On March 19, 2022, I collected my initial data for the research project. While I very much enjoyed collecting data on the south-facing slopes, I encountered a few challenges on the North-facing slopes:
- Portions of the North-facing slopes were extremely dense and basically impossible to go into to collect data
- Accurately collecting % cover data on the North-facing slopes was challenging and I do not feel as though my collected cover data provides an accurate representation.
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- While shrubs were still present on the North-facing slopes, they were more like twigs/sticks sticking out of the ground, not full shrubs with multiple stems/trunks.
- To not include trees in my data collection, could appear as though the North-facing slopes were sparsely vegetated.
- I collected two values of cover data for the North-facing slopes, one just for the shrubs and another that included the tree canopy.
While I encountered issues on the North-facing slopes, I do feel that one of my predictions appears to be holding true, and that is that shrub coverage will be greater on the south-facing slope – so far.
A major challenge I will encounter no matter what method I use is how to evaluate the extremely shrub-dense portion of the north-facing slope. If I continue with my same sampling method of running a transect every 10m, then I will encounter some areas of such thick shrub density that I will not be able to enter the area (and I’m still unsure how to proceed here).
I keep going back to the Module 3 tutorial to evaluate if there would be a better way to estimate cover, but I keep coming back to the same method. It is challenging to use the same sampling method between the 2 slopes and get comparable results. That is, I used a 4m diameter circle as the area to collect my data at each sub-unit along my transect. On the south-facing slope all the vegetation was below hip height, so I could easily stick my hiking pole into the ground at the centre of my plot, hang onto my 2m long rope that was attached to the hiking pole and walk in a circle around the plot and identify all the shrubs within that plot. Then I could stand back and identify the approximate cover. However, on the north-facing slopes, there were multiple trees in the way that made the circle very difficult to identify and the cover challenging to estimate.
After a discussion with Nancy, she has suggested that perhaps I have chosen too many attributes to study and that I should narrow in on one subject, which is why I would like to go back to a study closer to my original topic – vegetative structure and how it changes between aspects. We also discussed that the changes I’m noticing are plant community structures and how they change and vary depending on slope aspect.
I plan to change my sampling method too – I will be using the point-intercept method to study plant community structural classes (understory vs. overstory). Each transect will be 30m in length and will run up and down the slope (so parallel with the slope). Then at every 1m mark, using a pin, I plan to record the structural layers (grass, forb, shrub, tree, and maybe Lichen/Moss). I am going to stick to the vegetation type opposed to the vegetation species as I’m more interested in the plant community structure than I am the diversity. I will specifically record the “top-canopy” vegetation then also the lower layers. This way I can use the data to evaluate the plant community structure as well as potentially find patterns in the dominant “top-canopy” vegetation type.
To make things extra clear (I hope…) – I am adjusting my hypothesis and variables as follows:
Hypothesis: Slope aspect influences plant community structure.
Predictions:
- North-facing slopes will have more structural layers than the south-facing slope
- South-facing slopes will contain less overstory plants but its total vegetative cover will still be equivalent to the north-facing slopes.
Response Variable:
- Plant community structure; Categorical because it will be either classified as overstory or understory.
- Vegetative/ground cover; Continuous because it will be measured on a continuous numerical scale (% cover).
Explanatory Variable: Slope aspect; Categorical because it will be either north-facing or south-facing slope.
This is where I am learning the point-intercept method using a multilayer technique: https://www.webpages.uidaho.edu/veg_measure/Modules/Lessons/Module%208(Cover)/8_3_Points.htm
Hello
yes not being able to enter an area is challenging. At some point you need to get eyes on.
so with your new hypothesis and predictions, remember that cover can be greater than 100% – a shrub canopy over a grass for example could equal more than 100% if shrub = 80% and grass/forbs etc making up understorey = 60% (more than 100% in total)
interesting because often I find south facing slopes to have greater diversity in terms of overstorey/understorey – north facing slopes can be dominated by large trees with little understorey, but it certainly sounds like your site has shrubs on the north side
ok the point intercept method is pretty labour intensive – just a note – if you use two tripods and pins – I kept scrolling down and see the pacing method along a transect. there is a lot of info on the page for sure and keeping it simple is probably the best, given access issues
hope this helps