Comparing the Presence of Indigenous and Exotic Species in a Plant Community
Trudy Hyde, Delaware State University
Objectives Identify plant species (native & exotic), measure the flora coverage of each species and describe the geological effects on the over all plant coverage.
Suggested Grade Level and Discipline Grades 8-12 Biology Earth Science Environmental Studies Earth Science Syllabus Area 1 Topic I (Observation and Environment)
Behavioral Objectives *Upon completion of this project students should be able to: a. Collect and identify common plant species, native and exotic. b. Measure flora coverage of each plant species. c. List and describe geological factors that can influence plant distribution. |
Major Understandings A plant community is an assemblage of naturally occurring plant species living in the same environment and interacting in many ways. There are exotic plant species that are able to disrupt the natural balance of a community of native plants. Measuring the flora coverage yields useful information such as the relative abundance and dominance of different plant species in an area. The structure of plant communities in a forest area consists of a vertical stratification (layers of vegetation) of plant life. Plant distribution can be influenced by geological factors such as soil and topography (slope, lowland etc.).
Materials *Background Information Sheet *Vocabulary Sheet *Procedure Sheet (getting started) *Materials Sheet *Data Sheet #1 and #2 |
Background Information
| Plant Community Plants are a very important and fundamental unit of our environment. The forest contains some of our most valued plant communities. A plant community is a group of interacting plants inhabiting an area. The community is composed of a wide variety of plants that interact or compete for space, soil, nutrient, sunlight and even shade. Thus, the community of plants exist with the natural and orderly progression of biological changes. However, there are plant species that can upset or offset the balance of the plant communities in a forest. These plants are termed exotic, non-native, or more specifically "invaders". What is an Exotic or Nonnative Plant? Exotic or nonnative plants are foreign species of plants that are from other areas or countries. Some of these species of plants have been accidentally introduced in the plant community, some have escaped from cultivation, and others have been purposely introduced in plant communities (sometimes resulting in great consequences). What is an Invader? Specifically, an invasion occurs when a plant community of indigenous species becomes overrun or infested with exotic plant species. These exotic plants may enter areas of a relatively balanced plant community and dominates its resources, even to the point of completely displacing these plant communities. Exotic or nonnative plant species that interact in such a manner are appropriately termed "invaders". |
Species Dominance Dominance in a plant community may refer to the most abundant species that possess the highest biomass, occupy the most space, make the largest contribution to energy flow or mineral cycling, or have other means of control or influence on the plant community. However, the most abundant plant species are not necessarily the most influential members of the plant community. Differences in the environment of plant communities, such as moisture availability, nutrient level, soil, and topographic positions, can influence plant distribution and dominance. Measuring the proportion of basal area comprises one method of measuring plant coverage or relative dominance. Vertical Stratification It is important to consider the different levels of vegetation when measuring plant coverage or determining species dominance. A plant community consists of physical layers of vegetation. This physical structure is a vertical stratification of several layers of vegetation. Starting from the top, the layers are the canopy, the under-story tree layer, the herbaceous or ground layer, and the forest floor or litter layer. An open canopy yields a well developed shrub layer and under-story tree stratum, and this is particularly due to the sunlight that is able to reach other layers of the vegetation. A closed canopy yields poorly developed under-story trees, shrubs and often the herbaceous layer. The soil moisture, the density of the over-story, slope position (hilly and mountainous regions), topographic positions, and disturbance, all have an influence on the nature and development of the layers of plant stratification. |
Procedure 1. Introduce background information on plant life or plant community. |
References
Mooney, H .A., Drake, J. A., Ecology of Biological Invasions of North America and Hawaii. |
Materials
*Field Guides for identifying plant species (Guide for trees, shrubs, wildflower & other plants. Plants can be pressed for an herbarium).
*Measuring Tools
-meter stick (with smaller unit of measurements for small
plots).
-measuring tape (preferably in meters).
-stakes (four needed)
*General Tools
-Any form of thin rope or string for sectioning off area (brightly
colored yarn works well).
-Calculator
-Mathematical formula for calculating area (square, rectangle,
circle, triangle).
-One-hole hand puncher for marking vegetation that has already been
measured.
(saplings and plants in poor condition
should not be marked using this method.
However, feel free to use other less damaging
methods for marking vegetation).
Glossary
Biomass: Weight of living material, usually expressed as dry weight per unit area.
Dominance: control within a plant community over the environmental conditions (sunlight, space, etc), thereby influencing the type and abundance of other plant species in the community.
Plant Community: A group of plants naturally inhabiting and interacting in the same environment.
Disturbance: Any physical force, such as wind, fire, flood, extreme temperatures, and epidemic that can damage natural plant communities or natural systems and result in mortality of organisms and loss of biomass. (disturbance can be natural or human inflicted).
Exotic Plants: Plants that are from other areas or countries.
Indigenous/Native: An original inhabitant or resident.
Invasive Plant: Plants that have the ability to invade and disrupt or displace a relatively intact plant community.
Getting Started
Step #1: Conduct an overall survey of the plant species that are present in the forest or area of study.
Method: Collect leaf samples for identification of plant species. Determine other ways of identifying plant species consists of observing the fragrance, tree sap, and features of tree bark. Leaves should be pressed for preservation and an herbarium can be constructed.
Step #2: Choose and measure sites for study. Select different types of sites for study. Sites should be chosen based on specific geological features. Measure the entire area of chosen sites and section each site off.
Method: A visual observation of the landform should be conducted in order to choose the three sites.
Examples of geological features that can be used for project
1. Leveled ground (water content in soil is medium).
2. Lowland (predominantly moist or wet soil).
3. Slope (soil is mostly dry or well drained).
Once the sites have been chosen, determine how large of an area you are able to complete. (Remember there are different vegetative layers that you will be working with and this takes time). Begin by choosing a tree or stationary object as reference point. Measure an area of a square or rectangle (this is easier to work with). Record the measurements of each site. To keep track of the measured area, outline it with a visible rope or string.
Step #3: Determine the coverage (flora) of the plant species present at each site.
Method: Flora coverage can be determined by choosing one or more plant species and measuring the area it covered. However, flora coverage often forms different shapes so the area of the shape should be calculated using different formulas. Once the measurements are recorded, estimate the proportion of the flora coverage for that area. Two different procedures can be used to measure flora coverage.
1). Species flora coverage = (Area of plot) X (estimated proportion of flora coverage of the species).
Area = 15 square meter
For example: Calculate the area of the plot (in this case it is a rectangle) then carefully look at how much the area is covered by the flora of the species you are looking at and estimate the proportion of the area covered by that species. The estimated proportion of this rectangle is about 50% coverage. The calculations are as follows:
Species coverage = (15 sq.m X .50 ) = 7.5 square meters
2) Plants with leaves that are scattered or isolated.
Measure the area of one leaf (leaf average is more precise) and multiply it by the number of leaves counted.
For example: Species flora coverage = Area of 1 leaf x 5 leaves.
Step #4: Mark or indicate vegetation that has been accounted for.
Formulas for Measuring the Area of a Plot Shape
Areas
Data Sheet for Plant Coverage
Chart #1 Geological Location:___________________
| Common Name |
Proportion of species coverage (%) |
Type of Plot | Length/ Diameter |
Width | Number of Leaves |
| Spicebush | 25% | Rectangle | 4m | 2m | |
Data Sheet for Plant Coverage
Chart #2 Geological Location:________________________________
| Common Name | Scientific Name | Native Species | Exotic Species |
Total Coverage of Each Species |
|
| Spicebush | Lindera benzoin | X | 2.5 m (square) | ||