Sands/Choppy Sands (Sand bluestem-Little bluestem)
Page 1.
Introduction: discussion of classification, seral assignment and monitoring.
Page 2.
Graph.
Page 3.
Instructions: plot setup and data collection using the Excel spreadsheet.
Page 4.
References.
Caution
Sands.xls is an Excel workbook containing the datasheet for field data collection. Copy the Excel file to a PDA. The .xls
file will be converted to a Pocket Excel file with a .pxl extension. The file contains a spreadsheet with formulas that
provide calculations necessary for classification of a site, using the variables defined for this ecological type.
Be careful with the spreadsheet when loaded on a PDA. Although the formulas and cells are protected on the PC version
of Excel, protection of spreadsheets/worksheets is not an option on the Pocket version of Excel. It is possible to erase
formulas and stop the classification system. Be sure to make changes only within the empty cells, and not in any of the
calculation or formula cells such as cov%, probabilities, etc.
In addition, always:
•
Keep a backup copy of the original ‘Sands.pxl’ file on your PDA and,
•
Save the file under a new name after finishing data collection on each site, e.g. ‘Sands site1.pxl’, ‘Sands
site2.pxl’…….. to avoid overwriting previous files with data.
Monitoring Seral Stages in Sand bluestem-Little bluestem Ecological Type
Classification, seral assignment, and monitoring of sand bluestem-little bluestem ecological type seral
stages is according to the method of Uresk (1990). Statistical analysis of field-collected data indicates the
presence of four seral stages: early, early intermediate (EINT), late intermediate (LINT) and late. A site is
classified, and assigned to a seral stage by entering a set of key plant indices into the set of canonical
discriminant functions developed for this ecological type and estimating posterior probability for each seral
stage (SPSS, 1995). The site monitored is assigned to the stage with the highest posterior probability.
For the sand bluestem-little bluestem ecological type, the key species are Andropogon hallii (ANHA),
Bouteloua hirsuta (BOHI) and Schizachyrium scoparium (SCSC). Indices for these species are developed
from data collected using the Daubenmire (1959) canopy cover method. This method requires field collection
of canopy cover and frequency of occurrence for each of the three plant species. The index is produced by
multiplying total cover by frequency of occurrence (as a percent) for each species for the overall site.
The seral stage assigned to a set of plant indices is always associated with the greatest probability value. If
that value is 1, then succession is at the middle of the assigned seral stage. If the greatest probability value is
less than 1, then the second greatest probability value is used to determine the successional status relative to
middle of the assigned stage. For instance, if the second greatest probability is associated with an earlier seral
stage, succession is at the lower end of the assigned seral stage. On the other hand, if the second greatest
probability is associated with a later seral stage, succession is at the upper end of the assigned stage (see
example below).
When permanent macroplots are established to assess the vegetational trend of a site, re-sampling and
comparing the previously assigned seral stage to the current stage provides information about succession or
retrogression. On a finer scale, within-stage changes in vegetation successional status can be quantified by
comparing the probability values. For example, first-year field measurements collected for canopy cover and
frequency of occurrence on a site resulted in the following index values: ANHA=2200, BOHI=900, and
SCSC=1900. Four years later the index values obtained were: ANHA=2100, BOHI=600, and SCSC=2400.
Calculating the probabilities, we find:
ANHA BOHI SCSC
LATE LINT
EINT
EARLY
Stage
Year1
2200
900
1900
.000
.961
.039
.000
LINT
Year5
2100
600
2400
.000
.593
.407
.000
LINT
Difference
In both years, the site was classified and
assigned to the late intermediate seral stage; the
greatest probability values (.961 in Year1 and
.593 in Year5) are associated with LINT.
Placement within the late intermediate seral
stage is at the lower end of the stage, as
indicated by the second greatest probability
values (.039 for Year1 and .407 for Year5)
which are associated with an earlier seral stage
(EINT).
The site shows a downward
successional change of about .37, which is the
difference between the probabilities in Year1
and Year5.
The figure to the right illustrates this
example. These quantitative changes in the
probabilities can be used to evaluate and
monitor the effects of management alternatives.
.368
Late
Late Intermediate
.96
Early Intermediate
Early
Year 1
1.0
.5
Late
1.0
.5
1.0
1.0
.5
Late Intermediate Early Intermediate
.59
Early
Year 5
1.0
.5
Late
1.0
.5
1.0
Early Intermediate
Late Intermediate
.37
1.0
.5
Early
Change
1.0
.5
1.0
.5
1.0
.5
1.0
Page 1 of 4
Monitoring Seral Stages in Sand bluestem-Little bluestem Ecological Type
Sand bluestem-Little bluestem
Ecological Type by Seral Stages
3500
3000
Hairy grama
Sand bluestem
Little bluestem
Index values
2500
2000
1500
1000
500
0
LATE
L.INTERMEDIATE E. INTERMEDIATE
EARLY
Mean Index
Hairy grama
Sand bluestem
Little bluestem
2,184
507
955
327
2698
1,031
146
278
3,121
101
470
215
Mean indices of plant species through four seral stages of succession in a sand bluestem, little
bluestem ecological type. Smoothed lines connect the means for each key plant species at each stage.
Graph provides a guide for an approximate mixture of species at each seral stage.
Page 2 of 4
Monitoring Seral Stages in Sand bluestem-Little bluestem Ecological Type
DATA COLLECTION, SUMMARIZATION AND CALCULATIONS
1. Establish two parallel 30 m permanent
transects 20 m apart as a plot within the sand
bluestem-little bluestem ecological type.
Recommendations are to establish two plots
per section within the ecological type.
2. Using the ‘Sands.xls’ spreadsheet (see figure
at left) installed on your PDA, record canopy
cover within a 20cm x 50cm quadrat for
Andropogon hallii (ANHA), Bouteloua
hirsuta (BOHI) and Schizachyrium
scoparium (SCSC) at one-meter intervals
along each transect (30 readings/transect)
using Daubenmire (1959) classes 1 through
6.
Class Code
1
2
3
4
5
6
Cover Class
>0 - 5%
5 - 25%
25 - 50%
50 - 75%
75 - 95%
95 – 100%
Mid Point
2.5%
15%
37.5%
62.5%
85%
97.5%
The spreadsheet calculates percent canopy cover,
frequency-of-occurrence, and index values for each
plant species for each transect and for the site. It also
provides the classification probabilities by seral
stage and the seral stage assignment.
Sands.xls
Calculations
Cover (%) = Sum Daubenmire midpoint values for each
species per transect, divide by 30. Site cover = mean
cover of the 2 transects.
Frequency (%) = Divide the number of plot frames in
which the species is present by the total number of plot
frames on the transect. Convert that value to a percent by
multiplying by 100. Site frequency = mean of the 2
transects.
Index = the Site Cover mean times the Site Frequency
mean. ((Xsect 1 cover + Xsect 2 cover) / 2) x ((Xsect 1
freq + Xsect 2 freq) / 2)
Page 3 of 4
Monitoring Seral Stages in Sand bluestem-Little bluestem Ecological Type
REFERENCES
Daubenmire, R. 1959. A canopy-coverage method of vegetational analysis. Northwest Science.
33(1):43-64.
SPSS 12.0 for Windows. 1989-2003. SPSS Inc. 444 N Michigan, Ave, Chicago, IL 60611.
Uresk, D. W. 1990. Using multivariate techniques to quantitatively estimate ecological stages in a
mixed grass prairie. J. Range Mgt. 43(4):282-285.
Page 4 of 4