Land Cover

Methods

The land cover analysis that follows is based on previous land studies, documented land changes, recorded observations and land use suggestions from a variety of sources. In addition, site visits were conducted during the survey period by staff and volunteers to document vegetation cover and habitat boundaries.

Results and Discussion

Soils

Soils reflect the geological history of the land and help determine how it can be used by plants and animals. Map 3 shows soil types at the Asylum Lake Preserve, in the adjacent study area and on nearby land. The following soil types are shown:

Soil Name Map Abbr.

Dowagiac loam, 0-3% slopes DoA

Houghton and Sebawa soils, ponded Hs

Kalamazoo loam, 0-2% slopes KaA

Kalamazoo loam, 2-6% slopes KaB

Kalamazoo loam, 6-12% slopes KaC

Oshtemo sandy loam, 1-6% slopes OsB

Oshtemo sandy loam, 6-12% slopes OsC

Oshtemo sandy loam, 12-18% slopes OsD

Oshtemo sandy loam, 18-35% slopes OsE

Schoolcraft loam, 0-2% slopes SaA

Spinks loamy sand, 0-6% slopes SpB

Urban land Ub

Urban land-Glendora complex Ug

Urban land-Kalamazoo complex, 0-6% slopes UkB

Urban land-Kalamazoo complex, 6-12% slopes UkC

Urban land-Oshtemo complex, 12-25% slopes UoD

Water w

Historic Land Cover

The entire Asylum Lake property, with the exception of Asylum and Little Asylum Lakes and some surrounding marsh, was once under landcover listed by the Michigan Natural Features Inventory (MNFI) as mixed oak savanna. In fact, much of the area now occupied by the western half of the City of Kalamazoo was an extensive oak savanna, part of a Michigan prairie complex covering slightly more than 80,000 acres at the time of European settlement. These prairies were scattered across the southern Lower Peninsula, mostly in the southern three tiers of counties. In addition, much of the oak-dominated area of southern Michigan resembled savanna rather than forest.

These “oak openings” or oak savannas were extensive in the southern Lower Peninsula, particularly in the southwest. It must be noted, however, that the early surveys provide only a snapshot of these constantly changing systems (Comer 1995). Mixed oak savanna is probably a composite of three Michigan Natural Community Types as classified by the MNFI: bur oak plains, oak openings, and oak barrens. These

communities represent a full spectrum of water-retention capacity and neutral to medium acidity. All were on level to gently undulating ground with mostly loam or sandy loam soils. The widely spaced canopy consisted of a few species of oaks—bur oak (Quercus macrocarpa), white oak (Q. alba), black oak (Q. velutina), red oak (Q. rubra), and scarlet oak (Q. coccinea)—and also hickories (Carya spp.). In the herbaceous layer were many genera characteristic of the mesic and woodland prairie, such as bluestem

(Andropogon), sunflowers (Helianthus), lead-plant (Amorpha), cord grass (Spartina), rosinweed (Silphium), vervain (Verbena) and goldenrod (Solidago).

The Role of Fire

Fire played a large role in maintaining the North American grasslands. Wright and Bailey (1981,1982) estimate a 5-10 year average for fire frequency of North American grasslands. The effects of fire on vegetation and birds vary with moisture conditions and seasons (Higgins et al. 1989; Wright and Bailey 1982). Fire probably occurred more frequently (every 6 years) in the northern mixed prairie, and much less so (every 25 years) in the dry western part of the mixed prairie (Bragg 1995).

Oak forests subject to fires produce a bur oak-savanna system, in which bur oak persists as oak grubs, tenaciously re-sprouting after fire. Many early settlers describe the difficulty of removing these oak grubs as they began to farm the lands. Topography also played a part in the changing vegetation cover, with bur oak plains on level or undulating ground and beech-maple forests generally displaced to irregular ground, presumably outside the path of regular fire.

The oak grassland region of southern lower Michigan, while highly dynamic locally, was probably stable overall, so long as climate did not change (or Europeans arrive). Under the appropriate burning regime, prairie and savanna would have been permanent features of southern lower Michigan. (Chapman 1984).

All of the original oak savannas have either been converted into agricultural land or have become closed canopy oak forests due to fire suppression. Fire suppression within remnant oak hickory forest has limited further regeneration of oak species.

The Role of Fragmentation

Most of Michigan’s forests and grasslands, like those at Asylum Lake, are highly fragmented and do not provide the large, contiguous areas required to sustain populations of many forest and grassland bird species. These fragmented habitats also contribute to higher rates of nest failure for bird species unaccustomed to nesting in such landscapes.

Excessive edge habitat is widely considered detrimental to the nesting success of forest birds because of increased concentrations of predator and parasite populations (Wilcove 1985; Terborgh 1989). Brown-headed Cowbirds (Molothrus ater) historically foraged in the wake of migrating bison, infiltrating relatively short distances along prairie edges. However, they have adapted well to confined cattle pastures and the forage provided by agricultural fields, placing an even greater pressure on pasture and edge nesting species.

Some nest predators are more common and can be more effective in fragmented landscapes. Small woodlots in agricultural landscapes have high populations of raccoons (Casorati et al. 1993). Higher predation rates of ground, near-ground and even

higher open-cup nesting birds in the most fragmented landscapes may reflect the abundance of Blue Jays (Cyanocitta cristata) and American Crows (Corvus brachyrhynchos) (Gibbs and Faaborg 1990; Villard et al. 1993; Porneluzi et al. 1993). Fragmentation also impacts other animal populations and suppresses the natural processes that maintain plant diversity.

The Effect of Agricultural Lands

Row Crops

Over the years, much of the southern area of the Asylum Lake Preserve was used to grow agricultural crops. While some agricultural practices closely mimic the cover and resources provided by native grassland ecosystems, the production of extensive monoculture fields, especially corn or soybeans, and frequent disturbances of agricultural habitats pose new threats to grassland or open field birds. Machinery, used

for harvest and maintenance during the breeding season, can destroy nests dramatically lowering the nesting success of populations occupying these habitats.

Although corn is an important winter resource for resident grassland birds such as Ring-necked Pheasant (Phasianus colchicus) and Northern Bobwhite (Colinus virginianus), corn and soybean fields are ecological traps for many birds, where productivity is well below levels necessary to sustain populations (Rodenhouse and Best 1983; Basore et al. 1986; both cited in Stallman and Best 1996). In general, monocultural land practices reduce the diversity of populations of both vertebrate and invertebrate species. In addition, row crops and associated agrochemicals negatively impact plant distribution and diversity.

Non-Row Crops

While non-row crops such as wheat, oats and barley can provide adequate cover and food for many grassland bird species, only a few bird species actually nest in these areas. Red-winged Blackbird (Agelius phoeniceus), Bobolink (Dolichonyx oryzivorus), Horned Lark (Eremophila alpestris), Vesper Sparrow (Pooecetes gramineus) and Savannah Sparrow (Passerculus sanwichensis) utilize these fields in the midwest. In general, when these fields are harvested late enough to avoid the peak nesting season, they may serve as suitable adjacent habitats or buffers in agricultural landscapes (Sample and Mossman 1997).

Hayfields and Pasturelands

Many species such as Henslow’s Sparrow (Ammodramus henslowii), Eastern Meadowlark (Sturnella magna) and Bobolink have adapted to breeding in agricultural hayfields and pastures. In fact, establishment of rangeland and pastureland may have benefited nesting birds when overgrazing and overly frequent harvesting are avoided. Hayfields, once consisting primarily of timothy and clover, were mown in late June, then left to dry prior to bailing, giving time for Bobolink, Eastern Meadowlark and many sparrows to raise their broods. However, as many of these late-harvest natural pasture grasses are converted into faster growing alfalfa fields, grassland birds have suffered lower nesting success. Although alfalfa fields attract a wide variety of species, they best serve early nesters, such as the Vesper Sparrow and Red-winged Blackbird, and can be an ecological trap or sink habitat for later nesters. However, even the Redwinged Blackbird suffers heavy mortality of young in alfalfa fields.

Surveys of Michigan grassland birds show more than 75% of the species declining throughout most of the state. Grassland bird populations naturally fluctuate geographically and temporally (Robbins et al. 1996); however significant alteration and loss of breeding habitat are suspected causes of continent-wide population declines of these grassland nesting species (Knopf 1994). In addition, few native butterflies benefit from alfalfa and large numbers of white-tailed deer fawns and other vertebrates die as a

result of mowing alfalfa fields.

Present Land Cover

As the old farm and orchard lands undergo succession towards a more natural state, some aggressive plant species have colonized these non-forested areas on the Asylum Lake property. The more densely arboreal compartments, Old Orchard and Old Fields D and E, may currently resemble, from a distance, a savanna, or even marginal woodland, due to the density of apple trees in some areas. It is interesting to compare this with James Fenimore Cooper's description published in Oak Openings in 1812:

...the trees were of very uniform size, being little taller than pear trees...and having trunks that

rarely attain two feet in diameter...in places they stand with regularity resembling that of an

orchard, then, again, they stand as copses, with vacant spaces, that bear no small affinity to

artificial lawns, being covered with verdure. (Comer 1995)

The herbaceous layer in most of the old fields and old orchards on the Asylum Lake property is dominated (or at least co-dominated) by brome and other grasses, which forms a nearly impenetrable layer of spreading roots. A few other resilient species, mostly nonnative, are prevalent.

Farm Field A and Old Field A have been altered since the survey was undertaken, but vegetation noted in these compartments is still relevant. These areas were treated with herbicide and mown in the fall of 2000 by WMU employees in preparation for their upcoming restoration to mesic tallgrass prairie and oak savanna. Seventeen bur oak (Quercus macrocarpa) have been planted in Old Field A and a few elms (Ulmus spp.) and other trees have been cut. At least one population wild indigo (Baptisia sp.) was

sprayed during the treatment, plants that should have been moved.

The most common plant species in Farm Field A were as follows: Queen Anne’s lace (Daucus carota), showy goldenrod (Solidago speciosa), Canadian goldenrod (Solidago canadensis), white sweet-clover (Melilotus alba), and blackberry (Rubus allegheniensis). Due to their seed and root density, and sometimes their overall resilient nature, some of these species may be resistant to some effects of herbicides and mowing. Other less common but similarly resilient plants include burdock (Arctium sp.), thistle (Cirsium

sp.), spotted knapweed (Centaurea maculosa) and poison-ivy (Toxicodendron radicans).

Old Field A shows similar characteristics and also will have a persistent seed bank and root mass of a few more common species. These are spotted knapweed, Queen Anne’s lace, Canadian goldenrod, early goldenrod (Solidago juncea), flat-topped goldenrod (Euthamia graminifolia), multiflora rose (Rosa multiflora), blackberry and wild black cherry (Prunus serotina). Other plants (less common) that may persist as a product of life history traits are burdock, thistle, red-osier dogwood (Cornus stolonifera), staghorn sumac (Rhus typhina), and box-elder (Acer negundo). Some invasive and/or secondary successional species from the surrounding Forest A may also creep in or rain seed on these compartments.

Old Field B supports these very common plant species: red clover (Trifolium pratense), yarrow (Achillea millefolium), spotted knapweed, gray goldenrod (Solidago nemoralis), white sweet-clover, black raspberry (Rubus occidentalis), English plantain (Plantago lanceolata), blackberry, poison-ivy, enchanter’s nightshade (Circaea quadrisculata) and Virginia rose (Rosa virginiana). Old Field B is situated on considerably more rolling ground than the previous compartments and, as a pocket of grassland between two tracts of forest, it is surprising that it is not more dominated by successional forest species. There are some autumn olive (Eleagnus umbellata), tartarian honeysuckle (Lonicera tartarica) and glossy buckthorn (Rhamnus frangula) on the fringes, and these will undoubtedly continue to move toward the center.

Flat-topped goldenrod, gray goldenrod, rough-leafed goldenrod, red-osier dogwood and staghorn sumac are the most common plant species in Old Field D. Old Field E is dominated by flat-topped goldenrod, gray goldenrod, rough-leafed goldenrod, blackberry, red raspberry and red-osier dogwood. Old Orchard has a diversity of common species: yarrow, Queen Anne’s lace, gray goldenrod, showy goldenrod, selfheal (Prunella vulgaris), goosegrass (Galium aparine), small-flowered buttercup (Ranunculus abortivus), purple dead nettle (Lamium purpureum), common blue violet (Viola papilionace), tartarian honeysuckle, Virginia creeper (Parthenocissus quinquefolia), multiflora rose (Rosa multiflora), blackberry, poison-ivy, ground ivy (Glechoma hederacea), box-elder and apple (Malus pumila). These three compartments can be considered as one contiguous area, though partially broken up by Forest E, which extends into the area as a peninsula. Only the Old Orchard parcel contains apple trees, but the whole area seems commonly linked by oaks. Bur oak and red oak appear most commonly, although no bur oak appears in Old Field D, a sliver of a compartment on the border of the whole area. A somewhat regular scattering of box-elder, wild black cherry, red elm (Ulmus rubra) and black walnut (Juglans nigra) throughout the (non-native) grassland is reminiscent of the presettlement community type believed to have occurred on this property, especially with the prevalence of bur oak, a dominant species of the bur oak plains. This is the only compartment (or group of compartments) resembling any of the Michigan Natural Community Types.

Grassland, Prairie and Oak Savanna Management

Because Michigan is at the northernmost range of the historic occurrence of tall-grass prairie (Transeau 1935), native grasslands and savanna are in an ecologically precarious position, making them sensitive to small shifts in disturbance patterns that would allow other vegetation types to dominate. Competition from introduced grasses and invasion of woody vegetation, particularly Rhamnus and Lonicera species, pose a threat to these systems (Hanaburgh 1995).

Grassland species evolved in a habitat that was the product of regular natural disturbances. Therefore, preservation of grassland avifauna or grassland ecosystems requires either allowing these natural factors to operate or having managers create similar conditions. Implementing management that perpetuates the unique characteristics of these systems may also improve habitat for grassland wildlife species (Hanaburgh 1995).