Canopy Vegetation Monitoring Project

Megan Gaitan and Brian McIsaac

The Copeland Creek Monitoring Plan has grown from an ecological model formed at the start of the semester into a full blown project that now includes a baseline level of data and clearly outlined methods for monitoring in years to come. This investigation stems from eight attributes our class identified as the most important qualities we value in the creek: hydrology/channel morphology, native understory plant community, native canopy, aquatic community, avian community, the western pond turtle, steelhead, and wide-ranging/apex species.

With our love of plants and passions for biodiversity, our pair was tasked with creating objectives aimed at restoring the native canopy of the creek. The first one we formed was aimed at removing those willows (Salix spp.) that posed the largest threat to flooding the surrounding neighborhoods and replacing those trees with Alders and Cottonwoods. With data already having been collected form previous years on the willows, our group chose to focus on our second objective. This goal was targeted at improving the structure and composition of the canopy layer in order to provide more suitable wildlife habitat and more shade to cool water temperatures in the creek. With so many trees residing on the banks of the creek we were excited to get our hands dirty and learn about what’s going on in treetops.

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Photo by C. Christian

As we’ve learned this semester, baseline data is key in measuring the success of restoration. You have to know where you want to go but you also need to remember where you started. And so, we identified three indicators that would help us and future classes assess progress. We determined canopy cover, density, and composition were the ways to gauge success. We evaluated the first indicator with a tool called a densiometer. This tool is as simple as it gets. It’s a hinged wooden box that opens up to reveal a convex reflective lens that is used to estimate overhead cover. Density and composition used species present in the creek and their diameters at breast height (DBH) to obtain information on the canopy’s structure that will determine where plantings of native tree species can be made that will improve weaker areas of the creek.

We couldn’t wait to get out on the creek and investigate current conditions of the canopy. Looking at riparian research methods in published journals allowed us to get an idea of how to design our sampling protocol in order to obtain substantial data. Along the four zones of the creek were six predetermined locations on the south bank where we would be collecting data. We marked these points and set up our transect facing north. Densiometer readings were taken at 3 m intervals beginning at 0 and ending at the edge of the bank. Each reading consisted of counts made in four directions: N, S, E, and W. Beginning again at the 0 m mark, we walked along the reel with a meter stick and recorded species names of trees whose bases fell within range of 1 m to the left and 1 m to the right of the line. Diameter at breast height was recorded for these species. If the diameter was less than 1, it was recorded as a sapling. Overhanging branches of trees whose bases were outside the range of the transect were ignored. This process was repeated at each of the six locations.

Data obtained from our bit of fieldwork was entered into Excel for calculations and graphing. Three figures were produced: percent shade at each transect, average diameter at breast height at each transect, and a scatter plot of average diameter at breast height against percent shade. Our results were not as informative as we hoped and they did not capture a full representation of the canopy or its structure and composition along the entire length of the creek. Much of the shade accounted for in the densiometer calculations of percent shade comes from the surrounding trees whose bases fell outside the range of the transect lines and shade levels of deciduous trees were not taken into account. Also, very few trees were encountered along the six transects. These factors make it difficult to understand what’s fully going on in the canopy. In the future, having a larger sample size will allow for a better understanding as well as collecting data from the opposing bank.

Despite challenges of not securing enough data to have more informative results, there were plenty of positive outcomes for our group. Together, we gained experience in experimental design, we learned how to practice various sampling techniques and data collection methods in the field, we learned how to quantify responses of canopy cover, species richness and composition, we have suggestions that can improve upon this protocol, and most importantly we learned firsthand how the restoration process is done. This set of skills we’ve developed through working with the campus on Copeland Creek is incredible. The challenges we faced in accomplishing this project will allow future classes to make great strides in successful restoration of the creek.

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