The effects of Canopy Cover on Herbaceous Vegetation Robbie Rettig, 2018, ppt, Key words: Canopy cover, herbaceous vegetation, Ponderosa Pine Robbie Rettig – Summer 7/22/2018 Vegetation Ecology EBIO 4100 Course location: Mountain Research Station, University of Colorado, Boulder

Introduction Canopy cover is the layers of leaves, branches, and the stems of trees that cover the ground below (Korhonen, 2006) Commonly expressed as a percentage of total ground area Adversely affect the growth of herbaceous plants beneath them (Jennings, 1999) (Abrams, 1988) Competition for light, water, and nutrients Very little sunlight and precipitation can penetrate beneath thick canopy cover (Jameson, 1967) Canopy cover can be defined as the layers of leaves, branches and the stems of trees that cover the ground below, usually expressed as a percentage of total ground area. Canopy cover adversely affects the growth of herbaceous plants beneath them through competition for light, water and other nutrients. With very little sunlight and precipitation able to penetrate beneath thick canopy cover, herbaceous vegetation beneath it isn’t able to flourish.

Question Does the percentage of canopy cover affect the resulting herbaceous vegetation beneath it? My question is if the percentage of canopy cover affects the herbaceous vegetation beneath it. Is there a correlation between High and Low canopy cover and the resulting herbaceous vegetation?

Hypothesis Null: There is no observable difference in canopy cover percentage and the resulting herbaceous vegetation. Alternative: There is an observable difference in canopy cover percentage and the resulting herbaceous vegetation. Null: There is no observable difference in canopy cover percentage and their resulting herbaceous vegetation. Alternative:

Methods Sampling of 3 Sites (6 Areas) - Locations: Table Mesa (high canopy, low canopy) Chautauqua (high canopy, low canopy) Betasso Preserve (high canopy, low canopy) *Canopy coverage was only taken below Ponderosa Pine Trees to have consistent tree coverage For my methods, I started with 3 sites, one at Table Mesa, one at Chautauqua, and one at the Betasso Preserve. At each site, two areas were selected, one having high canopy cover and the other low canopy cover. A 25m transect was laid down at each at each area, where a random number generator was used to select 6 random points, giving us a total of 36 data sets, 18 for both High and Low canopy coverage. Canopy coverage was also only taken below Ponderosa Pine Trees to have consistent tree coverage My image.

Methods con. Canopy Cover CanopyApp iPhone application that measures canopy cover (%) 6 data sets were taken at each area, 36 total Herbaceous Vegetation Point-frame Method Used to measure herbaceous vegetation % cover For testing my different points, I used an application called CanopyApp that is used to measure the canopy density above. Before using the app, I ran testing runs with the canopy mirror to determine accurate readings. CanopyApp was very accurate compared to the mirrors readings. To test for herbaceous vegetation beneath the canopy cover, I used the point-frame method to determine the % of the ground covered by herbaceous vegetation. 6 data sets were taken at each area for both methods listed above, giving me 36 total points for each method. 12 for each site. My images/CanopyApp logo

Results – Linear Regression P<0.001 Running a linear regression, I found that canopy cover significantly affects the herbaceous vegetation beneath it, having a p value of less than 0.001. From the graph, you can see that as the percentage of canopy cover increases, the percentage of herbaceous vegetation beneath it decreases, and visa versa, creating this significant relationship between both variables. The highest point in canopy coverage, 90%, also has the lowest herbaceous vegetation coverage, 27.7%. Polynomial treadline R^2: 0.879 Linear treadline R^2: 0.860 P<0.001

Results – Two Way ANOVA P<0.001 P<0.001 I also ran a two way ANOVA to compare my 3 different site’s canopy cover at Table Mesa, Chautauqua, and the Betasso Preserve. All three of my sites had a p-value of less than 0.001, meaning that there’s a less chance of the differences being a coincidence at the different locations. In the graph, we can see the averages of of high and low canopy cover are very similar across all sites except the Betasso Preserve, averaging a low canopy cover of 40.55% and a high canopy cover of 70% while Table Mesa and Chautauqua have low canopy cover’s of 53% and high canopy cover’s of 75%.

Results Summary Linear Regression: - p-value < 0.001 - R^2: 0.86 ANOVA: - Table Mesa p-value < 0.001 - Chautauqua p-value < 0.001 - Betasso Preserve p-value <0.001 I found that canopy cover significantly affects the herbaceous vegetation beneath through my regression analysis. The p-value was less than 0.001 and my R^2 was 0.86, meaning data is close to the regression line. All three of my sites had a p-value of less than 0.001, meaning that there’s a less chance of the differences being a coincidence at the different locations.

Discussion Canopy Cover adversely affects the herbaceous vegetation beneath it Competition through resources Herbaceous Vegetation greater with lower canopy cover More sunlight Water Availability From our data, we saw that canopy cover (%) affects the resulting herbaceous vegetation beneath it. This was true at all sites, Table Mesa, Chautauqua, and the Betasso preserve. With limited canopy cover, the vegetation beneath is able to better obtain sunlight, water, and nutrients. High canopy cover can prevent this through competition, as the canopy cover obtains most of the sunlight and precipitation.

Further Research What other factors along with canopy cover affect herbaceous vegetation? Elevation, animals, climate Betasso Preserve Canopy Cover Why does Betasso Preserve have less canopy Cover? Soil composition, rainfall, other trees Further research that could be done is to look at what other contributing factors might affect herbaceous vegetation like canopy cover, such as elevation, animals, or climate. Looking at my data, the Betasso preserve seems to have both a lower Low canopy average and a lower High canopy average. Further research could be done to explain this, with soil composition, rainfall, or competition with other trees being possible factors.

Conclusion High canopy cover results in lower herbaceous vegetation under Ponderosa pines trees Similar results across Table Mesa, Chautauqua, and Betasso Preserve Herbaceous growth significantly higher with lower canopy coverage Canopy coverage correlates with herbaceous vegetation coverage In conclusion, I found that canopy cover significantly affects the herbaceous vegetation beneath it, being that high canopy coverage results in a lower herbaceous vegetation cover and lower canopy coverage results in a higher herbaceous vegetation cover. All 3 of my sites provided the same conclusion about canopy cover and its affect on herbaceous vegetation.

References Abrams, M. Effects of Burning Regime on Buried Seed Banks and Canopy Coverage in a Kansas Tallgrass Prairie. The Southwestern Naturalist. 33 (1) 65-70 (1988) Jamesone, D. The Relationship of Tree Overstory and Herbaceous Understory Vegetation. Journal of Range Management. 20 (4) 247-249 (1967) Jennings SB, Brown D. Sheli D, Assessing forest canopies and understory illumination: canopy closure, canopy cover and other measures. Forestry: An International Journal of Forest Research. 72 (1) 59–74, (1999) Korhonen, L. Estimation of Forest Canopy Cover: a Comparison of Field Measurement Techniques. The Finnish Society of Forest Science. 40 (4): 577–588, (2006) Strickler, G. Use of the densiometer to estimate density of forest canopy on permanent sample plots. PNW Old Series Research. 180 (1) 1-5, (1959)