Old Fields and Disturbed Land
The purist would probably include 90 % of Cedar Creek in the disturbed
category. The cynic would probably say 'show me something undisturbed'.
Very little of the Area has escaped the hand of man. Considerable
areas of upland were cleared for agriculture. Most of the upland
woods were pastured or logged. Part of the creek and some wetlands
were dredged. Natural fires were suppressed. Although most of these
practices have been discontinued, their effects are still visible.
An obvious one is the rectangular margins of our abandoned fields.
A less obvious example of past disturbance still visible today is Juniper
Savanna. This tract of beautiful open-grown bur oaks was heavily
grazed by cattle until the early 1970's. The cattle ate everything except
the unpalatable bush juniper (Juniperus communis) which eventually
came to dominate the understory to the exclusion of all else. This
juniper savanna may be interesting to look at, but it is still not well.
Among the more obvious signs of disturbance are fields abandoned from
agricultural use, pine plantations, roadsides, ditches, canary grass wetlands,
gardens and homesites, and experimental plots. Of 113 species
of introduced plants found on the area, fully 90% occur primarily/solely
on such disturbed land.
Old Fields
CCNHA contains more than 100 fields that have been abandoned from agriculture.
These range in age of abandonment from 1927 to the present. (Perimeter
fields that are now farmed are periodically released from cultivation so
that a chronosequence of abandoned land will always be available for study.)
A few of the oldest fields have reverted to sand prairie. These occur
in some of the Burn Units in the southern half of Cedar Creek and are discussed
in the Section on Sand Prairie and Savanna.
Several fields were planted in the European perennial Bromus inermis (Smooth Brome) in the 1950's and are still dominated by this grass.
Examples include: HUT, RSW, PMN... Abandoned fields not included
in the Cedar Creek Burn Program occur primarily in North Section. Poa
pratensis, Agropyron repens, Setaria glauca, and Carex foenea are the four dominant graminoids of most of these fields. A few of
the fields in North Section that were abandoned in the 1950's are now dominated
by Schizachyrium scoparium (Little Bluestem). Although woody
invasion of abandoned fields at Cedar Creek is extremely slow, several
of these 'Schiz fields' have been invaded by White Pine from surrounding
upland forests. Examples include: B, BGS, LBS... Pocket gopher mounds and badger diggings are a common sight in Cedar Creek old
fields.
Fields last cultivated in the 1970's or more recently retain a weedy
character. Poa pratensis (Kentucky Bluegrass), Agropyron
repens (Quackgrass), Setaria glauca (Yellow Foxtail), Digitaria
ischaemum (Crab Grass), Agrostis alba (Redtop) are five common
completely naturalized exotic grasses.
Common weedy forbs, many of them introduced
species, include: Ambrosia artemisiifolia (Ragweed), Polygonum
convolvulus (Bindweed), Conyza canadensis (Horseweed), Verbascum
thapsus (Mullein), Berteroa incana (Hoary Allysum), Lepidium
densiflorum (Peppergrass), and Chenopodium spp (Lamb's Quarters).
A more complete listing is provided in the accompanying Table.
Pine Plantations
Several Pinus strobus and P. resinosa (White and Red
Pine) plantations were established in the 1950's. Most occur near
residences (South House Pines, Bur Oak Pines, Beckman Lake Pines, Lundgren
Pines). These were planted rather densely, have an acidic needle
duff, and very little in the way of a ground flora. Pinus sylvestris (Scotch Pine) is a common windbreak tree planted along roadsides and between
fields.
Homesites and Gardens
Conspicuous elements here are tree plantings, ornamentals,
and garden plants. Most rarely escape the homesite. Two species
of trees that are exceptions are Ulmus pumila (Siberian Elm) and Robinia
pseudoacacia (Black Locust). Siberian Elm has invaded the succession
strips and is found in LCfield. Black Locust has invaded fields
and woods off the SE corner of Fish Lake. Robinia hispida (Prickly Locust) is found near the old Lundgren homesite, Caragana arborescens (Siberian Pea) is found near Corneia's Cabin, Spiraea van-houttei is found at the Heckenlaible homesite, Syringa vulgaris (Lilac)
is found at several homesites, and Sorbaria sorbifolia (False Spiraea)
occurs near the Lab. Other woody species restricted to homesites
include: Picea abies, Picea pungens, Picea glauca, Acer saccharinum... Common ornamental forbs confined to homesites include Hemerocallis fulva (Day Lily), Convallaria majalis (Lily of the Valley)...
Roadsides and Ditches
The mowing of roadsides has enabled several species of roadside
weeds to become established. Included in this group are: Circium
arvense (Canada Thistle), Sonchus arvensis (Sowthistle), Medicago
sativa (Alfalfa), Melilotus spp (Sweetclovers), Trifolium
arvense (Rabbitfoot Clover)....
Reed Canary-grass Wetlands
This is an unnatural community created by draining other wetlands and
seeding them with the exotic and now fully naturalized Phalaris
arundinacea (Reed Canary Grass). These were mowed for meadow
hay following the drought years of the 1930's, but are generally now ignored
as forage or even pasturage. Enormous tracts occur throughout the
Anoka Sandplain, especially on Carlos Avery WMA. Fortunately, Cedar
Creek has very little of this community type. The largest 'unnamed'
example lies off the southeast shore of Fish Lake.
Experimental Plots
When Cedar Creek became a Long Term Ecological Research (LTER) site
in 1982, portions of several of the Area's old fields were 'Zoned' for
experimental work. (See GIS and Experiments for exact locations.)
Major Disturbance Areas have been confined to fields A, B, C, D, and E.
Much of this work has examined the effect of N-fertilization or disturbance
(eg. burning, roto-tilling) on old field communities. Macroplots (measuring 20x50 meters) were established in 1982 in fields A, B,C, D and
fertilized at varying intensities until 19xx. Fenced areas containing
numberous fertilized microplots (4x4 meters) were established in
these same fields in 1982 and continue to be maintained. A set of Herbivore
Exclosures were set up along the perimeter of BLN in 19xx. Solidago Transplant
Gardens have been established in A, B, BP and BDG. Functional Group
Gardens were established by Amy Symstad in field C. Experimental
Gardens were created in BP, BDG, BioCON and these have drastically
altered the appearance of these areas. The topsoil was removed
by earth-moving equipment to reduce soil-banked seeds before the experimental
gardens were established. The seeds used in these gardens were purchased
from commercial sources rather than being harvested locally. Species
selected for these experiments have generally been native to the Area,
but exceptions have occurred. Most notable are Bouteloua gracilis,
Buchloe dactyloides, Monarda punctata... The seeds of ca. 30 prairie
species were added to plots in Field D in 1988 artificially increasing
the diversity of this savanna. Several of the species added (eg. Baptisia,
Lupinus, Zizia) did not occur there previously.
Work confined to Minor Disturbance Areas is anticipated to have only
minimal long-term impact. Such work would include erecting small
temporary exclosures, marking plants, etc. Most areas on CCNHA are
available for this sort of study. (See Research Protocol.)
