Population Monitoring

A population is a group of individuals of the same species that have the ability to genetically interact and inhabit a defined geographic area.

Population monitoring involves consistent and repeated observations to detect, measure, assess, evaluate, and draw conclusions as to how species and ecosystems are changing through time and space.

Monitoring is a key component of rare plant conservation, required under several federal acts, for endangered, threatened, and rare species. Monitoring is also a key component of the adaptive management process where by demographic data inform management practices.

Flowering stems of the Schweinitz's sunflower (Helianthus schweinitzii)

Qualitative Data Metrics

Qualitative data monitoring can provide rapid assessments of species populations.

Presence or Absence: Documenting weather or not the species is still found on site.
Population size estimation: Counting a sample and sometimes a full census of the population (counting reproductive or large individuals).
Population condition estimation: Documenting observations such as signs of herbivory, disease, percentage in different life cycle stages, etc.
Vigor indicators: Plant height, number of flowers, number of leaves, diameter of rosettes, etc.

FoPC Staff counting flowering stems of Schweinitz's sunflower (Helianthus schweinitzii)

Demographic Monitoring

Assessment of detailed changes in population throughout the lifecycle; measures germination and mortality rates, growth, size, density, and distribution.

Population Viability Analysis (PVA): Mapping individual plants and marking all stages of the plant life cycle to construct a model for future population viability assessment. These analyses also allow forecasting time until extinction and modeling impact of management efforts.
Single age/stage class investigation: Measuring a few stages of the lifecycle such as seedling survival or longevity of adults.
Demographic structure: A measurement taken at one time to assess the distribution of individuals in age or stage classes (seedlings, juveniles, non-reproductive adults, reproductive, and old/dying).

Schweinitz's sunflower (Helianthus schweinitzii)

Habitat and Protected Area Monitoring

Detection or measurement of changes in focus habitat through repeated observations and recordings of the specific ecosystem from a previous status.

Best done with a standardized and repeated protocol.
Metrics should be quantitative where possible.
Document issues or problems needing attention (example: invasive species encroachment).

For more detailed information on methods for population monitoring check out this technical reference.

What to Bring into the Field

Clipboard
Standardized guidelines and recording sheets
Pencil
Rite in the Rain notebook or paper
Hand lens
Plant ID reference
Ruler and measuring tape
Compass

Yearly monitoring of Heller's blazing-star, Liatris helleri involves counting rosettes, height, and number of flowering stems.

Sources and Resources

Chapter 13: Monitoring of Areas and Species/Populations to Assess Effectiveness of Conservation/Management Actions

Elzinga, L. Caryl; Salzer, W. Daniel; Willoughy, W. John. Measuring & Monitoring Plant Populations. BLM Technical Reference 1730-1.

Vitt, Pati; Tienes, Melissa; Skogen, Kriss; Havens, Kayri. Optimal Monitoring of Rare Plant Populations II: Data Collection and Analysis. USDA Forest Service.