User: | Open Learning Faculty Member:
I collected 61 replicates over the three stratified zones. Points were randomly generated using the “Random Points in Polygon” feature in QGIS. First, I determined the area of each of my zones using QGIS. They were as follows:
Alder Zone (zone 1): 7895m2
Grand fir/ Douglas-fir Zone (zone 2): 24239m2
Arbutus/ Garry oak Zone (zone 3): 10932m2
Based on the proportion of the total area that each zone represented, I divided up the 60 replicates to attain the following sampling intensity:
Zone 1: 12 (rounded up from 11.5)
Zone 2: 34
Zone 3: 15
I exported the random points as a GPX file and loaded them onto my GPS. In practice, the sampling strategy worked fairly well. It was difficult to reach some areas due to shrubby undergrowth, but since the areas which were dominated by shrubs lacked H. helix, I was able to visually assess these quadrats. A number of my points landed directly on the trunks of trees, and one landed on a well worn path. For these points, I shifted the sampling over by 2m to the north.
I noticed in my sampling that zone 3 is not entirely contiguous, with some small patches of Douglas-fir dominant stands. Overall, only two points landed in one of these patches, and these data points were not dissimilar from other replicates in the same zone. Since Douglas-fir is able to cope with some level of water stress, I don’t think this is compelling evidence against my stratification. Visually and by touch, the soil is drier in this area, regardless of the presence of arbutus and garry oak.
