{
  "$schema": "https://terraevidence.com/evidence-record.schema.json",
  "recordId": "EP-PUB-010",
  "version": "1.0",
  "status": {
    "code": "reviewed-for-stated-scope",
    "label": "Reviewed for stated scope",
    "meaning": "Checked for the stated wording, sources, methods, context, limits, and review period; not universally proven."
  },
  "topic": "Forecast validation",
  "title": "A leading indicator is not a forecast until its prediction is validated.",
  "claim": "Plant water potential, stomatal conductance, and other early physiological measurements can provide biologically meaningful evidence about current plant state, but they should not be presented as forecasts of a later outcome unless prediction is evaluated for a defined outcome, time horizon, decision, population, and context of use.",
  "summary": "An early signal can be mechanistically relevant and associated with later performance without having demonstrated forecast accuracy. Predictive use requires prespecified outcomes and horizons, compatible measurement conditions, calibration and error assessment, and independent validation in the species, environments, and decisions where the forecast will be used.",
  "evidenceSupports": [
    "Define the future outcome, forecast horizon, decision, and acceptable error before calling a measurement predictive. Preserve species or cultivar, developmental stage, soil and root-zone conditions, light, temperature, vapor-pressure deficit, time of day, measurement method, baseline, and treatment context. Evaluate calibration, discrimination, false alarms, missed events, and performance on independent data from the intended setting."
  ],
  "doesNotEstablish": [
    "One low water-potential reading, one reduction in stomatal conductance, a mechanistic relationship, or a correlation with later performance does not by itself establish a portable forecast of yield, survival, recovery, resilience, or garden performance. A model that fits one dataset may still fail at a new site, season, cultivar, stress pattern, or forecast horizon."
  ],
  "sources": [
    {
      "sourceId": "EP-PUB-010-S1",
      "sourceType": "primary-study",
      "institution": "United States Department of Agriculture Forest Service",
      "title": "Plant water potential improves prediction of empirical stomatal models",
      "url": "https://research.fs.usda.gov/treesearch/63109",
      "relevance": "Reports a global analysis of 34 woody species in which adding sensitivity to declining plant water potential improved stomatal-conductance prediction during dry conditions while revealing diversity in stomatal strategies."
    },
    {
      "sourceId": "EP-PUB-010-S2",
      "sourceType": "peer-reviewed-review",
      "institution": "Journal of Experimental Botany",
      "title": "Irrigation scheduling: advantages and pitfalls of plant-based methods",
      "url": "https://academic.oup.com/jxb/article/55/407/2427/496045",
      "relevance": "Reviews plant water status and stomatal conductance as sensitive indicators while documenting physiological, environmental, measurement, and interpretation limits that affect their use in irrigation decisions."
    },
    {
      "sourceId": "EP-PUB-010-S3",
      "sourceType": "primary-study",
      "institution": "United States Department of Agriculture Forest Service",
      "title": "Growth and physiological responses of isohydric and anisohydric poplars to drought",
      "url": "https://research.fs.usda.gov/treesearch/50513",
      "relevance": "Compares contrasting poplar genotypes and shows differences in water potential, stomatal conductance, photosynthesis, growth, and recovery under drought, supporting the need to preserve species strategy and conditions."
    }
  ],
  "scope": {
    "reviewedPeriod": "2026-08",
    "applicability": [
      "Evaluating claims that plant water potential, stomatal conductance, soil moisture, or another early soil or plant signal predicts a later agricultural, ecological, or garden outcome."
    ],
    "limitations": [
      "Does not validate a particular sensor, threshold, model, crop, cultivar, irrigation schedule, or forecast horizon.",
      "The cited evidence establishes biological relevance and context dependence, not universal predictive performance across gardens, herbaceous crops, climates, or management systems.",
      "Does not provide personalized watering, irrigation, fertilizer, lime, amendment, crop, environmental, pest-control, or safety recommendations."
    ],
    "openQuestion": "Which combinations of plant water potential, stomatal conductance, soil moisture, weather, and plant observations predict defined garden outcomes early enough to improve a decision, and with what out-of-sample error rates?"
  },
  "useBoundary": "This reviewed record supports evaluation of candidate leading indicators and forecasts. It does not validate a particular measurement, sensor, threshold, irrigation rule, model, crop response, or garden recommendation; establish future yield, survival, recovery, resilience, or performance from one early signal; or provide personalized watering, irrigation, fertilizer, lime, amendment, crop, environmental, pest-control, or safety recommendations. Preserve the measured state separately from the predicted outcome and require fit-for-purpose, out-of-sample validation before using a forecast for a consequential decision.",
  "humanReadableUrl": "https://terraevidence.com/earth-project-reviewed-foundations#ep-pub-010",
  "machineReadableUrl": "https://terraevidence.com/evidence-records/ep-pub-010.json",
  "revision": {
    "version": "1.0",
    "publishedDate": "2026-08-17",
    "lastReviewedPeriod": "2026-08"
  }
}