User: | Open Learning Faculty Member:
I used systematic sampling across each of my three cross-sections to study soil moisture, using a 7inch probe, along the slope of my chosen area. At each interval I’d measure one soil moisture reading, the percent slope using a level and ruler, and the presence/absence of trees in a 2m2 radius.
There were a number of key issues I ran into throughout this process. The process of systematically sampling horizontally across the slope and taking only one reading at each stop did not always render replicates with similar slopes for comparison. In order to address this issue moving forward, I may have to modify my design to include taking more than one percent slope and soil moisture reading within each quadrant to ensure replicates and/or set pre-determined ranges for what constitutes a mild, moderate and severe percent slope for clarity purposes. The second issue I ran into was using my equipment in a consistent manner. Initially I would insert the soil moisture probe to its maximum depth, but ran into issues in later sampling when this was not possible due to soil conditions. To ensure the accuracy of my results in future sampling, I need to improve the consistency from which depth I take my soil moisture readings. I can accomplish this by either taking moisture readings at various depths at each point or marking an insertion limit on the probe itself at some point <7inches to ensure that it’ll be consistently inserted to the same depth. Other general modifications to future sampling will include expanding the size of my quadrants to improve data collection regarding tree sampling, and to gather more detailed information regarding the observed trees in order to better understand the potential impact of soil moisture, as it pertains to slope, on their growth. I will continue to implement systematic sampling; however, it will obviously need to be adapted to account for the larger quadrant sizes. I will also look into whether there is a way to accurately, and more efficiently measure percent slope since using a level and ruler was a tedious, and time-consuming process that will only become more challenging with more sample points.
The results were surprising to me in that they were not aligned with my prediction. I predicted soil moisture would be highest at the bottom of the slope, and what I found during this preliminary research was that it was highest at the midpoint. I have some ideas about why this might be, but evidently, I will have to wait until I’ve collected more data to comment on the findings with any reliability.
You’ve clearly given a lot of thought to your initial sampling and how it can be improved. I like all your ideas. I think there is an app for slope steepness that you could look into.