Productive Capacity Criteria and Indicators for Rangeland Ecosystems

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Productive Capacity Criteria and Indicators for
Rangeland Ecosystems

• Gary R. Evans
• R. Dennis Child
• 4 February 2003
• SRM Meeting in Casper, WY

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Basic Assumption

• Sustainability implies that
• Rangeland will provide goods and services for the
  current and future generations.
• Future generations can obtain their desired mix.
• The mix of goods and services desired by society
  at any particular time will be diverse.

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Our Approach

• The team focused on consumptive uses (traditional
  and non-traditional).
• Some standard ecological indicators like net
  primary productivity were included.
• Recognized that non-consumptive uses influence an
  ecosystems productive capacity and included some
  to understand potential trends.

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Our Approach

• Recognized that some uses are mutually exclusive
  Others are compatible to some degree.
• When examining the mix of goods and services
  found on rangeland that there is seldom a simple
  linear exchange ratio. (i.e. mixed species
  grazing.)

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Scale

• Multi-scale measurements are required. Data
  must be gathered within specified contexts and
  over both large temporal and spatial scales.
• Bailey Ecoregions could define the broadest
  scale.
• Major Land Resource Areas (MLRA) and Ecological
  Site Descriptions (ESD) to correlate existing
  survey data.

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Questions Considered

• What products, goods, and services are being
  produced that can be monitored?
• What products, goods, and services will be
  desired by future generations?
• How can issues of fragility and resiliency be
  considered?
• Should natural processes be monitored to account
  for change in productive capacity?
• Is it important to assess societal costs/benefits

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Maintenance of Productive Capacity

• Indicators selected
• Above Ground Biomass
• Rangeland Annual Productivity
• Percent Available Rangeland that is Grazed
• Number of Livestock on Rangeland
• Presence and Density of Wildlife
• Annual Removal of Commercially Harvested Biomass

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Indicator 1 - Above ground biomass.

• Annual above ground biomass is a direct measure
  of biomass production available to potential
  grazers of rangelands. It is a state variable
  measured in terms of mass/unit area.
• Importance Most of the traditional data
  available have been collected in terms of the
  annual growth increment of herbaceous and shrub
  species of interest on rangelands. These data
  sets provide invaluable data on the trends in
  above ground biomass production and form the core
  subsets of data for indicator 2.
• In some ecosystems, like temperate grasslands,
  annual above ground biomass are still the best
  available data, and will evolve toward measures
  of NPP in the future.

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Indicator 1 - Continued.

• Geographic Variation Rangeland vegetation types
  are highly variable in annual biomass production
  because of variation in precipitation,
  temperature and soil fertility. Annual sampling
  is needed to account for these short and
  long-term climate patterns and discriminatory
  analysis is needed to separate them from
  management impacts.

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Indicator 1 - Continued

• Scale Both ecoregion scales and the ecologic
  site description scale are useful in monitoring
  rangeland productive capacity.
• Data Data collecting, reporting methods and
  reporting procedures exist at national and
  regional levels. However, data collection
  methods are not standardized at either scale.
  Above ground biomass is collected in a variety of
  ways including
• Destructive above ground biomass sampling
• Weight estimate and regression procedures
• Clarity This indicator readily translates to
  map or GIS graphic forms for informing broad
  audiences.

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Indicator 2 Rangeland Annual Productivity .

• Rangeland Annual Productivity is measured as net
  primary productivity (NPP) and is the rate at
  which energy is converted to biomass within an
  ecosystem. It is a flow or ecosystem process
  measure in terms of g/unit area/time. NPP
  includes both above and below ground biomass.
  ANPP is the ecosystem measure of the amount of
  above ground biomass produced over time.

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Indicator 2 Continued.

• Importance Primary productivity is the
  foundation for measuring the productivity
  capacity of terrestrial ecosystems, and is key to
  understanding ecosystem sustainability.
• Sunlight is the engine that drives all
  productivity through the process of converting
  light energy and CO2 to energy in the form of
  sugars. These carbon compounds provide the food
  base far all secondary production in ecosystems.
  Changes in productivity affect the kind, amount,
  and distribution of life.
• Geographic Variation Annual above ground
  biomass and net primary productivity vary widely
  by vegetation type, which varies widely by
  region.

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Indicator 2 - Continued

• Scale Rangeland productivity is highly
  variable spatially and temporally. The
  indicators are meaningful when sample sizes are
  large enough to provide the necessary statistical
  power to detect change. Further interpretation
  can be enhanced through an understanding of
  climate and land use changes.
• Data NPP is measured in 4 primary ways.
• The direct, destructive sampling of above and
  below ground biomass.
• Root/shoot coefficients
• CO2 flux at the atmosphere/vegetation interface.
• Modeling

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Indicator 3 - Percent Available Rangeland that
is Grazed

• Provides information on land use patterns that
  may shift production from one commodity to
  another.
• Importance Used with other indicators to
  characterize the primary production consumed by
  livestock. It is an indicator of the net area
  used to produce livestock forage to the total
  rangeland within the ecoregion and the nation.
• Geographic variation Gives consistent
  information across geographic regions.

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Indicator 3 - Continued

• Scale Meaningful at different scales and will
  likely become a measure that is aggregated from
  management records at the management unit to the
  ecoregion.
• Data Conceptually feasible or initially
  promising, but no regional-national methods,
  procedures or data sets currently exist.
  Requires two pieces of data not uniformly
  available.
• The amount of rangeland at ecoregion scales that
  could be grazed and
• The determination that these lands are actually
  grazed.
• This information could be sensitive with many
  landowners and managers and will require careful
  definition.

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Indicator 4 - Number of livestock on rangeland.

• A direct measure of the secondary production
  based on rangeland.
• Importance Domestic livestock found on
  rangelands include cattle, sheep, goats, horses
  and mules, along with a number of minor grazing
  animals like llamas and alpacas. The long-term
  trends in numbers of cattle and sheep that spend
  at least part of the year on rangeland will be
  used.
• Geographic Variation The number of livestock
  grazing on rangelands is equally meaningful in
  all geographic regions.

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Indicator 4 - Continued

• Scale The indicator is meaningful from the
  individual operation to the national level.
• Data The number of cattle may be determined at
  a scale necessary for regional and national
  assessments. It is assumed that appropriate
  questions can be incorporated into surveys used
  by USDA-NASS. The proportion of the time spent
  on rangeland is not currently determined.

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Indicator 5 - Presence and density of wildlife.

• The presence and density of functional groups of
  wildlife provide an additional direct measure of
  secondary production based on rangeland.
• Importance Enables the use of indicator species
  that characterize secondary productive capacity.
  A complete inventory of major wildlife species is
  not feasible. Initial thoughts on functional
  groups include 1) large herbivores, 2) small
  herbivores, 3) large predators, 4) small
  predators, 5) avian foragers, 6) avian predators,
  7) burrowing reptiles, 8) surface reptiles, 10)
  fresh water fish, 11) pollinators, and 12)
  amphibians.

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Indicator 5 - Continued

• Geographic Variation Meaningful, but only by
  ecoregion.
• Scale Meaningful primarily at the broader
  scales between ecoregions and MLRAs
• Data Conceptually feasible or initially
  promising, but no regional-national methods,
  procedures or data sets currently exits.
• Clarity this indicator is potentially
  understandable to broad audiences. People tend to
  care about individual species welfare.

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Indicator 6 - Annual Removal of Commercially
Harvested Biomass.

• A highly diverse, yet important, array of
  products are taken on an annual basis from
  rangeland including
• landscaping and decorative plant materials
• edible and medicinal plants
• wood products
• native hay and
• native plant seeds.

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Indicator 6 - Continued.

• Importance
• Relatively high local value but may not be
  important nationally.
• Productive capacity can be altered by changing
  regeneration capacity of some species.
• Removal may change biodiversity and alter habitat
  in some sites.
• The impact of the removal of plant material is
  difficult to evaluate. For example, little is
  known about the impact of harvesting seed
  extensively in one location to be planted in
  another location.
• Government policies and public perceptions
  encouraging native species may increase demand.

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Indicator 6 - Continued

• Geographic Variation Ecoregion sampling designs
  will be needed that reflect the unique cultural
  and biological differences and the temporal
  product demand shifts.
• Data Availability Some data sets exist at the
  region-national level, but methods and procedures
  are not standardized at the regional-national
  level. Most of the currently available data is
  associated with site specific biodiversity
  issues, such as removal and depletion of
  landscaping cacti, high value cedar removal, and
  non-sustainable demands for medicinal herbs.
• On federal and state lands where harvesting
  activities are permitted there is a higher
  likelihood of monitoring the type and amount of
  material harvested. Private lands are subject to
  industry analysis of product availability. This
  is complicated by the fact that some products
  like mesquite are sold nationally while others
  like cactus for landscaping are sold locally.

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• Questions?