Objectives:  Upon completion of this field trip the student should be able to:

1. to identify species in the listing below
2. to describe some evolutionary survival strategies employed by forest herbs
3. examine impact of earthworms, deer and other invasive species on native plant communities

Introduction:
     The purpose of today's lab is to introduce you to some of the more common forbs that occur in forested areas in central Minnesota.  Once the canopy closes in the springtime, a plant on the forest floor gets very little light.  In fact, no more than 2% of the sunlight that reaches the treetops penetrates to the forest floor.  There are several consequences of this limited availability of light.   Compared to plants that grow in prairies, disturbed areas and other more lighted habitats, herbaceous plants that grow in mature forests after canopy closure:  (1) Are usually less diverse.  Fewer plants are able to tolerate the low-light conditions.  Not surprisingly, oak forests are often better habitats to find woodland wildflowers than a maple-basswood forest because oak forests are usually more open than maple-basswood forests.   This allows for more light penetration to the forest floor and more species are able to take advantage of the additional light; (2) photosynthesize more slowly because of the lower light levels.  However, forest herbs typically utilize light more efficiently - it takes very little light before they reach their maximum rate of photosynthesis; (3) grow more slowly since they have less light available for manufacturing food; (4) have thinner, larger leaves.  The larger leaves act as a bigger antennae to more efficiently harvest the limited light that they receive; (5) tend to be supported by water pressure rather than internal support tissues because the low light conditions limits the amount of nutrients that they can invest in support structures.  Thus, when picked, forest herbs usually wilt more rapidly than plants grown in more open environments.

    St. John's is located in the Eastern Broadleaf Forest Province which extends roughly in a narrow diagonal swath from the SE corner of the statue northwest toward Lake Itasca (Minnesota Department of Natural Resources, 2005).   This region formed a transition between the prairie to west and conifers to the north.  In lab we will visit a forest on campus that is classified by the Minnesota DNR (2005) as a Central Mesic hardwood forest.  Common trees in the area include sugar maple (Acer saccharum), northern red oak (Quercus rubra), basswood (Tilia americana), ironwood (Ostrya virginiana), red maple (Acer rubrum), and green ash (Fraxinus pennsylvanica). 

    The ground layer will be relatively sparse, in large part due to the destructive effect of earthworms and deer foraging.  We will hopefully see many of the species in the listing below.  There are relatively few grass-like plants that grow in these habitats.  We will likely see mountain rice-grass (Oryzopsis asperifolia) and bearded shorthusk (Brachyelytrum erectum) with it pubescent leaf sheaths and leaves that are held at a 90 angle to the stem.  We will observe a variety of clump-forming sedges (genus Carex), most of which will be in a vegetative state making them rather difficult to identify. In addition, there will likely be sugar maple and other tree seedlings.  Among the shrubs that occur here include chokecherry (Prunus virginiana), pagoda dogwood (Cornus alternifolia), gooseberry (Ribes sp.), leatherwood (Dirca palustris) and hazel (Corylus sp.)

Assignment Due Today:

• Wear clothing appropriate for going into the field and bring water, sunblock and bug repellent
• Field quiz

Plants to Know:  (We will locate the following species that will be "fair game" on the PTK quiz/exam.  Other species may also be included.)

 References: