Soil properties - CR99

Table 13. Mean cover (%) of the most abundant species

grostis canadensis, and Carex rostrata and Carex

within riverine ecotypes at Ft. Wainwright, central Alaska,

aquatilis occasionally were present.

1998. Blanks in table indicate a species was not present, 0

A companion floristic survey on Ft. Wain-

indicates cover <0.5%, and bolded values indicate fre-

wright performed by Racine et al. (1997)

quency of occurrence is >60% within an ecotype.

found 491 vascular plant species (including

subspecies and varieties) and 215 species of

ground-inhabiting cryptograms, including 95

mosses, 109 lichens, and 10 liverworts. The

inventory found 11 species of rare vascular

plants that are being tracked by the Alaska

Species

Natural Heritage Program, but none of these

taxa are listed by the U.S. Fish and Wildlife

Ptilium crista-castrensis

5

Pleurozium schreberi

9

3

Service as endangered or threatened. The

large floristic diversity on Ft Wainwright re-

Peltigera aphthosa

0

1

flects the large size of the study area and wide

Linnaea borealis

1

15

range of climatic, geomorphic, and hydro-

Rhytidiadelphus triquetrus

Hylocomium splendens

A comparison of soil properties among

Mertensia paniculata

0

2

ecotypes reveals large differences in perma-

frost occurrence, surface organic depth, depth

to gravel, pH, electrical conductivity, and

Equisetum arvense

5

14

18

water depth (Fig. 26 and 27). Ecotypes were

Epilobium angustifolium

0

1

6

grouped by physiography to facilitate com-

Polytrichum sp.

0

1

parisons.

Calamagrostis canadensis

2

1

21

16

31

Permafrost almost always was present in

Alnus tenuifolia

5

30

1

31

Betula papyrifera

3

15

1

29

lowland ecotypes, except Lowland Moist

Populus balsamifera

10

1

35*

Meadow, Lowland Gravelly Moist Mixed

Salix bebbiana

1

11

16

Forest, Lowland Gravelly Wet Tall Scrub,

Salix arbusculoides

0

14

Lowland Bog Meadow, and Lowland Fen

Vaccinium vitis-idaea

5

Meadow. Permafrost almost always was absent

Empetrum nigrum

5

1

Galium boreale

1

0

1

in the riverine ecotypes. Permafrost usually

Salix alaxensis

6

was absent in upland ecotypes, except for

Rubus idaeus

0

3

Upland Wet Needleleaf Forest, which was fro-

Carex rostrata

1

38

zen in one-third of the plots.

Potentilla palustris

3

1

Surface organic matter depths (unin-

Equisetum fluviatile

10

terrupted O horizons at the surface) were

Sample size

4

2

9

4

greatest in the Lowland Bog Meadow and

*A common species, but encountered in only 2 of 4 plots.

Lowland Fen Meadow that develop after

thermokarst. Most lowland ecotypes also had

and Potentilla palustris, with Myrica gale and C.

relatively thick organic layers, with mean thick-

calyculata often present.

nesses ranging between 20 and 40 cm. In contrast,

Lowland ecotypes had four classes dominated

riverine and upland ecotypes usually had mean

by graminoids and forbs (Table 12). Lowland Fen

organic thicknesses <15 cm, except Upland Wet

Meadow was dominated by Menyanthes trifoliata,

Needleleaf Forest, which had a mean thickness of

Equisetum fluviatile, and Potentilla palustris. Lacus-

16 cm.

trine Fen Meadow was similar, except Eriophorum

Depths to gravel were highly variable among

russeolum was more common, as were the shrubs

ecotypes. Reliable comparisons were made more

Chamaedaphne calyculata and Potentilla fruticosa.

difficult, because depth to gravel frequently was

Lowland Bog Meadow was dominated by Sphag-

not determined when it occurred at depths greater

num spp. and Carex aquatilis, and the dwarf shrub

than the soil pit, or when the presence of perma-

Oxycoccus microcarpus usually was present. Low-

frost limited probing for gravel. In general, how-

land Moist Meadow was dominated by Calama-

ever, depth to gravel was deepest in the Lowland

51

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