Tuesday, September 30, 2014

Managing Drought Risk on the Ranch

Photo-Point Transect

Repeat photography is a quick and objective way to assess the cumulative effects of management and environmental variables on rangeland health. A couple of good pictures usually convey a message more effectively than volumes of numerical data.

This practice is easy, fast, repeatable, and one of the strongest chronological comparison records available to on-the-ground landscape managers.

Once the photo-points are established, field work for the entire ranch can be completed in several days in each subsequent year. 
 

Site Selection

Permanent photo locations are most helpful when placed in areas that are likely to be affected by changes in management. For example, locations at intermediate distances from livestock water are most likely to be affected when changing from season-long continuous grazing to a 4 or 5-pasture deferred-rotation grazing plan. These photo-points should be located on grazable range sites that are relatively common in the management unit or pasture.

Select monitoring locations on the basis of the desired information.

  • If you want to evaluate an entire pasture, choose a location on the range site that composes the majority of the grazable area in the management unit. These areas are called key areas
  • Additionally, unique sites with exceptional resource values or unusual susceptibility to damage may be monitored. These sites are called critical areas.

Place the entire transect on the appropriate range (ecological) site in an area that is likely to be affected by grazing, less than 1 mile from water. Avoid livestock and game trails, erosional features, fences, roads, and areas within 300 yards of livestock water. It is also important to avoid depressions or down-slope positions where additional surface flow of precipitation may occur. Changes on properly located key areas indicate similar changes have likely occurred over much of the pasture.


Equipment

  • Site Information and Photo-Point Transect Forms.
  • Two 6-foot carpenter rulers, two steel rebar transect stakes, 100-foot tape, graduated staff.
  • Digital Camera and Photo Information Sheet.
  • GPS unit, compass
  • Green T-bar steel reference posts
  • 1-gallon zip-lock freezer bags

Photographs should always include an object that can be used to scale the image. Plot frames or graduated staves with known dimensions are widely used to scale photographs. Always include a graduated staff and the skyline in panorama photos for scaling and relocation.


Do:

  • Take photographs before grazing and during early morning or late afternoon, to provide the best contrast in shades and colors.
  • Include the photo information sheet inside the frame of every picture for that site.
  • Take pictures during the same stage of plant growth each time.
  • Include the same skyline in repeat landscape pictures.
  • Carefully relocate the photo-points each time.
  • Maintain consistency in camera type and settings and associated  documentation.

Don't:

  • Take photographs near near solar noon, 11 a.m. to 2 p.m., when visual contrasts are minimal.

Interpretation

When comparing photographs for a specific photo-point over time, look for:

  • Changes in the vigor, cover, or density of plants.
  • Changes in the amount of visible bare ground.
  • Evidence of erosion.

Corresponding Field Notes

Corresponding field notes should include the dominant 3 to 4 native species of grasses, forbs, and shrubs listed from most to least dominant on the basis of weight. Relative abundance of invasive or undesirable species should also be recorded (wide spread, intermediate, or limited).

Grazing, precipitation, and brush management records are needed to determine the most probable cause of changes. Additionally, photo transects on similar range sites in nearby winter pastures or non-grazed areas can provide valuable information on vegetation responses to environmental variables in the absence of summer grazing. Installing a transect in a nearby similar pasture where management is unchanged is helpful when evaluating new management.

Procedure for Establishing Transect
and Taking Photos

 example site information form

Establish a 100-foot transect with a permanent stake at each end. 

Complete Photo Information Sheet for the site. Use flat yellow or blue paper to reduce exposure problems in the photograph. Use a wide-tipped black marker to write on the sheet.

Include the sheet in each photo so that a record of when and where the photo was taken is included in each photo.

example of 100-foot transect with site information form

From behind the stake at the start of the transect, take a landscape photograph looking down the transect towards a relocatable bearing point.

Photopoint frame

Using the two carpenters rulers, create a 3x3 foot square frame and lay it over the tape so it intersects it at the 5-foot and 8-foot marks. Standing over the tape, take a photograph looking down at the framed section with the 5-foot mark in the foreground and 8-foot mark in the background.

Photopoint along transect

Repeat the previous process (using the frame) at the 50-foot to 53-foot marks and the 92-foot to 95-foot marks.

example of 100-foot transect with site information form

At the 100-foot end of the transect, take a photograph looking back down the transect to the 0-foot mark. A complete transect will include a total of 5 photos. Images:  Pat Reece

The National Drought Mitigation Center | 3310 Holdrege Street | P.O. Box 830988 | Lincoln, NE 68583–0988
phone: (402) 472–6707 | fax: (402) 472–2946 | Email Us

University of Nebraska-Lincoln
Copyright 2014 National Drought Mitigation Center