Vascular Plant and Vertebrate Inventory of Saguaro ... - USGS

Percent
120
100
80
60
40
20
0
Plant
Rock or Bare ground
Desertscrub
Oak Savannah
Pine-oak Woodland
terrain. Due to the fact that much of the district
remains unsurveyed, it is possible that we and
others have not reached the goal of documenting
90% of the plant species for the entire district.
However, if we look at inventory effort in
different areas, the completion estimates are
mixed. For example, low-elevation, more easily
accessed areas almost certainly have a species
list that is close to completion. We found only
three new species at or near focal points in the
low-elevation stratum, and only one new species
in an area near the Loop Drive, a highly visited
area. The park’s monitoring efforts have had
similar results in low-elevation areas; in their 25
long-term monitoring plots (surveyed for seven
years) park staff have found only 15 new species
for the district (Appendix A). The flora for the
high-elevation areas of the district is similarly
complete. We found only one species in the area
around Manning Camp, an area that has had
extensive plot-level research related to the fireeffects
program. That program has produced
only 30 new species in 15 years of surveys of 71
plots (Saguaro National Park, unpubl. data). By
contrast, the mid-elevation areas are the least
surveyed and our results reflect this; we found
most of our new species at focal points in the
middle-elevation stratum (e.g., plots 101 and 189
had four and three new species for the district,
22
Conifer Forest
Figure 3.6. Percent (mean + SD) ground cover from point-intercept transects by community type,
Saguaro National Park, Rincon Mountain District, 2001.
respectively). These plots were among the most
difficult to reach areas of the district (Fig. 3.3).
Based on this evidence, we suggest that the floras
for low- and high-elevation areas are nearly
complete and that future surveys should focus on
middle-elevation areas, especially the east slope
of the Rincon Mountains and the northeastern
boundary of the district.
Efficacy of Focal Points
Our plot and point-intercept work was insufficient
to describe all of the vegetation communities of
the district. Given the size of the district, the
random location of 17 study sites was certain
to miss a number of important features and
areas. These included communities such as the
semi-desert grasslands and riparian deciduous
woodland, and many areas such as the east
and northeast slopes of the Rincon Mountains
(Fig. 3.3). However, the plots and transects
were instrumental in (1) establishing long-term
monitoring plots, (2) getting researchers to areas
that had never been visited and therefore led to
the discovery of new species to the district’s flora,
and (3) providing information used in assessing
habitat associations for vertebrates.