Nebraska Sedge
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
Nebraska Sedge.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 ‘Nebraska Sedge.pxl’ file on your PDA and,
•
Save the file under a new name after finishing data collection on each site, e.g. ‘Nebraska Sedge site1.pxl’,
‘Nebraska Sedge site2.pxl’,….. to avoid overwriting previous files with data.
Monitoring Seral Stages in Nebraska sedge-Baltic rush Ecological Type
Classification, seral assignment, and monitoring of Nebraska sedge-Baltic rush ecological type seral stages
is according to the method of Uresk (1990). Statistical analysis of field-collected data indicates the presence
of three seral stages: early, intermediate (INT), 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, 1989-2003). The site monitored is
assigned to the stage with the highest posterior probability.
For the Nebraska sedge-Baltic rush ecological type the key species are Carex nebrascensis (CANE) and
Juncus balticus (JUBA). 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 two 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: CANE=4500 and JUBA=3000. Four
years later the index values obtained were: CANE=4700 and JUBA=2800. Calculating the probabilities, we
find:
CANE JUBA
LATE
INT
EARLY
Stage
Year1
4500
3000
.101
.896
.003
INT
Year5
4700
2800
.271
.726
.003
INT
Difference
In both years, the site was classified and
assigned to the intermediate seral stage; the
greatest probability values (.896 in Year1 and
.726 in Year5) are associated with INT.
Placement within the intermediate seral stage
is at the upper end of the stage, as indicated by
the second greatest probability values (.101
for Year1 and .271 for Year5) which are
associated with a later seral stage (LATE).
The site shows an upward successional
change of about .17, which is the difference
between the probabilities in Year1 and Year5.
.170
Late
Early
Intermediate
.9
Year 1
1.0
.5
Late
1.0
.5
Intermediate
.73
1.0
Early
Year 5
1.0
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.
.5
Late
1.0
.5
Intermediate
.17
1.0
Early
Change
1.0
.5
1.0
.5
1.0
Page 1 of 4
Monitoring Seral Stages in Nebraska sedge-Baltic rush Ecological Type
Nebraska sedge-Baltic rush Ecological Type by Seral Stages
Mean Index Values of Key Plants
7000
Nebraska sedge
Baltic rush
6000
Index Values
5000
4000
3000
2000
1000
0
LATE
INTERMEDIATE
EARLY
Mean Index
Nebraska sedge
Baltic rush
6,471
655
2,505
3,895
266
448
Mean indices of plant species through three seral stages of succession in a Nebraska-sedge-Baltic
rush 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 Nebraska sedge-Baltic rush Ecological Type
30m
30m
30m
20m
$ 6m
20m
RIPARIAN LIMITS
RIPARIAN LIMITS
TRANSECT
TRANSECT
1. Following one of the layouts above (based on the width of the riparian
habitat as determined by vegetation), establish two 30 m permanent
transects, a minimum of 20 m apart as a plot within the Nebraska
Sedge ecological type. Recommendations are to establish two plots per
section within the ecological type.
2. Using the ‘Nebraska Sedge.xls’ spreadsheet (see figure at left)
installed on your PDA, record canopy cover within a 20cm x 50cm
quadrat for Carex nebrascensis (CANE) and Juncus balticus (JUBA) 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.
Nebraska Sedge.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 Nebraska sedge-Baltic rush 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