Cottonwood
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
Cottonwood.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 ‘Cottonwood.pxl’ file on your PDA and,
•
Save the file under a new name after finishing data collection on each site, e.g. ‘Cottonwood site1.pxl’, ‘Cottonwood site2.pxl’…….. to avoid overwriting previous files with data.

Monitoring Seral Stages in Cottonwood Ecological Type
Classification, seral assignment, and monitoring of Cottonwood 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: late, late intermediate (LINT), early intermediate (EINT) and early. A site is classified, and assigned to a seral stage by entering a set of key plant measurements 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 (See Cottonwood.xls program for methods).
For the Cottonwood ecological type the key variables are the average diameter (DBH) and the number of
Populus deltoides trees 1 inch and greater (TREES), and the number of P. deltoides trees less than 1 inch in diameter (STEMS) within a 800m
2
plot.
The seral stage assigned to a set of plant measurements 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 basal area and number of trees and stems of Cottonwood on a site resulted in the following values: TREES=186, DBH=3, and
STEMS=107. Four years later the values obtained were: TREES=172, DBH=5, and STEMS=79. Calculating the probabilities, we find:
TREES DBH STEMS LATE LINT EINT EARLY Stage
Year1 186 3 107 .000 .095 .905 .000 EINT
.000 .230 .770 .000
.135
EINT Year5
Difference
172 5 79
In both years, the site was classified and assigned to the early intermediate seral stage; the greatest probability values (.905 in Year1 and .770 in
Year5) are associated with EINT. Placement within the intermediate seral stage is at the upper end of the stage, as indicated by the second greatest probability values (.095 for Year1 and
.230 for Year5) which are associated with a later seral stage, LINT. The site shows an upward successional change of about .14
, 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.
1.0
1.0
1.0
Late
Late
Late
.5
.5
.5
Late Intermediate Early Intermediate
.91
1.0
Late Intermediate Early Intermediate
.77
1.0
Late Intermediate Early Intermediate
.14
1.0
.5
.5
.5
1.0
1.0
1.0
.5
.5
.5
Early
Early
Early
1.0
1.0
1.0
Year 1
Year 5
Change
Page 1 of 4

Monitoring Seral Stages in Cottonwood Ecological Type
30
25
20
15
10
5
0
Average Diameter
Stem Number<1"
Tree Number>1"
LATE L.INTERMEDIATE E. INTERMEDIATE EARLY
Mean Values
Diameter (inches) 25 7 4 3
Stem number <1” 23 38 104 1,938
Tree number >1” 9 76 240 2
Average diameter of cottonwood trees 1 inch or greater, number of cottonwood stems less than 1 inch, number of cottonwood trees 1 inch or greater on 20m X 40m plots through four stages of succession in the cottonwood ecological type. Smoothed lines connect the means for each key plant species at each stage. Graph provides a guide for an approximate mixture of variables at each seral stage.
2250
2000
1750
1500
1250
1000
750
500
250
0
Page 2 of 4

Monitoring Seral Stages in Cottonwood Ecological Type
DATA COLLECTION,
SUMMARIZATION
AND
CALCULATIONS
Cottonwood
DBH
Enter Cottonwood DBH
5
2.4
1.4
3.3
2.5
1.5
2
3.6
1.9
3.4
1.3
1.4
2.7
7.1
3.2
3.4
1.5
10.3
7.5
7.1
9.3
1.2
3.1
7.6
7.8
7.6
8.4
11.3
8.2
9.3
1.2
3.1
1.4
2.7
7.1
1.5
1.5
2
3.6
1.9
3.4
2.2
9
2.2
12.8
5.1
1
7.9
8
9
3.2
3.4
Plot Summaries
TREES DBH
186 3
Enter # of
Cottonwood trees
< 1-inch diameter
STEMS
107
Seral Stage Posterior Probability
LATE LINT EINT EARLY
0.000
0.094
0.906
0.000
Assigned Stage
EARLY INTERMEDIATE
40m 20m
OR
10m 40m
TYPE LIMITS PLOT LIMITS
40m
1. Within the Cottonwood type, establish a permanent plot with an area of 800m x 40m; however, on some sites it may be necessary to use two 10m x 40m plots. (See figure above)
Recommendations are to monitor two sites per section
(640 acres) within the ecological type. Sites should be at least ¼ mile apart.
2. Using the ‘ left) installed on your PDA:
Record the DBH in inches of each Populus deltoides tree 1” or greater in diameter ( DBH ) within the 800m plot.
Record the number of diameter (
Cottonwood.xls
STEMS
2
. Ideal plot dimensions are 20m
’ spreadsheet (see figure at
Populus deltoides
) within the plot. trees < 1”
The spreadsheet calculates the number of trees 1-inch or greater and average DBH of trees for the site. It also provides classification probabilities by seral stage and the seral stage assignment.
‘ Cottonwood.xls
’ Calculations
Average DBH = DBH in inches / number of trees 1 inch or greater.
2
Page 3 of 4

Monitoring Seral Stages in Cottonwood 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.
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