The Floristic Quality Index (FQI) has become a widely used
measurement of natural areas quality. This standardized tool was developed by
Floyd Swink and Gerould Wilhelm at the Morton Arboretum, and is explained in
detail in their book: “Plants of the Chicago Region”, published by the Indiana
Academy of Sciences. FQI is not a stand-alone value, but is used together with other assessments to
evaluate the quality of a site.
Measuring the FQI begins with an assemblage of a complete
species list for the site. Each species is assigned a unique Coefficient of
Conservatism (a number from 0 to 10), which expresses the probability that this
plant species is likely to occur in landscapes relatively unaltered from those
of pre-settlement times. Plant species with high C values are relatively
specialized in their requirements, and are thus found in more restricted
habitats.
C values are assigned to species on a state-wide basis, and
the C values for Wisconsin plants can be found in an extensive publication
edited by Thomas Bernthal issued by the Department of Natural Resources.
FQI is calculated by multiplying the mean C value for a site by the square root of the number of species at that site. (As far as I can determine, Swink and Wilhelm have not explained the basis for this formula. Why, for instance, square root of number of species?)
Since 2002 I have been keeping detailed records of plant
species at Pleasant Valley Conservancy. This year Amanda brought together all
data from 2002 through 2015 (13 years),
sorted them by management unit, and then applied the C values and made the FQI
calculation for each unit. The table below provides the data, sorted by FQI
(highest on top). Also given in the table is the acreage and total number of
species for each unit, and a brief description of its ecological character. The
location of each unit can be found in the Management Map found at this link.
The single highest FQI was in Unit 6, an outstanding hill
prairie/savanna. This unit is a large remnant with a bur oak savanna above and
in the gullies and dry mesic prairie on the lower slopes. Before restoration
had begun this unit, although fairly degraded, had a well developed tallgrass
prairie flora with a big bluestem remnant at the top under the rocks and little
bluestem on the lower slope, and two moderately sized Indian grass patches.
Also, high FQI values were found in Unit 11A, Unit 10, and
Unit 12A, all of which are well-restored oak savannas.
Other units with high FQI values were three of the older and
larger planted prairies (Toby’s, Valley, Pocket) and four of the larger savanna
areas (Units 5, 8, and 12B.
Other high FQI values were found in the larger units (not
surprising, because the larger units in general had more species).
The rest of the data for units at PVC, all with FQI values
over 30, are given in the table below.
|
Name
|
FQI
|
Acreage
|
Total species
|
Present status
|
|
|
Unit 6
|
63
|
4.48
|
153
|
Upper (Bur oak
savanna) Lower (Prairie remnant)
|
|
|
Unit 11A
|
61
|
5.17
|
119
|
Prairie remnant and
bur oak savana
|
|
|
Toby's Prairie
|
61
|
3.63
|
126
|
Dry-mesic prairie
(partially remnant; mostly planted)
|
|
|
Unit 10
|
60
|
2.9
|
136
|
Bur oak savanna
|
|
|
Unit 12A
|
59
|
5.95
|
138
|
White oak savanna
|
|
|
Valley Prairie
|
58
|
3.85
|
130
|
Dry, mesic, and
wet-mesic prairie (planted)
|
|
|
Pocket Prairie
|
57
|
4.5
|
104
|
Dry, mesic, and
wet-mesic prairie (planted)
|
|
|
Unit 7
|
56
|
1.58
|
117
|
Upper (Bur oak
savanna) Lower (Prairie remnant)
|
|
|
Unit 3
|
56
|
1.03
|
105
|
Prairie remnant
|
|
|
Crane Prairie
|
55
|
2.6
|
130
|
Dry, dry-mesic, and
mesic prairie (planted)
|
|
|
Unit 8
|
54
|
1.3
|
102
|
Bur oak savanna
|
|
|
Unit 12B
|
54
|
0.98
|
114
|
White oak savanna
|
|
|
Unit 5
|
52.5
|
1.61
|
105
|
Bur oak savanna
|
|
|
Unit 2
|
52
|
1.6
|
89
|
Prairie remnant
|
|
|
East Basin
|
51.5
|
4.4
|
100
|
Dry-mesic, mesic,
and wet-mesic prairie (planted)
|
|
|
Ridge Prairie
|
51
|
1.67
|
100
|
Dry-mesic prairie
(planted)
|
|
|
Unit 23
|
51
|
0.38
|
93
|
Bur oak savanna
|
|
|
Unit 19C
|
48
|
1.13
|
71
|
Black/bur oak
savanna
|
|
|
Unit 21
|
47
|
3.38
|
75
|
White oak woodland
|
|
|
Triangle
|
47
|
0.55
|
81
|
Hill's oak savanna
|
|
|
Unit 20 combined
|
46
|
3.35
|
86
|
Woods and prairie
mix
|
|
|
Barn
|
46
|
0.48
|
87
|
Wet mesic prairie
(planted)
|
|
|
Unit 9
|
45
|
1.82
|
82
|
Bur oak savanna
|
|
|
Cabin Prairie
|
45
|
0.54
|
83
|
Mesic prairie
(planted)
|
|
|
Unit 1
|
44
|
1.18
|
61
|
Prairie remnant
|
|
|
Unit 11D
|
43
|
4
|
74
|
White oak savanna
|
|
|
Unit 4
|
41
|
0.32
|
48
|
Prairie remnant
|
|
|
Unit 19A
|
40.8
|
0.33
|
69
|
Bur oak savanna
|
|
|
Unit 19B
|
38
|
1.64
|
51
|
Bur oak savanna
|
|
|
Unit 19D
|
35
|
1.05
|
30
|
Bur oak/black oak
savanna
|
|
|
Unit 19E
|
34
|
1.47
|
37
|
White oak savana
|
|
Amanda also made the FQI calculations for Pleasant Valley Conservancy has a whole. There were 335 total species, the average C value was 5.1, and the FQI for the whole Conservancy was 93.21. (This number is much higher than that of any single unit, reflecting the importance of species number in the FQI calculation.)
Another interesting analysis is that of the various planted prairies at PVC. The table below shows, not surprisingly, that the older planted prairies have higher FQIs than the younger ones.
Name
|
FQI
|
Size (acres)
|
Year planted
|
Age in 2016
|
Toby’s
|
61
|
3.63
|
1998
|
18
|
Pocket Prairie
|
57
|
4.5
|
1999
|
17
|
Valley Prairie
|
58
|
3.85
|
2002
|
14
|
Barn Prairie
|
46
|
0.48
|
2002
|
14
|
Cabin Prairie
|
45
|
0.54
|
2002
|
14
|
Crane Prairie
|
55
|
2.6
|
2005
|
11
|
Ridge Prairie
|
51
|
1.67
|
2005
|
11
|
East Basin
|
51.5
|
4.4
|
2009
|
7
|
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