Within ecology, there is a process that can be seen within a community that deals with the replacement. This process is known as succession. Another defines it as “the progressive, orderly, and somewhat predictable series of replacements of one community by another,” (5d, n.d.). During the process of succession, many changes occur within the community as a whole. Obviously, the composition of the community is changing, as the definition would imply, but the life forms and even the habits must change in order to adapt to the new composition of the material. Additionally, one can expect to see a boosted quantity of biomass as succession occurs, as well as an increase in both productivity and the development of more complex community structures. One of the environmental changes that go along with the notion of succession is the soil chemistry. Succession can be further divided into two major categories: primary and secondary. Primary succession is defined as “beginning on sterile substrate,” whereas secondary succession “begins on substrate that previously supported life (e.g., flooded, burned, grazed, logged, or farmed areas),” (5d, n.d.). In our experiment, we are mostly focused on secondary succession.
For this experiment, it is also necessary to understand the difference between species diversity, specifically the difference between the ideas of richness and evenness. The Encyclopedia of Earth defines species richness as “the number of species present in a sample, community, or taxonomic group,” (McGinley, 2010), and it defines evenness as the measure of “the variation in the relative abundance of individuals per species within a community,” (McGinley, 2008). Knowing this, our experiment puts forth two main hypotheses: a null and an alternative. The two hypotheses are: (1) mean species depthless and (2) mean species richness. What we were attempting to measure was how things change with second-degree succession by measuring and testing the NOVA by looking at the depth change.
Before the method of the experiment can be described, it is important to understand the idea of what a sere is within ecological succession and what the four seral stages are. The biology online dictionary defines seral stages as, “the series of relatively transitory plant communities that develop during ecological succession from bare ground to climax stage,” (Biology Online, 2005). Within the seral stages, there are typically seen to be several subcategories. The early stages of a seral all deal with pioneer species being introduced to a relatively harsh, extreme environment that gradually gains more organic biomass as the pioneer species can provide organic components and optimal germination to the soil of the area. Then, more diverse species of organisms can begin to settle in the area, as it has been, in a sense, treated and made possible for more species to flourish there because of the pioneer species. After a period of time, a climax stage is reached where the largest possible amount of species will occupy the area under observation, and the highest amount of diversity can be expected to be observed. It is important to note that, “although the word ‘stage’ implies a simple linear sequence, contemporary ecological theory does not view succession as a predictable process where distinct assemblages of vegetation replace one another at each stage until an obvious endpoint is reached,” (Yearsley & Parminter, 2000). One must realize that succession must be viewed as cyclical, in that it is a continuous process where stages are likely to overlap one another.
For the experiment, it was necessary to look at the soil data that was collected. Some of the factors considered were litter depth and horizon measurements (depth, color, texture). The litter depth was 10 spots measured in ruler centimeters. In regard to the horizon measurements, the soil pitch was 20 inches in depth with a color measured by chroma/value and a soil texture measured by the rapid method flow chart. The experiment identified 24 species ranging from tree, sapling, shrub, woody vine, and herbs. We looked at the vegetation in a 21-meter diameter during the experiment. The calculations of the experiment were to find the H’ calculation, measure the ANOVA with regards to the mean species richness and mean litter depth, calculate the SPSS, and calculate the alpha value. If the ANOVA were significant, we would run a post HOC test on the data collected.
The soil analysis found the following. Within the seral stages, all had horizons O, A, and B present, and they in thickness between 1.5-2.5 cm for horizon O, 8-18 cm for horizon A, and 21-35 cm for horizon B. The Old Field (OF) Seral Stage additional had a horizon E with a soil thickness measurement of 19 cm. All of the stages had equal ratios of chroma/value for horizon O. The OF seral stage data followed as horizon A receiving 4/4 for the Chroma Value with a Loam texture, horizon E receiving 5/6 for the chroma/value with Silt Loam texture, and horizon B receiving 5/8 for a chroma/value with a Silt Clay Loam texture. The Mid-Transitional (MT) seral stage received 4/6 for a chroma/value with a Sandy clay texture for horizon A and a 6/8 chroma/value with a Silty Clay texture for horizon B. The Late Mixed Transitional (LT) seral stage received a 5/8 chroma/value with Sand Clay Loam texture for horizon A and a 3/3 chroma/value with Sand Clay Loam texture for horizon B. Finally, the Old Field (CC) seral stage received a 4/6 chroma/value with Silty Clay Loam texture for horizon A and a 5/6 chroma/value with a Clay Loam texture for horizon B. There were a grand plant total of 1984, 8144, and 863 observed plants in Quadrants 1, 2, and 3 respectively, and a grand total of 8, 12, and 8 different types of species observed within quadrants 1, 2, and 3 recorded.
The way in which the soil was classified was subject to testing from the experimenter. Approximately 15 grams of dry soil was placed in the palm of the hand of the experimenter and had a series of tests conducted upon it to see its classification. The extensive tests, including such as defining the composition, texture, plasticity, molding capacity, etc. were used to determine what type of soil was present. The potential types of soil were as follows: sand, loamy sand, sandy loam, silty clay loam, silt loam, loam, sandy clay, sandy clay loam, clay loam, silty clay, and clay. The method used for determining the soil texture and type were found in fig. 3-3 entitled “Rapid method for estimating soil texture.”
Soil texture is quite important to understanding and recognizing what a land area can support in terms of vegetation. It is not only important in a natural setting such as with the experiment, but it can be of the utmost importance to the agricultural field in that the soil texture can determine important information about what sort of crops can grow. Some of the most important factors about soil texture deal with the following: “drainage, water holding capacity, aeration, susceptible to erosion, organic matter content, cation exchange capacity (CEC), pH buffering capacity, and soil tilth,” (“Agronomy fact sheet series”, 2007).
One of the other major areas of discussion for this experiment is the succession specifically of the soil and the effect that it has on the type of vegetation that can be supported within a certain area. It is important to realize that as an area has a succession of soil, the fundamental composition of the vegetation in that area will begin to shift, which can speed the process of the change of the soil composition and the overall succession of that area. For example, in Michigan, the forest type will “influence soil development, erosion potential, soil pH, organic matter volume, water retention, water quality, and similar forest characteristics,” (Cook, n.d.). The change in soil composition during the gradual shift of soil composition will directly affect the types of vegetation and even animals present in the environment as they are all “in their habit strategy” which maximizes their chances of both survival and successful reproduction.
It is also important to understand the cyclical nature of succession as it relates to botany. Naturally, the cycle ends by itself in a “stabilized community and ecosystem called the ecological climax,” where it is “in equilibrium with the physical environment of that particular are and perpetuates itself,” (Winstead, n.d.). However, because the outside world has an impact on the nature of the environment, there are factors that can send the succession back to its earlier stages. An external disturbance to the area such as fire will destroy the vegetation and resort the area back to the harsher, earlier stages of the succession cycle. Though this would seem detrimental to the area, it is actually a necessary and important phase of succession as it removes the older, larger species from the area and gives a chance for the younger generations of vegetation to gain a foothold and prosper in that environment. It is also important for the area that experienced outside disturbance to experience a period of rest. Rest, in general, is one of the key areas that are responsible for succession to be able to progress forward and is very important for the larger and more complex stages of succession to be reached. For example, large prairie environments are well suited for providing grazing grounds for animals, however appropriate rest is needed for that area to maintain its own productivity so that it is not exhausted and cannot support the vegetation thusly reverting back to an earlier, less supporting succession stage (Porter, 2009).
Finally, it is worth noting that the analysis of soil can show interesting factors about the history of the composition of the area observed. One can see the previous failures of the soil structure of the area by examining the soil profile. By estimating their age, one can see the overlap of the life periods of the soil profile of the area and make inferences as to why one particular soil profile was successful in that area while the other was not. This also shows that the difference in the development rate of these different soil profiles perpetuates the idea of heterochronism within the soil. The difference in soil evolution will have a distinct impact on the vegetation that can be supported in the area as well as the rest of the environment as a whole. This shows that “it is apparent that the analysis of soil succession of different ages and similar origin provides an opportunity to estimate simultaneously the spatial and time components of soil heterogeneity,” (Basevich, 2010).
5d. (n.d.). Ecological succession. Analysis of Communities, 194-197.
Agronomy fact sheet series: Soil texture. (2007). Informally published manuscript, Department of Crop and Soil Sciences, Cornell University, Retrieved from http://water.rutgers.edu/Rain_Gardens/factsheet29.pdf
Basevich, V. F. (2010). Soil succession and their connection with the heterogeneity of podsolic soils. Moscow University Soil Science Bulletin, 66(3), 118-122. doi: 10.3103/S0147687411030021
Biology online. (2005, October 03). Seral stages. Biology Online Dictionary, Retrieved from http://www.biology-online.org/dictionary/Seral_stages
Cook, A. B. D. (n.d.). Succession and forest change. Unpublished manuscript, Michigan State University Extension, Michigan State Univesity, Retrieved from http://mff.dsisd.net/Environment/Succession.htm
McGinley, M. (2010, April 27). Ecology theory: Species richness. The Encyclopedia of Earth, Retrieved from http://www.eoearth.org/article/Species_richness?topic=58074
McGinley, M. (2008, July 22). Species diversity. The Encyclopedia of Earth, Retrieved from http://www.eoearth.org/article/Species_diversity
Porter, M. (2009, Aug). Succession in plant communities and soil. The Samuel Roberts Noble Foundation. Retrieved from http://www.noble.org/ag/wildlife/plantcommunities/
Winstead, R. (n.d.). Ecological succession. Unpublished manuscript, IUP Biology, IUP, Retrieved from http://nsm1.nsm.iup.edu/rwinstea/succession.shtm
Yearsley, K., & Parminter, J. (2000). Seral stages across forested landscapes: Relationships to biodiversity. British Columbia Ministry of Forests Research Program. Retrieved from http://www.for.gov.bc.ca/hfd/pubs/docs/en/en18.pdf