Ecological Classification System Levels

LAND TYPE ASSOCIATION
Land Type Associations (LTA's) are subdivisions of Subsections defined by similar patterns of characteristics such as:
 


Figure 18 shows LTAs that have been developed in the Chippewa Plains Subsection.

                                           Figure 18

Figure 19 shows the status of LTA development in Minnesota.

                                          Figure 19

An example ( illustrated with satellite imagery ) of LTA development - The St. Croix Moraine

The St. Croix Moraine  is located in central Minnesota close to the town of Brainerd (Figure 20).


Satellite

                                           Figure 20

Satellite imagery was used to create the next few images; the shading of the images was adjusted to draw out the features being discussed. 

 Vegetation

Figure 20 shows striking differences in vegetation on the different LTA's in this area. The St. Croix Moraine is dominated by forested vegetation (red color).  Oak and aspen are the dominant tree species.  There are pockets of conifers, mainly red pine and jack pine.  Before the area was settled, white pine was a major component of the forest. 

Topography 

Figure 21 is a map that shows changes in elevation.

Topology

                                            Figure 21

It illustrates some major differences in topography between the St. Croix Moraine and the other LTA's surrounding it.  The St. Croix Moraine is a belt or zone of hills and basins.  The basins tend to be very small and steep sided.  The hills are generally short and can have steep slopes.  Some of the basins are water filled, and others are dry.  When standing in the middle of this LTA, one gets the impression that some very large dump trucks dumped piles of sand, rock and loam to form rounded hills and small depressions.
 

Hydrology 

This LTA has many lakes within its boundaries, but they are quite small.  They average 10 to 50 acres in size. The lakes in shown in Figure 22 are black.

Lakes

                                           Figure 22

There are very few flowing streams in this LTA.  Blue green lines on the image are streams and rivers.  It is very difficult for water to find a path through the very complex topography.  Most of the water flows from the hilltops and settle in the basins.  Notice how the streams and rivers are different on the adjacent LTA's; they are more conducive to water movement. 

Figure 23  illustrates another hydrologic pattern that shows differences between LTA's.

Wetlands

                                              Figure 23

The light blue areas show wetlands across the region.  Note that there are some large and distinctly patterned wetlands to the east and west of the St. Croix Moraine.  The moraine has few small pocketed wetlands.  Most of the wetlands within the moraine have forest communities, dominated by black spruce and tamarack.  Many of the wetlands to the west are dominated by shrub and sedge plant communities. 

Land Use 

Figure 24 shows marked differences in land use across the area.

Land Use

                                             Figure 24

The forested areas are a reddish color  and the agricultural areas are tan or light brown.   This is related to the LTA's.  As stated before, the St. Croix Moraine is dominantly forested.  Settlers tried to farm this LTA, but were quickly frustrated by the poor conditions for farming.  Soils are generally quite sandy and gravelly.  In addition to the poor soils for farming, the topography is hilly, so most settlers moved on to more favorable locations.  Most of this LTA is presently in public ownership and is managed for forest products and used extensively for recreation.  In contrast, the LTA's to the east and west of the St. Croix Moraine have a fairly high concentration of farms.  The soils on these LTA's are not ideal, but the topography is flatter and the land is more suited for agriculture.

The Gutherie Till Plain 

The Guthrie Till Plain LTA (Figure 25) (part of the Chippewa Plains Subsection) is a relatively level plain with loam & clay loam soils.

                                           Figure 25

The Guthrie Till Plain unit is dotted with three lakes and numerous streams.  Water runoff moves through the upper layers of the soil, but a lower "clay hardpan" layer prevents the runoff from reaching the lower bedrock layers.  The water eventually emerges to the surface as seeps up into intermittent streams or black ash swales. 

The Guthrie Till Plain was once dominated by hardwood and pine/hardwood forests.  This unit had periodic fires, usually started in adjacent droughty sand plains to the north, that helped create forest communities dominated by white pine, red pine or pine mixed with hardwoods.  European settlement brought intensive logging and agriculture to northern Minnesota and changed the Guthrie Till Plain's landscape.  Presently, the unit's forest communities are dominated by aspen and paper birch with some pine.
 

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