Natural history - landscape & plant communities

Natural history
Minnesota's geology | Landscape and plant communities | Resources

John Muir once said that any one thing is "hitched to everything in the universe." How then can we look at any one thing without becoming mired in a network of relationships? After years of developing specialized fields of science, how do professionals begin to come together to talk about ecological systems? And how do non-professionals approach an ecological understanding of a resource?

The Ecological Classification System (ECS) is one effort to integrate variables in understanding and describing what's going on in a given area.

The Ecological Classification System (ECS)

A nationwide mapping initiative, the Ecological Classification System, integrates data about climate, geology, hydrology, topography, soil, and vegetation--key ecological factors in determining the character of an area. Then it identifies, describes, and maps land to show its capabilities to support natural resources. This helps us better understand natural areas and their characteristics?plant communities, wildlife habitat, water quality, potential for restoration, and the changes that occur over time.

Biomes (Provinces)

The ECS in Minnesota has identified three major climatic zones, called provinces or biomes. Climate plays an important role in landscape development. Minnesota's climate is affected in the north by Arctic air, and in the south by weather systems from the Gulf of Mexico. There is a division among the biomes, with coniferous forest in the colder northern climate, and prairie and deciduous forest most broadly distributed in the warmer, southern part of the state.

Biomes are large enough to contain localized areas not entirely characteristic of the province itself. For example, a bluff top along a river in the Deciduous Woods may produce a dry "goat" prairie rather than a woodlands, due to its exposure, soils, and drainage. In turn, the Prairie Grasslands biome contains not only prairies, but rivers lined by flood plain forests.

The ECS has further subdivided regional variations within each biome into landscape areas. Landscape areas are described within their biome chapters. The relationships among biomes, landscapes, and individual SNAs are interesting to trace and significant to SNA protection decisions.

SNA site descriptions are arranged throughout this guide by the biomes within which they occur. Within each SNA are found several smaller levels of organization called plant communities.

Plant communities

Plant and animal species flourish or perish, depending upon their environmental conditions. Local groupings of trees, shrubs, grasses, and forbs are called plant communities, and are characterized by the kinds and quantities of species they contain.

Communities are subject to change. The change may be rapid, as after a disturbance, when pioneer species move into the altered environment. As the community develops, it may change the local conditions enough to favor other kinds of species, and a new community succeeds the old. Climax communities, such as the maple-basswood forest, continue to thrive under the conditions they create, and remain stable until disturbed.

Communities serve as the basis for evaluating SNA priorities. Since 1979, the Minnesota DNR's Natural Heritage Program (NHP) has identified, tracked, and prioritized communities and rare species for research and conservation. Minnesota's Native Vegetation: A Key to Natural Communities, version 1.5, contains a description of 57 natural community types and 196 community subtypes. This classification serves as a standard for ecologists as they identify and assess communities. It is useful to anyone wishing to recognize and understand Minnesota's landscapes and our Scientific and Natural Areas.

Distribution and Diversity

Plant distribution varies with factors such as climate, soils and subsoils, landforms, water drainage, and natural disturbances such as fire, wind, insects, and disease.

Many presettlement plant communities were particularly affected by fire. For example, forests reached maturity where fire was prevented by a river or lake, whereas other forests developed into diverse mosaics of old-growth stands, postfire stands, and assorted types ranging in between. At the same time, fire eliminated intrusive species: fire-sensitive species could not survive, while native fire-resistant species did. In this way, fire diversified yet protected the species of plants growing over a broad area.

Human interaction by both American Indians and European settlers has also dramatically affected plant communities. This was most dramatic as settlers converted land to economic production purposes. Wetlands have been drained, prairies plowed, forests logged, and habitat and food chain systems dramatically altered. In the process, we've introduced non-native species such as ragweed, dandelions, loosestrife, buckthorn, and other exotics. Consequently, many native species have been lost or locally extirpated.

The Value of Diversity

Destruction and alteration of forests, native grasslands, wetlands, and water supplies are rapidly reducing our biological diversity. Preserving biological diversity serves many purposes:

• Diversity strengthens and stabilizes natural ecosystems.
• Diversity contributes to the quality of air, soil, and water, which affect all living species, including humans.
• Diverse communities provide untapped reservoirs of genetic materials useful in agriculture, medicine, and industry.
• Natural ecosystems serve as outdoor laboratories for research on plants, animals, and their interrelationships.
• Natural communities provide living museums of our natural world and are sources of beauty, recreation, and inspiration.

The more diverse a community, the greater its resilience. Disruption can take years to repair, and extensive destruction may eliminate the community. To eliminate a single natural community is to eliminate entire chapters of possibility for future development, at the same time eroding the natural system, or "scaffolding," that supports human life.

Minnesota has taken action to ensure preservation of representative natural community examples through the SNA program. Learn to recognize SNA goals and related issues--to value, to support, and to enjoy. They are keys to our future.