Reudink, Post 3: Ongoing Field Observations

1.

My study will be examining the incidence of White Poplar trees (Populus alba) relative to their proximity to the perimeter of their forested area. I noticed two different environmental gradients in my observations: (i) a north-south gradient and (ii) an east-west gradient. The north-south gradient is more pronounced, as the southern zone is abundant with coniferous trees while the north zone is absent of coniferous trees and contains various deciduous species (Figure 1). Since the distribution of trees close to houses has likely been manipulated by past owners, it would be difficult to be sure that my measurements are associated with ecological differences rather than anthropological differences (e.g., conifers would be attractive to plant near one’s home as they give more coverage/privacy in the winter months). For that reason, I will focus on the east-west gradient in the deciduous zone that I have identified. I have separated the deciduous zone into three subzones: (i) east zone, (ii) central zone, and (iii) west zone (Figure 2). The downslope from east to west is less than 10°.

Figures 1 and 2

2.

Observations:

East zone: Abundant with various deciduous species that are native to Manitoba. White Poplar trees are more abundant on the north end of this zone. There were several large Manitoba Maple trees (Acer negundo L.) and Scrub Oak trees (Quercus macrocarpa Michx.). Coniferous trees were sparsely found in the southern region but decreased in abundance as I moved north, to the point of being absent at the north end. I could not reliably assess soil moisture becasue I had no equipment to do so and the snow had been melting over all of these areas over the last two days.

Central zone: Most diverse location and seemingly symmetrically distributed tree species. This zone, relative to the other zones, had a lower abundance of White Poplar that increases in abundance northwards. No conifers in the north end.

West zone: Appears to be the zone that is most abundant with White Poplars. Some conifers can be found on the south end, while none are found on the north end. The trees on the west perimeter seem to be uniformly slanted towards the west. The trees are approximately 5-10m from the adjacent dike which is currently dry. The overall

3.

There are many factors that could be contributing to this gradient. Soil composition comes to mind as a potential contributor to the incidence of tree species. Sun exposure also probably plays a role. There seems to be much greater diversity and competition in the central zone, so the White Poplars may be competing with other tree species for sunlight. I believe that sun exposure would be a better “predictor” for White Poplars than soil composition, as White Poplars are hardy trees that tolerate an array of soil conditions. Furthermore, soil composition and White Poplar concentration may have a bidirectional relationship, whereas sun exposure and White Poplar concentration likely has a unidirectional relationship. Therefore, my proposed hypothesis is as follows.

Hypothesis: Sun exposure influences the incidence of White Poplar trees.

Prediction: The incidence of White Poplar trees will be greatest in locations of high sun exposure, like the east and west perimeters.

4.

Predictor (explanatory) variable: Duration of sun exposure (continuous)

Response (outcome) variable: Incidence of White Poplar trees (continuous)

A regression analysis would be sufficient for an experimental design (statistical analysis), as both variables are continuous.