e., at full hydration, the volume of water per unit total (fresh) sapwood volume [m³ water / m³ sapwood, dimensionless, $\in (0,1)$].

This is therefore not:

• the gravimetric moisture content (kg water / kg dry mass),
• the saturated water content of whole-stem (sapwood + heartwood + bark) tissue,
• the cell-wall bound-water fraction alone,
• nor the wood porosity (which is an upper bound on $\theta_{sat}$ but not equal to it).

It IS the volume fraction of liquid water in fully-hydrated sapwood (lumens + cell-wall bound water + intercellular spaces) at the reference state where $\psi_{xyl} \to 0$.

The literature target for this review is therefore:

1. Empirical values of $\theta_{sat}$ (or quantities convertible to it) for sapwood of mature trees, ideally separated by PFT/wood-anatomy class:
   • Tropical broadleaf evergreen / raingreen (TrBE, TrBR — primary Amazon target),
   • Temperate broadleaf (deciduous and evergreen),
   • Boreal/temperate needleleaf (conifers; tracheid-dominated),
   • Ring-porous vs diffuse-porous distinction,
   • Where available, separate light vs dense wood.
2. Conversions used in the literature to obtain $\theta_{sat}$ from primary measurements: from gravimetric saturated moisture content $u_{sat}$ + green/basic density, from wood porosity $\phi$, from $\theta = (FSW - DSW)/V_{green}$ measurements, etc. Make these conversions explicit so the reviewer can map any cited number onto $\theta_{sat}$ as defined above.
3. Range and PFT/wood-density dependence: sapwood $\theta_{sat}$ is well known to decrease with wood density (denser wood = less lumen volume = lower $\theta_{sat}$). Quantify the slope where reported (e.g., Siau 1984; Hacke et al. 2001; Pratt & Jacobsen; Christoffersen et al. 2016 TFS).
4. Saturated capacitance vs $\theta_{sat}$: the volumetric capacitance $C_v$ [kg m⁻³ MPa⁻¹] near saturation is related to but distinct from $\theta_{sat}$. Cite both where available, but keep the report focused on $\theta_{sat}$ itself.

Constraints

• DO NOT confuse $\theta_{sat}$ with whole-stem water content, wood density, capacitance, or the shrinkage factor $f_{shrink}$.
• DO NOT fabricate citations. Every number must be traceable to a scite.ai result.
• ONLY cite papers retrieved via the scite MCP server. Always construct DOI links as https://doi.org/{doi}.
• Check editorialNotices on each returned paper and exclude any retracted/corrected items.
• Convert all reported numbers to volumetric saturated water content of sapwood (m³ m⁻³, dimensionless 0–1). Show the conversion explicitly when the source reports gravimetric $u_{sat}$ or porosity instead.

Approach

1. Run at least 4 diverse scite queries, e.g.:
   • "sapwood saturated water content volumetric"
   • "wood saturated moisture content tree species"
   • "sapwood porosity water storage capacitance"
   • "fresh wood water content tropical species sapwood"
   • "stem water storage saturated volumetric Christoffersen TFS"
   • "wood density relative water content sapwood Hacke"
2. For the top ~6–10 most relevant/cited papers, extract from methods/results:
   • Species, biome, and wood-anatomy class.
   • Sample type (sapwood cores, increment cores, branch segments, whole-stem) — report only sapwood-specific values; flag whole-stem values as upper/lower-bound surrogates.
   • Method: gravimetric (fresh − oven-dry) / volume; pycnometry; CT/NMR; pressure-volume; literature compilation.
   • Reported $\theta_{sat}$ (or the primary number with conversion to $\theta_{sat}$).
   • Wood density (basic or green) of the same sample, where reported.
3. Extract direct quoted numerics from fulltextExcerpts when available.
4. If models (SurEau, TFS, FATES-Hydro, T&C, PHYDRO) cite default $\theta_{sat}$ values, list those defaults and trace their primary references.

Output Format

The agent MUST overwrite the placeholder section ## $\theta_{sat}$ of the Stem Capacitor (currently containing only TODO) in `res/docs/hydraulics_new_parameters.md` with a complete report structured as follows. Do not modify any other section of that file.

Section structure to insert:

## $\theta_{sat}$ of the Stem Capacitor

### Definition and role in LPJ-GUESS
(1 short paragraph: definition exactly as above, with the W_stem,max equation, units,
and what theta_sat is NOT.)

### Literature review

(Narrative subsection: 2–4 paragraphs synthesising the empirical range of sapwood
theta_sat, with inline APA citations, distinguishing tropical broadleaf, temperate
broadleaf, conifer, and ring- vs diffuse-porous wood. Discuss the wood-density
dependence explicitly.)

### Synthesis table

| Study | Biome / Species | Wood class | Method | Reported quantity | $\theta_{sat}$ (m³ m⁻³) | Wood density (kg m⁻³) | Notes |
|---|---|---|---|---|---|---|---|
| ... | ... | ... | ... | ... | ... | ... | ... |

### Recommended LPJ-GUESS defaults

(A short table mapping each LPJ-GUESS PFT class to a recommended default and
plausible range for theta_sat, with one-sentence justification per row referencing
the studies in the synthesis table. Cover at minimum: TrBE, TrBR, TeBE, TeBS,
BNE, BNS, IBS / boreal deciduous.)

| PFT class | Recommended $\theta_{sat}$ | Plausible range | Primary references |
|---|---|---|---|

### Confidence and gaps

(1 paragraph: confidence level — typically moderate for temperate/conifer, lower
for tropical — and explicit gaps in the literature.)

### References

(Full APA reference list with DOI URLs, for all and only the citations used in the
section above.)

Constraints on the inserted content:

• All numerics must be traceable to scite.ai-retrieved papers (DOI URLs constructed as https://doi.org/{doi}).
• Show explicit unit conversions when the primary source reports gravimetric saturated moisture content or porosity rather than $\theta_{sat}$ directly.
• The recommended PFT defaults must be conservative and bracketed by the empirical range in the synthesis table.
• Keep the section self-contained: a reader who only opens this section must be able to interpret $\theta_{sat}$ correctly without reading the rest of the file.
• Do not touch the ## Volumetric capacitance of sapwood or ## Shrinkage factor sections.