Step 4: Supplemental Monitoring, Sample Sizes, and Frequency

Step 4: Select and document supplemental monitoring methods; estimate sample sizes; set sampling frequency; develop implementation rules
Step 4a: Select and document supplemental monitoring methods (if required)

  • Decide whether supplemental indicators are necessary to meet management and monitoring goals. Keep in mind that adding supplemental indicators will require additional work in the field and beyond (see below).  
  • If supplemental indicators are necessary to meet management goals and monitoring objectives, first evaluate the core and contingent methods to determine if these supplemental indicators can be calculated using a core or contingent method.
  • If a necessary indicator cannot be calculated from the core or contingent methods, select a supplemental method:
    • Select supplemental methods that are used by other monitoring programs and are documented clearly in a peer-reviewed method manual.
    • Other desirable characteristics of supplemental indicators and methods include: relevant to Land Health Standards; measurable objectively and consistently in many ecosystems by different observers; scalable; and applies to multiple objectives.
    • Be sure to document the rationale for including the supplemental indicator as well as a citation for the method. We strongly advise against creating new methods or modifying existing methods.
  • Additional tasks to complete in order to implement supplemental indicators include:
    • Practice the supplemental method in the field to establish how it will work with AIM plot layout and requirements (e.g., not walking on left side of a terrestrial transect)
    • Identify data management protocol and tools for the supplemental method, including: data recording, electronic data capture, data storage, quality assurance and control, and analysis and reporting.
    • Establish calibration standards for the supplemental method.
    • Identify capacity to provide technical support for the supplemental method (e.g., who will answer questions about it during the field season).
    • Plan sufficient training for successful implementation of the supplemental method. This cannot be during a core methods training, although we recommend that it follow soon after.
    • Consider the additional time required for a crew to complete the supplemental method at each sampling site to ensure that the cumulative impact of supplemental methods does not impair the crew’s ability to visit the desired number of sites in the landscape.
    • Using the process outlined in tables 1, 2 and 3, determine how data generated from supplemental methods will be used to inform management decisions

Step 4b: Estimate sample sizes

  • The number of monitoring sites needed for a monitoring design is a function of several factors: 1) the amount and quality of existing or legacy monitoring information, 2) the amount of resource that needs to be monitored, 3) statistical considerations, and 4) funding and personnel limitations.
  • If significant amounts of comparable, high quality monitoring data already exist, the required sample size may be smaller than when such data is not available. Make sure to inventory pre-existing monitoring data when you begin to plan your AIM monitoring efforts.
  • The number of points required in each stratum should balance the proportion of the resource that will be represented by the stratum with the weight of the points (see below for more information).
    • For more information about statistical considerations, see Step 5.
    • A terrestrial field crew with 3 people can monitor approximately 50 plots per season.
    • An aquatic field crew with 2-3 people can monitor 25-35 reaches per season.
  • The default method for allocating sample sizes is to proportionally allocate points based on the area/length that the stratum covers. For example, if you plan to sample 50 points in a season, and a particular strata covers 10% of your study area, you would sample 5 points.
  • The recommendation is to start with the proportional allocation approach and then adjust sample sizes up or down as needed. Frequently, the number of sample points will need to be increased in areas that cover a small percentage of the study area in order to achieve a sample size sufficient enough to provide information for management decisions. For example, black sagebrush areas often occupy a small portion of the landscape but provide important sage grouse habitat, and thus will need to be well represented in a design that is focused on sage grouse.
  • If you increase the desired number of points in one stratum, others may have to be reduced, to keep the total number of points sampled the same. Changing sample sizes will affect point weights (see below) in each stratum, and should be done with care.
  • Allocating zero points to any strata is not recommended because it will limit your ability to draw inference to the entire landscape, and should not be done unless: 1) the stratum is not part of the target population defined by your monitoring goals and objectives (e.g., open water in a terrestrial monitoring effort) or, 2) the stratum is being monitored as a part of a separate monitoring effort.
  • Point weights are the area (in acres or hectares) or length (in stream kilometers) represented by an individual sample point. Weights are used to generate statistical estimates of resource status or condition across the landscape (i.e. proportional estimates). Specifically, weights are used to adjust the relative influence that each point has on the final estimates; points with larger weights have more influence, and points with smaller weights have less. The weight of each point depends on the design and how it was implemented (see final designations) as well as the reporting area of interest.

Instructions for filling out the remainder of the Sample Design Table:

  • Proportional area or length: Divide the number of acres or stream km represented by each stratum by the total number of acres or stream kilometers in the entire study area to get proportional areas/lengths.
  • Proportional points per stratum: Calculate the proportional number of points per stratum by multiplying the proportional number of acres or stream km by the total number of points to be sampled.  
  • Final Points per stratum (optional): If a proportional allocation of points will not satisfy your monitoring objectives, adjust the number of points that will be monitored for each stratum. Calculate the number of sites you would like to sample in each stratum, taking the four factors mentioned above into account.  In the event that points are allocated in a way that is highly disproportionate to the proportion of the landscape that is represented by a given stratum, the proposed point allocations should be reviewed by someone at the NOC.
  • Point weights: Once all of the other columns in the Sample Design Table have been finalized, point weights can be calculated as the total number of acres or stream km within the stratum, divided by the number of points to be monitored for that stratum.  

Step 4c: Set sampling frequency

  • Most monitoring efforts need to be spread out across several years to accommodate field crew capacity and to insure that interannual variability is captured by the monitoring data. Once the total number of sample points and the point weights have been calculated, determine how many years of sampling might be necessary to achieve the desired sample size.  Factors to consider when setting sampling frequency include:
    • To reduce bias from year-to-year climate variability (e.g., drought), a rotating panel design (where a certain number of points, all contributing to the same design, are sampled over several years) is typically recommended. Rotating panels help ensure that sample points are randomly distributed across the entire project area every year.
      • For example, a 5 year design would consist of 5 panels, where each point is assigned a specific year panel in which it should be sampled.
      • In contrast, when specific geographic areas are sampled in only 1 or 2 years rather than during every year of the design, bias from climate variability can affect condition estimates.
    • Detecting change in condition through time (i.e., trend) is a common monitoring objective that requires setting an interval for revisiting points over time. Factors to consider when setting sampling frequency include:
      • What sampling frequency makes sense relative to the disturbance or management event? For example, ES&R monitoring dictates annual re-visits for three years, whereas monitoring stream geomorphic changes following livestock removal might occur on a 3-5 year basis, and changes in upland condition might occur over 5-10 years.
      • How resistant and/or sensitive to disturbance are the areas that you are monitoring? How resilient are those areas following disturbance events? You may want to consider establishing more frequent revisit intervals in areas that are more sensitive or less resilient to disturbance than in areas that are highly resistant and resilient.
      • What resources will be available (e.g., funding and personnel)?
      • What proportion of points need to be revisited to detect trend?
  • The default revisit interval for Resource Management Plan effectiveness monitoring is every 5 years for terrestrial systems and every 5 years for aquatic systems, unless natural conditions or management actions occur that would elicit landscape-scale responses on shorter time-scales.
  •  Depending on objectives, only a subset of points may need to be revisited. In general, trend assessments can be made by resampling approximately 30-50% of the original points (the actual percentage will vary by project).
  • Some monitoring efforts will not need to determine sampling frequencies on account of various project constraints or intentional design.

Step 4d: Develop implementation rules

  • Review standard AIM implementation rules, including rejection criteria, on aim.landscapetoolbox.org under Data Collection.
  • Proper design implementation involves documenting the fate of each point in a given design. Documentation of point fate should be tracked using the Terrestrial Plot Tracking Tool, and the Aquatic Design Management Spreadsheet. For more information and to download these tools and their instructions, visit the Point Evaluation and Rejection page.
  • If the implementation rules need to be customized to meet you monitoring objectives, consult with the NOC when developing the additional criteria to ensure the design will remain statistically valid.

Step 4 Example: Supplemental Monitoring, Sample Size, Monitoring Frequency, and Implementation Rules

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Step 4a: Select and document supplemental monitoring methods (if required)

Terrestrial – Supplemental methods – Terrestrial monitoring indicators and methods can be found in BLM Tech Note 440 and the Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems (MacKinnon et al. 2011; Herrick et al. 2015).  The core terrestrial indicators are sufficient for evaluating most of the terrestrial management and monitoring objectives, as discussed in Steps 1 and 2.  However, several supplemental indicators were identified that were not addressed by the core indicators:  sagebrush shape, distance to nearest sagebrush patch and distance to nearest juniper/tall structure.  These supplemental indicators inform sage grouse habitat questions as part of the Sage Grouse Habitat Assessment Framework (Stiver et al. 2015).  Distances to nearest sagebrush patch and distance to nearest juniper/tall structure can be measured using GIS with minimal additional field time, especially with the help of good notes taken by the field crew (Stiver et al. 2015).  The Field Office GIS staff will capture this information in an Excel spreadsheet following the field season.  A standard method for describing sagebrush shape, consistent with the HAF is available in the National Resource Inventory (NRI) protocol (National Resources Inventory 2016).  This information will be recorded every time a sagebrush plant is hit while doing Line Point Intercept, and electronically captured using DIMA.  Supplemental training for field crews and field office staff will be made available to ensure that these methods are implemented successfully.   

Aquatic – The aquatic core indicators will be sufficient for evaluating most of the aquatic management goals and monitoring objectives. However, the Utah Standards of Rangeland Health require that the BLM assess whether streams are meeting State water quality standards for e. coli. Since e. coli exceedances are only likely to occur in streams that are impacted by grazing, e. coli samples will only be collected at streams that are heavily used by cattle. E. coli samples will be submitted to the Utah Department of Environmental Quality, Division of Water Resources for analysis. The Aquatic Ecologist in the West Desert District will train the field crew on e. coli sample collection methods.

Step 4b: Estimate sample sizes

Terrestrial – Sample sizes were determined for each stratum based on field crew capacity and the final proportion of acres represented by each stratum (Sample Design Table).

Sample points per BpS unit will be proportional to BpS area on the landscape except where monitoring objectives suggest alteration (Figure 3; Sample Design Table; see Steps 4 and 5).  Within the broader District, a decision was made to intensify monitoring within sagebrush-dominated strata (mountain big sagebrush and Wyoming big sagebrush) to address sage grouse habitat management objectives. Sampling intensity was reduced in the Shadscale-Winterfat strata.

Aquatic –  To balance personnel capacity, statistical power, budget etc., we worked with NAMC/NOC to select a sample size of 50 stream reaches for the district. We anticipate that a sample size of 50 will allow us to estimate the proportion of stream km in a given condition category with 80% confidence. Supplemental points can be added to increase the precision and accuracy of estimates as needed.

There were no river km on BLM managed lands in the West Desert District, therefore we will only monitor small and large streams. Proportional allocation of points to small and large streams would have resulted in fewer than 10 points on large streams which seemed like an insufficient sample size, so we increased the point allocations in the large stream category to obtain a larger sample size and decreased the number of points allocated to small streams to keep the total number of sample points to the desired number of 50 points for the district.

Step 4c: Set sampling frequency

Terrestrial – One field crew can collect approximately 50 points in a monitoring season, so we intend to sample 100 plots per field season, for 5 years. Thus  we are planning to hire and run two three-person field crews to collect terrestrial monitoring data for each of the 5 years.

After the initial 5 year effort is complete. We plan to revisit 75% of terrestrial points on a five-year rotating basis in order to estimate trend.  

Aquatic – In our area, one aquatic field crew can collect data at approximately 25-30 reaches in a year. Thus to accomplish the desired sample size of 50 points, we plan to hire one, 2-person crew for the next two years.

The objectives for trend monitoring will be determined after baseline conditions are established. Specifically, follow up monitoring will be focused on any indicators that raise red flags. The temporal scale that we will use to implement subsequent monitoring will depend on which indicators need to be monitored and the temporal scale that we expect them to change in response to natural environmental variability and/or management actions. For example, recommendations might be to assess water quality indicators on a monthly basis if exceedances are observed. In contrast, bank stability would be assessed on an annual or semi-annual time-scale.   

Step 4d: Develop implementation rules

Terrestrial and Aquatic – We will use the standard AIM implementation rules, the Terrestrial Plot Tracking Tool, and the Aquatic Design Management Spreadsheet to implement the designs and to document the fate of all design points (see aim.landscapetoolbox.org).

Additional implementation rules are that the supplemental indicators will be collected at each terrestrial plot (see step 7).

 

Helpful Documents and Links

Monitoring Design Worksheet

Monitoring Design Worksheet Instructions

Monitoring Manual for Grassland, Shrubland, and Savanna Ecosystems

Shiny Tool for calculating sample size

Java applets for power and sample size

BLM Tech Note 440

Sage Grouse Habitat Assessment Framework

National Resources Inventory 2016 – Sagebrush shape protocol 

Terrestrial AIM_Data Management Protocol_V3.0

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