Lab Exercise I: Community description in the river valley
This lab was designed by M. Coupe, M. Simpson, and J. Cahill.
Goals
Become familiar with common analytical methods used to describe plant communities
Investigate how changes in nonvascular plant community structure are associated with small-scale differences in habitat.
Background
As much as plants are often overlooked in conservation programs and the media at large, nonvascular plants are generally treated even worse. We can think of numerous newspaper photos of agricultural crops, roses, and other “useful” plants, though how often have we seen photos of lichens and mosses in the popular press? Despite the fact that people generally ignore them, nonvascular plants exist in most every community and can be a substantial part of the diversity and production in many communities (bogs, fens, boreal forest, etc.). For most communities we have very little idea exactly which species are found where, let alone any idea as to how these organisms influence the overall structure and function of a given community. This is in part due to the relative complexity of identification of these small organisms, and in part due to the fact than many bryologists/lichenologists come from a taxonomic rather than ecological training. The first step in most studies in community ecology is to document the distribution and abundance of the species present. From this information one can develop and/or test theory about the mechanisms which generated those distributions.
Lichens and bryophytes are diverse components of the communities of Edmonton’s River Valley Park, and are among the smallest members of plant communities. Lichen colonies can grow extremely slowly, as little as 5 cm per century. The final size of a lichen colony is often dictated by the point in time that their host substrate dies or suffers a severe physical disturbance, though some species growth is also strongly influenced by air quality. Nonvascular plants live on a variety of surfaces that all tend to have long-term stability, and rocks and bark are common suitable habitats for many species. Surfaces with more diverse colonies have often existed, or been undisturbed, for a longer time, and one can identify predictable patterns of succession among the non-vascular flora.
Though many “vascular” plant ecologists lump all nonvascular plants together when measuring biomass and area, each species of non-vascular plant can in fact be very different from the others – each with its own unique niche. As a result, one is likely to find different species occupying different host plants and/or areas with differing micro-meteorological regimes. Like all plants, non-vascular plants have a range of tolerance to light and temperature that varies among species. Also, different species have different forms of interactions with the host substrate, and thus one species of host tree may not support the same non-vascular species as another species of host tree.
Populus balsamifera and Populus tremuloides are two fast growing tree species, common in the Edmonton River Valley. Within the forest, there are a range of light and temperature conditions than can vary as a function of location on the tree (high, low, north facing, south facing), and as a function of the location of the tree (in a gap, in dense vegetation, along a path). As a result, this setting is an ideal choice for a study designed to describe how non-vascular plant communities vary along with small changes in the local environment.
Lab Objective: Record the presence of all non-vascular plant species found on 3 P. balsamifera and 3 P. tremuloides trees. Subdivide the tree into low and high sections on both the north and south side of the tree. In total, you and your partner will record the presence of all non-vascular species in 4 sections in each of 6 trees. Use this data, along with the data collected by the rest of the class as well as a variety of environmental measures, to determine what factors are important in structuring non-vascular plant communities.
A picture key of the common non-vascular plants in the river valley can be found here.
Equipment
String, flagging tape, pen/pencil, sharpies, pin flags, wax pencils, compass, hand lens, plant id guides, DBH tapes, micro-climatic measuring equipment.
Lab Protocol
Learn to reliably identify both Balsam Poplar (Populus balsamifera) and Trembling Aspen (Populus tremuloides).
Balsam poplar has sticky buds that are fragrant with resin. Aspen does not.
The old bark of Balsam polar is dark and deeply furrowed. Aspen's old bark becomes black and rough on lower trunk and around branch bases. Young bark of Aspen is greenish white.
Balsam poplar has egg to lance shaped leaves, Aspen has oval to nearly circular leaves.
Balsam poplar has a round petiole, Aspen has a flattened petiole.
Become familiar with the more common non-vascular plant species found on and around these two tree species.
Use the picture key and the available texts to aid in species identification.
Talk you your TA and the other groups around you when you find unknown specimens.
It is very important that all groups call the same species by the same name. It is less important that we call each species by its actual name.
Ask your TA for the data sheets you are to use. At this time, the TA will make sure your group can reliably identify the species you are likely to find during the lab exercise.
Randomly select a tree.
Use only trees that are more than 15 cm DBH (diameter at breast height).
Use only trees you can positively identify to species. Ask you TA is you are unsure..
Be sure that no other group in the class has selected the same tree.
Layout four 10 cm (horizontal) x 50 cm (vertical) quadrats on the tree. Use flagging tape, string, and pin flags to assist you in marking out these four rectangles. The quadrats should be located as follows:
North facing, ground level to 50 cm high.
South facing, ground level to 50 cm high.
North facing, 100 to 150 cm high..
South facing, 100 to 150 cm high.
Record light levels and temperature at each of the four sections. Categorize each section of the tree as: wet, moist, or dry. Measure the diameter of the tree at the midpoint in each of your two heights.
Record the presence and approximate area covered by each nonvascular species located within each quadrat.
Do not record those growing on the soil near the tree, or on the tree outside of the quadrat.
Area should be recorded as a % of the tree bark covered by that particular species, rather than absolute size. If two species are growing on top of each other, the total % of cover can exceed 100%.
After all species have been recorded, go back to step #3, until 6 trees have been measured, or time has expired.
A few pointers:
As time may expire before you can measure 6 trees, only mark one tree at a time.
Alternate between the two species, such that when time expires, you will have approximately an equal number of samples of the two tree species.
Leave a pin flag in the ground next to each tree you use. This will help ensure other groups in the class do not use the same tree. Be sure to retrieve all the pin flags at the end of the lab.
Assignment
At the end of the lab, give your TA your group's data sheets. The TA will compile all of the data from the class.
Later in the term, you will be given the assignment of analyzing and interpreting this data. This assignment will include basic analyses of community properties (e.g. species richness, diversity, etc.), as well as more complex analyses of community structure (e.g. ordination).
Details of the assignment will be provided following the lab lectures on statistical analyses and ordinations.
Other than the data sheets themselves, there is nothing for you to hand in at this time.