Data

An extensive survey was conducted to assess the species diversity of natural desert vegetation around the CAP-LTER study area. Remnant patch habitats (mostly parks and preserves) occurring within the urban matrix / fringe were emphasized. Three outlying areas (White Tank mountains west of town, Union Hills north of town, and Usery Mountain Park east of town) were surveyed for comparison.

Vegetation sampling

The original intent was to provide data on the woody and spring / summer herbaceous species in each area, but drought conditions allowed the spring herbs to be surveyed twice (1998, 2001) and summer herbs surveyed only once (1999). Thus, all locations have woody data but only a subset has herbaceous data. Surveys consisted of transects (elaborated below) summarized by the patch or outlying area name followed by a number (e.g. Unhill-11, Squaw-40, Hayden-8). Herb datasets are signified by a ‘P’ for spring and a ‘U’ for summer following the transect number (e.g. PaPk-1P, PaPk-1U).

Samples were stratified by habitat type defined geomorphologically: flatland; slopes facing N, S, E, and W; wash; and higher elevation analogs of these in South Mountain Park and Squaw Peak Recreation Area. Samples were organized as transects of circular quadrats measuring 100 m2 and separated by 20 meters from edge to edge (or 31.28 meters center to center). Woody species were recorded and counted within each quadrat. For transects with herbaceous sampling, the herb species present were noted. Herb samples also contain smaller 1 m2 square subquadrats within which the presence of woody and herb species were recorded. There were four subquads, each arranged along one of the four cardinal directions (NSEW). These subquads were situated parallel and to the right of a given directional line, with one side on the line starting two meters from the center of the larger circular quadrat. Transect location was chosen randomly. A nickel and penny were tossed in the air; when they landed, they formed an imaginary arrow with the nickel as its base and the penny indicating direction. Ten double paces (e.g. ten left foot steps) were taken in the indicated direction. The coins were tossed again. A rock was thrown in the indicated direction behind the head (blindly) and its landing position noted, where the first quadrat is to be placed. The coin toss is also used to indicate transect trajectory, unless available area is limited and remaining within a habitat is a problem. In that case, coins were flipped to choose from a set of compass trajectories (e.g. HEADS select 100 degrees over 90 degrees).

Permission for Access:

Authorization to conduct nondestructive field work, signed on February 17, 1998 and addressed to Charles Redman and Nancy Grimm, in Phoenix parklands.

Permission to survey a conservation area in North Mountain Park (“water catchment area near 7th Street” parking lot / trailhead) was obtained from the Park Manager.

Permission to sample areas on Camelback Mountain was obtained from the Park Manager. A lot of the mountain is privately owned, so straying too far from the summit trail was not acceptable. Echo Canyon Recreation Area was available for survey.

Access to State Trust lands in the Union Hills area was gained by contacting the Arizona State Land Department (www.land.state.az.us).

Access to the National Guard property in northern Papago Park was gained by contacting the superior officers staffing the facilities.