Maintaining monitoring design integrity while collecting field monitoring data is critical to retaining statistical rigor. Thus, AIM project leads and field crews should ensure that they are following the proper procedures throughout the field season to guarantee that designs are implemented correctly.
AIM uses probabilistic monitoring designs to randomly select monitoring locations (i.e. points) in a manner that evenly distributes points across the landscape. Probabilistic designs are used to select sample points from within the larger target population you seek to learn about (or make inference to). In landscape monitoring, the target population is the resource that you seek to report on within a defined study area. The use of probabilistic monitoring design enables us to make statistically valid inferences about the entire target population because every point in the study area has a chance of being sampled.
When a design is implemented, there are three possible outcomes for each sample point that is randomly selected within the study area. The first possible outcome is that data are collected at the sample point and those data will contribute to inferences about the target population. The second possibility is that the sample point is found to be outside of the target population (e.g., not on BLM land) and the point is removed from the design, thus not detracting from the statistical validity of the monitoring design. The third possible outcome, is that data are not collected at the sample point for a particular reason (e.g. due to safety, inaccessibility, etc.) but the sample point is still part of the target population. This last outcome will have a negative effect on the statistical rigor of the monitoring design, because it creates a “hole” in the sample frame.
Best Practices for Implementing a Monitoring Design
- Visit sample points in the assigned order wherever possible. This preserves the randomness of your design. If this is not possible, contact the NOC/NAMC for instructions on how to optimize logistics and still preserve the random sample. Click here to see illustrated examples of a properly and improperly implemented design.
- Make detailed notes regarding the status (i.e. sampled, rejected) and designation (i.e. target, non-target) for all points that were evaluated in the office or in the field.
- Maintain the exact plot names or stream reach site codes assigned to each point in the monitoring design – this is critical component of data management.
- Ask for help from the NOC/NAMC when you have questions about implementing the design.
Sample Point Evaluation
AIM sample points should be evaluated in advance of the field season to determine how the crew will navigate to and sample the point. Points should also be evaluated to determine if they meet any of the rejection criteria. This work is critical for field crew success in sampling points!
Point evaluation includes but is not limited to: looking over topographic maps and aerial imagery, getting site information from other field office personnel, going to the site in person, and/or contacting private landowners to obtain access permissions and instructions. Any information obtained during the point evaluation process should be recorded and stored in a consistent fashion so that the information can be accessed for trip planning and taken into the field.
If the person who did the point evaluation is not going into the field, the crew should be given the opportunity to review the information obtained during this process and ask questions prior to departing for the field.
More details on this process can be found on the Point Evaluation and Rejection Page and in the Aquatic Scouting and Sample Design Management Guidance document.
Trip Planning Steps:
Once the initial evaluation of sample points is complete and information about each point has been gathered, field trip (i.e. hitch) planning can begin. The individual responsible for planning hitches should pay close attention to properly implementing the monitoring design.
- With the set of office accepted sample points, take some time to think about how you might be able to visit groups of points efficiently, while paying attention to where each point falls within the monitoring design.
- Once you have a group of sites to potentially sample during the hitch, examine all of the scouting notes to determine what might be required of the crew to access the sites.
- If necessary, contact BLM staff or private landowners responsible for overseeing access to obtain access permission, gate keys or combinations, and access instructions.
- Obtain maps of all the areas slated for sampling. If you are unfamiliar with the area yourself, ask around the office for information regarding current road conditions, places to camp and get water, etc.
- Print all necessary information and upload digital copies onto the tablet.
Helpful Documents and Link