WHY DO WE SEE WHAT WE SEE
Table 1: Different abiotic factors in each sampled area. Measured in Lower Seymour Conservation, on the 24th of December 2022, at approximately 15:00. (Sample size is 4 quadrats).
Figure 1: The species richness in each sampled area. Calculated by identifying and counting the number of unique species in each of the 4 quadrats. Sampled in Lower Seymour Conservation, on the 24th of December 2022, at approximately 15:00. (Sample size is 4 quadrats).
Figure 2: Temperature and light intensity in each sampled area. Humidity was measured to be the same in all sites, so we excluded it. Measured in Lower Seymour Conservation, on the 24th of December 2022, at approximately 15:00. (Sample size is 4 quadrats).
The open area has a slightly higher species richness (Gamma diversity = 8 compared to 6 in the forest. The quadrants sampled in the clearcut also averaged a higher alpha diversity compared to the forest quadrants). The trees in the forest are much taller and older than the trees in the open area. The abiotic conditions were warmer and brighter during the time of measurement (daytime 2-3 pm. It's likely to fluctuate more and have a lower temperature during the night due to the higher sky view factor). It was raining that day so the humidity was very high (88%) and the same for both. However we felt the clearcut to be much dryer compare to the forest on Sunny and Cloudy days before.
To our surprise, we only found one species that is invasive, and it was situated inside the forest (English holly).
Theory
Community Focus – Plant species composition. We focused on the community of plants located in two different environments, a clearcut and a forest. A community is defined as groups of different species that interact in the same place at the same time.
Species Richness – The total number of species of interest in the community.
Alpha, beta and gamma diversity – Alpha diversity counts the number of different species in a local area that shares common abiotic conditions. Gamma diversity is defined as the species richness in larger areas that includes a variety of conditions. Beta diversity is the difference in species composition between areas.
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Disturbance – A mostly abiotic occurrence that negatively affects species in a specific location. The disturbance that we are interested in is a clearcut, and it is driven by human activity. Trees and plants were removed from the landscape for the purpose of human focused functions (infrastructure, logging, agriculture and so on).
Secondary secession – Change in the composition of species following an event that reduces biotic and abiotic conditions in such a way that aspects of the previous community remain. In this case, the open area with the clearcut happened years ago is undergoing secondary secession.
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K, R selected species -
K: Species that have fewer offspring, but invest more heavily into each one, stable population growth near carrying capacity. These species take more time to reach maturity and live longer. These species thrive in competitive areas that do not face many disturbances, such as a stable forest environment (area 3 and 4).
R: Species that showcase high growth rates, so they mature and reproduce early. They can take advantage of less populated niches, produce many offspring that have low survival rates, but disperse effectively. These traits make them more efficient for succession events, and more likely to be predominant in areas that experience disturbances, such as a clearcut (area 1 and 2).
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Sky view factor – The fraction of an object's view that is occupied by another object. Objects that have a larger clear view of the sky have significantly more diurnal long-wave fluctuations, due to less objects trapping the escape of heat during the night or the incoming solar radiation during the day. Clearcuts have a much larger sky view factor in comparison to forested areas, as a result the abiotic conditions are more prone to fluctuations.
Putting it together:
​The clear-cut for the installation of power lines years ago is considered a disturbance to the current open area and is responsible for the secondary succession pattern we see. This includes. We see more biodiversity in the pen area than the forest. This is probably due to the intermediate disturbance theory that the open area had enough time to recover from the disturbance clear-cut yet has an opportunity to avoid competitive exclusion of any dominating competitive species. So both early and late successional plants thrive there. Whereas in the forest, there hasn't been any big disturbance recently so the late successional trees are growing very tall thus making sunlight less available (lower light intensity, lower temperature) for smaller early successional plants on the forest floor, giving it a lower biodiversity.
Wonder
Plants in the clearcut area were purposefully planted to be low growers to avoid interference with the powerlines above?
How long ago was the area clear-cut and powerlines constructed?
Which of the plant species is k or r selected?
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Possible shortcomings and errors to take into consideration:
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Our sample size was relatively small, with 4 areas of 3x3 meters. The conservation area is huge in comparison, so if more samples were done, the results may differ.
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Sample bias - Areas were chosen by the ease of accessibility and interest. Randomness sampling was our goal, however, we chose to situate our quadrats in areas that had a higher degree of variety. As a result, our findings may not properly represent the species richness ratio.
We only estimated to identify which species are early or late successional based on our general knowledge and field observation on the species. This could have been done more scientifically in the future.