Study Date / Time : Oct 1, 2017 from 3:00 to 5:00 pm
Weather: Overcast with warm temperatures (±19○C)
I plan on studying the spatial distribution of invasive species within the ecological reserve, particularly along well delineated and abrupt edges with residential development. The environmental gradients I have chosen are distance from the reserves edges to residential development and soil development (thickness and moisture regime) relative to the Coastal Douglas fir and Garry oak ecosystems.
During this field assessment I focused on assessing the south boundary, where the topography ranges from wide, gentle benches separated by bedrock hummocky terrain. “True” Garry oak zones appear to only occur on the bedrock hummocks, where soil thicknesses are generally less than or equal to 0.2m and are rapidly to very well drained. Although, it should be noted that some areas within the Garry oak ecosystems are actively being succeeded by Douglas fir. The Douglas fir stands are found mostly on wide, gentle benches at lower elevations. These benches are mostly covered in a veneer (≤1.0m) of rubble and silt colluvium underlying a variably thin(≤0.3m) layer of organics. In the southwest area of the reserve pockets of loose, sand marine deposits were found to underlie the aforementioned colluvium , cumulatively up to 1.5m thick. In appears that the Douglas fir stands favour sites with thicker soils that are mostly well drained. Some small local areas with moderately well to imperfect drainage are also found on these benches.
While I have observed numerous invasive species so far during my field observations and past excursions I plan on narrowing the number species down to a select few. These include the most prevalent species: Cirsium arvense (Canada thistle), Daphne laureola (spurge laurel), Senecio jacobaea (tansy ragwort) and Ilex aquifium (English holly). It is currently early fall and some of the herbaceous plants are beginning to die off. This may lead to errors in further assessments. For this reason, I likely will exclude Canada thistle and tansy ragwort from my studies.
During this field assessment I made some rough estimates of densities and / or cover class by percent for English holly and spurge laurel. Based on these observations there are notable differences in the distribution and abundance of invasive species between the two ecosystems immediately along the south edge adjacent to residential development. Invasive species appear to have more successfully colonized the Douglas fir ecosystems, specifically on benches and depressions with thicker soils. As well, there is a correlation between increased light availability due to gaps in forest canopy and the higher frequencies of invasive species. In contrast, the Garry oak ecosystems have an abundance of light availability but appear to have less invasive species. It is thought that this is due to these areas having thinner soils with drier moisture regimes in comparison to the Douglas fir stands.
Hypothesis: The presence and abundance of invasive species in the ecological reserve is influenced by close proximity to the forest edges adjacent to residential development and the Douglar fir and Garry oak ecosystems.
My null hypothesis is that the distance from residential development and the two dominant ecosystems have no effect on the spatial distribution of the invasive species.
Response variable: Presence and abundance of English holly and spurge laurel.
Predictor variable: Distance from edges adjacent to residential development ; soil thickness and moisture regimes.
Figure 1. Garry oak ecosystem with ~≤1.0% invasive species
Figure 2. Garry oak ecosystem adjacent to development
Figure 3. Daphne laureola seedling
Figure 4. Field Notes
