Forest Community

Principles of Ecology BIO 3614

Forest Ecology Lab

Part 1: Forest


For this assignment: we will collect abiotic and biotic data in the Kennedy reservation.  You will use this data to write a scientific research paper.  The paper will have an abstract, introduction, methods, results, discussion, and literature cited section.



Forest communities cover approximately 50% of the North American continent, and they provide valuable habitat for a large number of animal species, as well as a variety of commodities for human consumption (lumber, maple syrup, fungi).  Deciduous forests are composed of trees which drop their leaves in autumn in the temperate regions and during the dry season in more tropical areas.  Coniferous forests are composed of cone-bearing trees that retain their leave through the winter.

Forests are also classified by how they have been impacted by human development or major disturbance.  Virgin (primary) forests refer to an area that has reached maturity (natural succession) without human influence.  Virgin forests can be old growth (never been logged) or they can be without human influence for over 60 years.  Virgin forests are characterized by trees of various ages (must have old trees) and with the presence of fallen logs on the forest floor.  Virgin forests tend to have a more open space at the ground level and areas of regeneration in gap spaces.  Virgin forests are vastly different from second growth forests, which develop after a virgin forest undergoes a disturbance, such as clear cutting or intense fire. A secondary forest is typically composed of even age stands (all trees are the same age), which results from regrowth of seeds after the disturbance.  These forests typically have high tree densities with less understory development.  Continued succession (undisturbed time) however will lead to uneven aged stands which are diverse and relatively stable.  Forest stability often results from the accumulation of nutrients in tree biomass.  This forms a pool (perhaps as much as 50% of the total nutrients) which are unavailable for new growth.  Under natural conditions, trees die periodically, thus opening the canopy (sunlight) and providing nutrients for young trees.  However, when a large-scale disturbance occurs, such as fire, then nutrients are released all at once and are usually washed out of the system.  Timber removal is another large-scale disturbance that reduces nutrient availability because the nutrients are removed with the trees.

Within any forest, there is a great deal of stratification (vertical zonation) that occurs in the plants, animals and abiotic conditions.  Uneven age stands (virgin) of trees typically have three strata; the overstory or canopy (over 3m high), the understory which consists of a shrub layer (0.5-3m high) and an herbaceous or ground layer (under 0.5m).  Secondary growth forests are often missing or have a reduced shrub layer because the high density of young dominant trees that shade out understory plants.  The forest floor in both communities provides habitat for numerous invertebrates, birds (grouse, partridge, quail), and mammals (rodents, foxes, deer, bear, etc.).  Soil invertebrates tend to remain underground, in the leaf litter, or under fallen debris.  The canopy plays host to a wide variety of invertebrates (often different from other strata) and birds, and, to some extent, mammals (squirrels).  The species of plants within the forest also tend to change as you move from forest interior to the forest edge.  Forest edges (stream bank or grass land) tend to have higher plant density and diversity and different species than the interior forest because more light is able to reach the forest floor.  Higher diversity is often not achieved in highly disturbed sites because invasive species often dominate the edge habitat.  Along stream banks, periodic flooding adds an additional constraint that alters the community of plant species.  Stream bank communities are often dominated by fast growing species (willow and cottonwood) that can tolerate higher soil moisture “wet feet” and periodic floods.

Central New Jersey is located at a point of transition from an oak hickory climax forest to one where sugar maple and red maple (Acer saccharum) dominate.  Oak forests have historically covered much of the Eastern United States, but because they are mostly shade intolerant, they depend on disturbances (fire, clear cutting) to allow for regeneration.  Sugar maple and ash saplings are a shade tolerant and can relatively quickly become a dominant species in a forest if no disturbances have occurred.  Once they become established, they create a closed canopy, which will shade out less saplings of shade intolerant species such as the white oak (Quercus alba).   The majority of forests in Central New Jersey were cleared early in European colonization for lumber, fuel, and farming.  Many of the forests were permanently lost to urban development, but a few small fragments were allowed to regrow and were preserved as parks or refuges.  Many of these forests would be described as secondary forests, while a few have been left long enough to develop uneven aged stand.  The current management of forests in the Eastern United States has shifted from clear cutting (good for Oaks) to selective cutting (good for maples).

Our forest ecology lab will include one day of video in a Northern NJ forest and one day of data analysis.  During part one of the lab, we will collect data on plant communities, climate, and soil conditions in the upland and bottomland forest.

This research project is attempting to answer the question of whether the upland forest has different plant and animal communities than the bottomland forest area. Your introduction and discussion should focus on these ecological principles and how they relate to our findings.

  • In which ways are upland habitats different (moisture, temperature, light etc.) than bottomland habitats? How would that impact the species in these locations? Do our findings match the theoretical community?
  • How does dominance, frequency, density and importance value help us describe the community. These will be graphed as well.


Week I:  Vegetation Analysis

We will use a method of sampling known as the point-centered quarter method (Mueller-Dombois and Ellenberg 1974) that would allow us to assess the ground, understory as well as the canopy vegetation.  We will only measure and identify canopy species.  At a sampling point, a hypothetical cross is formed which divides the surrounding area into four sections (see diagram).  In each section, plants in each category (ground, shrub, canopy) closest to the center point are measured.    First the distance to the plant is recorded, the plant is identified, and the circumference of the tree at breast height (~1 m) is measured.  We will then convert the circumference to diameter breast height (DBH).  You will be working in groups of three or four individuals and one person will record, two people will measure and the third will determine which plants are to sampled and what those plants are.  Each group will try to do as many of these “points” as possible but our goal is to measure 5 locations in both forest areas, the upland and the lowland.   Keep in mind that the first one or two goes slowly, but that things speed-up after that!


Literature Cited

Mueller-Dombois, D. and H. Ellenberg. 1974.  Aims and Methods of Vegetation Ecology.

Wiley. New York.


Smith, R. 1980.  Ecology and Field Biology.  Harper and Row Publishers.  Philadelphia, PA.


Forest community calculations:

You will analyze the interior and riparian forest communities separately and then we will compare them in the results and discussion of the paper.


  1. Calculate Alpha, Beta, and Gamma diversity (richness)
  2. Calculate Jaccard’s Index of Community Similarity
  3. Calculate forest community assessment calculations (record in tables 4 and 5)


Part 1

Alpha diversity = number of species in each site

Beta diversity = number of species that do not have site overlap

Gamma diversity = total number of species found in the sites


Part 2

Jaccard’s Index: 0 = no species in common, 2.0 = all species in common


J =

A = Alpha diversity site 1, B = Alpha diversity of site 2, and w = number of species in common


Part 3

Forest community assessment calculations


  1. Total (sum) the point to individual (tree) distances for all trees = (d)


  1. Divide (d) by the total number of individuals measured to give you the average distance ()


  1. Total density of all species = 1/()2


  1. Relative density = X100


  1. Density = X total density of all species


  1. Average dominance value = Use circumference data to calculate average area of each species


  1. Dominance = Density of a species X average dominance value for a species


  1. Relative dominance = X 100


  1. Frequency =


  1. Relative frequency = X 100


  1. Importance value = Relative density + Relative Dominance + Relative Frequency


Data Tables:

Table 1: Forest habitat observations

Observation Upland forest Bottomland forest
Temperature 53 F 52 F
Humidity 82% 82%
Percent canopy cover 80% 70%
Light level 7700 Lux 9110
Humus layer depth ½ inch none
Soil nitrogen Trace Trace
Soil phosphorus Low Low
Soil potassium High high
Soil pH 6 5


Table 2: Upland forest community of canopy layer

Site/quadrant Species common Scientific Distance (m) Circumference (m) Tree area
Site 1, quad. 1 White Pine Pinus strobus 0.73 0.32  
Site 1, quad. 2 Red Oak Quercus rubra 4.90 0.62  
Site 1, quad. 3 Red Oak Quercus rubra 2.05 0.33  
Site 1, quad. 4 White Oak Quercus alba 2.83 1.03  
Site 2, quad. 1 Mockernut Hickory Carya tomentosa 3.22 1.37  
Site 2, quad. 2 American Beech Fagus grandifola 2.25 0.21  
Site 2, quad. 3 Red Maple Acer rubrum 4.45 0.10  
Site 2, quad. 4 Sweet Birch Betula lenta 3.63 0.40  
Site 3, quad. 1 Red Maple Acer rubrum 1.88 0.31  
Site 3, quad. 2 White Oak Quercus alba 3.92 1.06  
Site 3, quad. 3 White Oak Quercus alba 2.68 0.43  
Site 3, quad. 4 White Oak Quercus alba 3.53 0.24  


Table 3: Bottomland forest community of canopy layer

Site/quadrant Species common Scientific Distance Circumference Tree area
Site 1, quad. 1 Sweet Birch Betula lenta 2.95 1.75  
Site 1, quad. 2 Red maple Acer rubrum 2.53 0.25  
Site 1, quad. 3 Red maple Acer rubrum 2.91 0.97  
Site 1, quad. 4 Red maple Acer rubrum 3.64 0.37  
Site 2, quad. 1 Sweet Birch Betula lenta 3.32 1.13  
Site 2, quad. 2 Black oak Quercus velutina 2.25 0.26  
Site 2, quad. 3 Black oak Quercus velutina 4.00 1.91  
Site 2, quad. 4 Black oak Quercus velutina 9.52 0.87  
Site 3, quad. 1 Green Ash Fraxinus pennsylvanica 4.95 1.47  
Site 3, quad. 2 Green Ash Fraxinus pennsylvanica 2.73 0.24  
Site 3, quad. 3 White Oak Quercus alba 4.05 1.43  
Site 3, quad. 4 White Oak Quercus alba 3.15 0.83  


Forest calculation are done for each tree species in a particular area (interior or edge)


Table 4: Summary of community composition measurements for upland forest


Species Density


Relative Density Dominance


Relative Dominance Frequency Relative Frequency Importance value
White Pine              
Red Oak              
White Oak              
Mockernut Hickory              
American Beech              
Red Maple              
Sweet Birch              










Table 5: Summary of community composition measurements for bottomland forest


Species Density


Relative Density Dominance


Relative Dominance Frequency Relative Frequency Importance value
Sweet Birch              
Black Oak              
Green Ash              
White Oak              
Red Maple              


Leave a Reply

Your email address will not be published. Required fields are marked *