Field Work

In order to quantify the camelthorn abundance, a belt transect method will be employed to generate coarse scale measurements of the entire field site. Each belt transect will be 50 m long and 4 meters wide. Start points for each transect will be determined randomly using a grid method measuring across the entire field site and then using a random number generator to pick points along the grid of where to start the transects. If a randomly generated start point is at least with in 5 meters of a previous transect, the new transect will be moved over 5 meters. The target number of transect will be 8, with possibly more given time and ease of collecting.
Figure 1. Site wide map and proposed design for transects. Transects locations will be determined by a random number generator.
The transects will be used to measure camel thorn abundance in three potential habitat types: Fremont, Open and Tamarisk dominated. Fremont habitat will only be recorded where there is a Fremont Cottonwood with in the transect, which is likely to be the most infrequent type of habitat. Open habitat will consist of 70 % open area with grass (Fig 2) while Tamarisk dominated will consist of 60% or more Tamarisk cover (Fig 3).
Fig 2. Open habitat type
Fig 3. Tam dominated

In each transect, habitat type will be quantified by discerning the area of open verses tamarisk dominated polygons (Fig 4). Camel thorn abundance will be recorded in each of the habitat polygons and then averaged across transects to infer a camel thorn density measure in the different habitat types.

Figure 4: Transect sampling method. Each habitat type will be measured along the transect and the area recorded. In each habitat polygon, camel thorn abundance will be counted.

In addition to camel thorn abundance, # of live or new stems will be quantified as a measure of plant vigor. Number of Tamarisk stems per Tam-dominated polygon will also be recorded.

Because Fremonts are very infrequent on the landscape, a targeted sampling scheme will be used in order to quantify camelthorn/ Fremont interactions. Three quadrants at 2 different distances (total 6 per tree) will be placed in random orientation around the base of the tree, and then at drip line. In each quadrant camel thorn abundance will be measured at two distances: near and dripline (Figure 5)

Fig 5. Sampling scheme for Fremont cottonwoods in order to quantify Fremont and Camelthorn interactions.

-Need to add Grass component

These different field sampling methods will help to answer the following questions:
  • How much of each habitat type is there on the landscape and what is the density of open space vs Tamarisk dominated?
  • Does camel thorn abundance/ density depend up on habitat type?
  • Does camelthorn vigor differ between habitat types?