The Local Biome of the Sonoran Desert

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The Local Biome of the Sonoran Desert
Module 2
Introduction In this exercise we attempted to
determine the area one has to sample before
adequately representing the community of plants
and arthropods in the local biome. This is
important in order to measure the biodiversity of
the local biome.
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Methods

• We conducted our study within a total plot area
  of 64 square meters within the Biosphere 2
  Campus, which is located in an area referred to
  by Tony Burgess as the Apacherian Scrub-Savanna
  habitat in the Arizona Upland region of the
  Sonoran desert biome. We started with a four
  square meter plot of sloping desert terrain and
  then doubled the area four times until we covered
  a total area of 64 square meters. This gave us a
  total of five plots. Thereby, we examined the
  rate of increase of plant species and arthropod
  morphotaxa with increasing plot size.
• To collect the arthropods we placed a beating
  sheet underneath plants and used an aluminum rod
  to expel the arthropods from the plants on to the
  sheet. We then proceeded to collect the
  arthropods in vials with aspirators. We also
  captured arthropods in vials with the use of our
  hands. We then used dichotomous keys and field
  reference books to identify the arthropods. To
  record the plant species we gathered branches and
  leaves from plant samples and also examined the
  intact plants on the ground. We used dichotomous
  keys to identify the cacti and field reference
  books to identify the other plants.
• Finally, we examined the data collected using
  Microsoft Excel spreadsheets and graphs.

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Methods (contd)
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Results of Plant Research

• The plotted area examined was found to contain
  a total of 14 different species of woody-stemmed
  plants and succulents, although one species of
  Cholla was not conclusively identified. The total
  plant species were graphed against the area
  examined to produce a species-area curve, and a
  logarithmic trend was created. The total species
  within the plot were compared to the 2000 data
  graphically.
• The results are as follows

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List of Collected Plant Morphotaxa in Sample Area

• Calliandra eriophylla
• Opuntia chlorotica
• Mammillaria microcarpa
• Salsola kali
• Eriogonum
• Fouquieria splendens
• Bebbia juncea
• Opunita engelmannii
• Casia covesii
• Acacia greggii
• Opuntia acanthocarpa
• Ambrosia
• Hibiscus denudatus
• Unknown small cholla

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Discussion Plant Biodiversity of Sample Area

• The data collected at the Biosphere 2 Center
  site during 2001 indicate a logarithmic
  relationship between plot area and the total
  number of plant species found within the plots.
  Within a 64 square meter area, a total of
  fourteen different plant species were recorded.
  In comparison, in the year 2000, 19 total species
  were identified within a 256 square meter plot.
  The data from the current year showed 8 species
  that were not found in the data last year, and a
  total of 13 species that were found in the
  previous year that were not found this year. The
  relationship between area and total number of
  plant species is consistent within the two sets
  of data despite significant differences in plot
  size.
• The collection and comparison of the two
  datasets within the Sonoran desert biome
  indicates a rich diversity of plant species
  despite the size of a small plot sampling. Even
  though the area examined in the previous year was
  much greater than the area sampled in 2001, there
  were species that were not present within the
  larger plot, but were identified within the
  smaller. This observation would reinforce the
  variability of a biome not necessarily being
  dependent upon the size of the area studied.

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Results of Arthropod Research

• In the four square meter plot, plot 1, we found
  seven arthropod morphotaxa. In the eight square
  meter plot we found two more unique arthropod
  morphotaxa. In the sixteen square foot plot we
  found eight more arthropod morphotaxa, in the 32
  square foot plot we found 12 more arthropod
  morphotaxa, and in the sixty-four square foot
  plot we found eight more morphotaxa. The total
  number of arthropod morphotaxa we found is 37.

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List of Collected Arthropod Morphotaxa

• white Hemiptera, black stripes on back with two
  orange stripes
• Very small green six legged with wings and two
  red dots
• Small black ant (order Hymenoptera family
  Formicidae)
• Larger light brown ant (order Hymenoptera family
  formicidae)
• Tan walking stick (order Orthoptera family
  Phasmatidae)
• Fly with glossy black abdomen (order Diptera)
• White moth 1cm (order Lepidoptera)
• Male Cicada Western or Apache orange coloration
  on wings (order Homoptera family Cicadidae)
• Reddish brown Homoptera with a black bottom
• Tiny red ant (order hymenoptera family fomicidae)
• A black and gray Orthoptera with tan stripes on
  hind legs
• Small Hemiptera with black bottom
• Flying black Termite (order Isoptera)
• Irridescent green fly
• Largest Hemipetra with yellow coloration near
  head and solid green back
• White Hemipetra, with darker more intense oragne
  and black
• Small Fly (order Diptera)
• Grayish white inch-worm
• White body black head spider (order Araneida)

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Discussion Arthropod Biodiversity of Sample Area

• In the 64 square meter area studied at the
  Sonoran Desert Biome in 2001, a total of 37
  arthropod morphotaxa were identified. The 2000
  SEE-U group covered a total area of 256 square
  meters and identified a total of five arthropod
  morphotaxa. The two studies were conducted at a
  similar site and time of day, but ten months
  apart. The 2001 SEE-U class found over seven
  times as many species in a significantly smaller
  area. One possible reason for this observation
  could be the fact that the 2000 SEE-U class did
  their in the beginning of August, and the 2001
  class did their research in the beginning of
  June. In the summer of 2000 the monsoon season
  came in the beginning of June, so that although
  the 2000 group had more recent periods of rain,
  both studies were done during dry periods. The
  time seperation from heavy rains could have
  affected the amount of arthropod morphotaxa
  found. Additionally, both groups could have
  erred in their identification of arthropod
  morphotaxa. Nonetheless, we feel that the main
  reason behind the discrepancy in the findings of
  total arthropod morphotaxa between the two years
  is effort level. Last summers group only had
  two individuals searching for arthropods and they
  did not search extensively through detritus.
  This summers group had four people searching for
  and identifying arthropods, and did extensive
  searching through detritus, and thereby, found
  many morphotaxa. This difference is most clearly
  seen upon examining the 32 square meter plots
  from each study. Last years team found 4
  morphotaxa, and in this plot this years team
  found 29.

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Conclusion to Module 2 Plant and Arthropod
Biodiversity for Sample Area in Sonoran Desert
Highlands Biome.

• How much area is necessary to adequately
  characterize a biome? In particular, in a
  diverse biome, like the Arizona Highlands of the
  Sonoran Desert, how much area must be sampled to
  accurately represent a biological community? It
  is a well-established principle of community
  ecology that the number of species discovered in
  a biome is directly proportional to the area
  sampled. The purpose of this study was to
  investigate this relationship. The crux of the
  matter is that as large as a sample area one may
  take, there will always be species that are not
  represented at what point (even on a graphic
  scale) does this relationship reach some kind of
  equilibrium and allow the researcher to
  categorize the biome?
• Over the course of this exercise, seven SEE-U
  students analyzed a 64 square meter area on a
  south-facing hillside in the Sonoran desert in
  the area of Biosphere 2. Using the methodology
  described above, we sampled 37 morphotaxa, and 14
  species of plants, plotting the result over the
  area examined.
• If one just considers this summers arthropod
  morphotaxa data, one cannot come to a meaningful
  conclusion as to what area one has to sample
  before adequately representing the community of
  plants and arthropods in the local biome. If one
  extrapolates our curve there is a relative
  leveling off point of the number of morphotaxa
  found per area at about 300 square meters, but,
  because many more morphotaxa were being found
  with each new plot, clearly, more work needs to
  be done.
• However, when one considers the plant species
  data gathered, one can observe a more conclusive
  relationship between the species found and the
  area sampled. Based upon the species composition
  of the smaller vs. larger area, it would appear
  that a larger area supports slightly higher
  number of species. But, this is not to conclude
  that a smaller area is less diverse, as there
  were several species represented within the
  smaller plot that were not identified within the
  larger area.

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References
Borror, Donald J. and Richard E. White.1970. A
Field Guide to Insects America North of Mexico.
Houghton Mifflin, Boston. Bowers, Janice Emily
and Brian Wignall. 1993. Shrubs and Trees of the
Southwest Deserts. Southwest Parks and Monuments
Association, Tuscon. Coronado RCD Area. Shrubs
of Southeastern Arizona. Coronado RCD Area,
Arizona. Elmore, Francis H. and Jeanne R.
Janish. 1976. Shrubs and Trees of the Southwest
Deserts. Southwest Parks and Monuments
Association, Tuscon. Fischer, Pierre C. 1989.
Seventy Common Cacti of the Southwest. Southwest
Parks and Monuments Association, Tuscon. Milne,
Lorus and Margery. National Audubon Society Field
Guide to North American Insects and Spiders.
1995. Alfred A. Knopf, New York. Nelson, Richard
and Sharon. 2000. Easy Field Guide to Common
Desert Cactus. Primer Publishers,
Phoenix. Phillips, Steven J. and Patricia
Wentworth Comus. 2000. A Natural History of the
Sonoran Desert. Arizona- Sonoran Desert Museum
Press, Tuscon. Robbins, Travis, David Lancaster,
Janna Lancaster and Dr. Tony Burgess. Biosphere 2
Center Plant Field Guide. Unpublished.
Biosphere 2 Center, Oracle, AZ. Sanders, Darryl
P. and Arwin V. Provonsha. A Pictorial Key to the
Orders of Adult Insects. Department of
Entomology, Purdue University. Lafayette, IN.