Saturday, January 29, 2011

Old research...

I was looking for old papers that I had written that might contain the information I need for my proposal. I have done research in the Kiger HMA in the past and hoped I could use some of it to write up my “Study Area” section form my thesis proposal on Riddle Mountain’s HMA. While I did not find what I hoped, I did find the paper I wrote to go with the poster I presented at the 2008 Symposium Of University Research and Expression (SOURCE). It was declared an outstanding award and I got a gift card and a certificate. Good times. (I hope to do another one this year :o) Anyway, took me back….still need to find info on Riddle Mountain. I wish I could get grazing history from the BLM site.

Identifying Wild Horse Impacts Using Aerial Photography
Horses have been here in the Americas before, during the Pleistocene. However, somewhere between 10,000 and 14,000 years ago, they disappeared. Why is not entirely known, although it was most likely a combination of changing climate and overhunting by humans. When Spanish explorers brought their horses with them during the 16th century, horses again returned to the Americas after having been absent for thousands of years. This time, they thrived. The grasses were lush and the predators few, and now humans viewed them as transportation instead of food. By the 19th century, their population had peaked to an estimated 2-7 million. Horses competed for space on the range and conflicted with the livestock industry (Garrott et al 1991). As a result, horses were herded over cliffs, their water holes were poisoned, and they were shot. Some were corralled and left to die. Their population began to decline until there were about 9,500 in 1971. This inhumane treatment of the free-roaming horses brought about the 1971 Wild Free-Roaming Wild Horse and Burro Act. This act required these wild horses to be protected from harassment, branding, capture, or death, managed, and controlled on public lands. Further, as declared by congress, the act viewed them as living symbols of the historic and pioneering spirit of the West. Since their protection, their numbers have once again been on the rise, at as much as 20% of a population increase annually. This has implications for the health of rangelands in the United States. Aerial photography can be used as an agent in managing wild horses and determining rangeland health.

Large-scale aerial photography is a technique used to make inventory and monitor rangeland vegetation (Knapp et al., 1990). It began in the 1960s and large-scale came to be general use a decade later. With a larger scale, plants were able to be identified, percent cover could be estimated by photo analysis, one year intervals could keep track of the vegetation, and soil characteristics could monitored as well (Knapp et al., 1990). Over the years, bare ground can be used as a key indicator that a closer inspection of the area is required to assess the rangeland vegetation (Booth et al., UNK). Using dot-grids overlaid onto the photographs is a way to measure these changes of vegetation and bare ground (Knapp et al., 1990).

Common platforms for rangeland photography range from ultra lights (Booth et al., UNK), fixed wing aircrafts, such as Cessnas (Werth and Work, 1992), and helicopters. However, though helicopters can fly and hover at slower speeds, they are not a stable enough platform for a large format camera. Further, they are more expensive than a fixed wing aircraft.

Based on the work of Werth and Work (1992) the recommended scale for rangeland monitoring was 1:1000 to 1:1500 because it provided a photograph where categories of vegetation from trees to grasses can be identified. Also, these scales reduce the cost (Werth and Work, 1992). Another study using aerial photography for rangeland management examined the use of 1:200. However, they suggested further study of this scale because previously, scales of 1:600 were affected by motion blur (Booth et al., UNK).

Film types were generally color or color-infrared. One study stated that true color was preferred because it had a better resolution, reduced risk of improper exposure, and allowed more natural vegetation to appear than color infrared film (Werth and Work, 1992).

The air photos I used to examine the use of aerial photography in identifying wild horse impacts on rangelands were taken in southeastern Oregon. They are DOQs of Poison Springs in Harney County, Oregon, in which the exclusive Kiger Herd Management Area (HMA) is located based on information I obtained from the BLM office in the Burns District. The first image I examined was taken September 21, 1988. The second was listed as only the year 2005, so I could not be sure what time of the year it was taken, but based on the levels of vegetation, I guessed late spring, early summer.

Once I had these images, I used the ESRI program ArcMap to zoom in on the exclusive horse use area I was informed of to see impacts of these broad hoofed creatures. I found many horse transects leading to and from water and along ridges, where horses like to keep an eye out for predators. Grazing areas were characterized by lighter colors indicating less vegetation. I was also able to view these images in a remote sensing program, ERDAS Imagine, where I played with the contrast in order to view areas of more or less vegetation and water.

As a result of my study, I found that aerial photography could be used to identify wild horse impacts in areas of horse use. Further, monitoring these impacts can also be used by implementing repeat photography of these areas in order to examine impacts over time. As for my study, though I was able to distinguish the horse impacts clearly, such as more bare ground and trodden trails. I think I would have been able to see differences (such as more or less use) had these images been of a larger scale, as suggested in other rangeland management studies. Further, because these photos were taken at different times of the day, (the photograph from 1988 had more shadowed canyons on the east facing side, indicating they were taken later in the afternoon), I might have been able to make more notes of difference based on vegetation. 



1 comment:

  1. Yeah. Can't seem much with those photos on here. In the program ERDAS, I could really zoom in enough to see horse trails and water tanks even.