Fergus Falls WMD |
Grasslands
Many species of wildlife require grassland habitats, and in our district nearly 99% of the native tallgrass prairie has been lost to the plow and development. Grasslands provide shelter for birds, mammals, reptiles, and insects. Species like greater prairie chickens, marbled godwits, short-eared owls, bobolinks and other song birds require large tracts of grasslands to make their homes. All species of ground nesting birds like waterfowl, pheasants, and songbirds need grasslands to build and conceal their nests.
The native grass species in the Northern Tallgrass Prairie vary in size from side-oats grama that is about 1 foot tall to prairie cordgrass and big bluestem which can reach 7 feet tall. These plants develop root systems that are sometimes twice as long as the plants are tall. Because of this dense root system, these plants form sod that has a tremendous capacity to absorb run-off and rain water. The plants can take up chemicals and nutrients that are carried into the grassland by run-off thus filtering the water that flows through a tract of grassland.
Grassland Restoration and Management
When a new tract of land is acquired, it has generally been farmed. The District restores the wetlands on the new property, and then seeds the uplands back to native origin grasses and forbs (wildflowers). The District harvests some of the needed seed from local native prairies which are diverse and of local origin. We also purchase some local origin grass and forb seeds to diversify our seed mix. No-till drills are used to seed the grass seed into bean stubble, grass stubble, or burned grass.
A diverse seed mixture is important because the wildflowers provide food for many species of insects. Grassland birds feed on the insects found in these prairies. A grassland tract with diverse species composition can support more wildlife that is dependant on that food source. Plant species diversity also provides variability in the grassland structure. Some wildlife species need dense grasses overhead and passageways near the ground; others like shorter, open areas in a grassland. Plant diversity provides better cover, nesting habitat and food for a larger variety of wildlife species.
Native seedings are managed intensely for about 5 years after seeding. Mowing in the first and second years to control weeds and stimulate growth helps to get the seeding established. Spraying is only done to control difficult patches of weeds. Fire is typically used in the third and fifth years after seeding to help stimulate the production of seed. Once a seeding is established it is difficult for weeds to invade these dense native grass stands with their robust root systems.
Weeds do invade established native prairie and grass seedings, especially where soils are disturbed and seeded plants are sparse. We control some invasive plants with mowing and spraying, but invasive plants can be controlled biologically with insects. Leafy spurge is one invasive plant that can be controlled with its natural insect predator. Flea beetles that feed on the roots of these plants can keep them from growing and may eliminate them completely when conditions are ideal. Research continues on insect control of spotted knapweed and Canada thistle.
When fire has been absent from a tract of grassland for many years, trees and brush can invade. The Northern Tallgrass Prairie on average receives enough rain to support trees, but historically trees did not survive here unless they were near rivers or lakes. Frequent disturbance from fire, bison grazing, and drought allows the prairie community to dominate the landscape. In the part of our district that was historically prairie, we are actively eliminating invasive trees using mechanical cutting and prescribed fire. Tree removal is another tool used to maintain and establish grasslands.
