Forest Inventory and Analysis National Program

Program Features

Forest Health Indicators

Vegetation Indicator

The Vegetation Indicator is a set of variables collected on the Phase 3 (forest health) FIA plots. It is designed to assess the type, abundance, and spatial arrangement of all trees, shrubs, herbs, grasses, ferns, and fern allies (horsetails and club mosses) occurring on the plots.

Measuring vegetation allows us to report on the relative diversity of both native and introduced species. Information about the abundance and arrangement of species (structure) allows us to classify plots into community types. By remeasuring plots over time, we can monitor for change outside expected rates.

Why is the Vegetation Indicator Important?

Information about forest vegetation diversity and structure can be used to:

• Examine which forest types are most prone to invasion by non-native species.
  
  
• Determine which states, ecoregions, and forest types are most diverse or contain unique species.
  
  
• Assess tree diversity on a plot more thoroughly than P2 measurements allow. Among other things, this allows us to predict succession on a plot.
  
  
  

The Vegetation Indicator also provides data to classify plot vegetation into community types:

• Forest community types based on both overstory and understory plant species are highly correlated with ecosystem properties, such as productivity, response to disturbance, and use by wildlife.
  
  
• This may allow us to extrapolate other forest health indicator results to broader areas than the plots themselves, and with more accuracy than by forest cover type.
  

With remeasurement, we can:

• Assess trends over time in relation to other forest health indicators.
  
  
• Examine forest communities’ resistance to and resiliency following disturbance.
  
  
• Provide an early warning indicator of forest response to stresses like pollution, certain land uses, and disturbance events.
  

For more information about the Vegetation Indicator view the FIA Vegetation Indicator Fact Sheet.