1. Canopy cover’s effect on herbaceous ground vegetation
Stephanie Allen 7/22/2015
Vegetation Ecology Ebio 4100
Stephanie Allen July 2015 Canopy Cover’s Effect on Herbaceous Ground Vegetation Keywords: canopy cover, herbaceous ground vegetation, litter accumulation, canopy densities

2. Introduction
-Tree canopy cover can act as a competitor with ground vegetation (Laurent, 2003)
-three factors that contribute to undergrowth abundance (Harrington, 1999) (Werner, 2003)
-sunlight penetration
-water availability
-litter amount
-large amount of rainfall this year (~19 in so far) should increase water availability for undergrowth for all locations
-increase chance for vegetation
Tree canopy cover can act as a competitor for resources with other species especially herbaceous ground vegetation. This vegetation requires 3 main things to flourish they are sunlight, water, and nutrients. Their nutrients come from the soil which characteristically in forests is covered in litterfall from the trees and shrubs. This year we did see a good amount of rainfall which should have increase the water availably to ground, with the increase in water it better has a chance to reach the soil and seeds giving the herbaceous vegetation this year more of one of one of the key things they need to grow.

3. Introduction -nearby 3 tree species that populate this region
-they share similar elevations, slopes, and aspects
Populus tremuloides: (Aspen)
-deciduous leaves
Pinus contorta (Lodgepole pine)
-evergreen needles
Picea engelmannii (Engelmann Spruce)
Nearby we seem to see 3 main three species, they are the aspen tree, lodgepole pine, and engelmann spruce. They overlap in distribution and can share similar elevations, slopes, and aspects. They have one main characteristic that differentiates them. They leaves/needles we see are quite different. Aspens, most obviously, have deciduous leaves that fall annually while the pine and the spruce have evergreen needles that are produced to be much tougher, lasting longer on the trees and having lower decomposition rates.
-deciduous leaves fall annually, less work is put into producing long lasting leaves, they should break down faster reducing litter pile up on top of soil
-evergreen trees require more energy to produce and are rough to break down which could lead to larger litter piles that could negatively affect ground vegetation
Aspen leaves picture:
Lodgpole picture:
Spruce picture:

4. Question
Does the species of tree canopy cover differently affect ground vegetation occurrence and/or abundance?
My question is are we going to see differences in the vegetation abundance under the different species of canopy? Are we going to see a correlation between percent cover of herbaceous vegetation and litter depth?

5. Hypothesis
Null: There is no difference in ground vegetation under the different canopies
Alternative: There was an observable difference in ground vegetation between canopies
H0: we did not see any statistical difference in the ground vegetation under the different species of canopy
H1: we did se a statistical difference of ground vegetation under the different species of canopy

6. Methods -Random sampling of 6 sites, 2 Lodgepole, 2 Spruce, 2 Aspen
My methods starting out with finding 6 different sites, two of each of the three species giving us a total of 6 sites. I used a buffer line to make sure that my observed site had homogeneity within. And then the random numbers sheet to find random numbers along my buffer line then out to find a random plot.
Aspen photo: my own
Lodgepole photo:
Spruce photo:

7. Methods Cont. Sunlight Penetration:
-Canopy Mirror Method (Canopy Cover %)
-densely covered areas used -(92%-97% coverage)
Litter accumulation:
-Litter Depth, cm
Water availability:
-Slope/Aspect
Herbaceous vegetation abundance:
-60 Daubenmire Plots (% Cover)
-10/site
-herbaceous, litter
Once I found my plots I wanted to test for the three main factors that can contribute to herbaceous vegetative growth in the understory. I used to canopy mirror method to test for canopy density and sunlight penetration, I wanted the areas to be within dense forests and see if certain types of trees allow more sunlight than others. Then to test for the litter accumulation I measured the depth of the litter in cm. To make sure that all sites have similar water availably I measured slope and aspect to make sure those were almost the same. Finally to deter the differences in herbaceous vegetation I used Daubenmire plots (20x50cm) to measure % cover of vegetation and litter. 10 Daubenmires were done at each site giving 20 for each species and 60 overall.
Limitations: measuring the soil moisture content would have helped to measure water availably but there was no instrument available here to measure that. It could have helped me to measure if the water was reaching the soil or if it was used up in the litter.
Photo: my own

8. Results ANOVA: -Herbaceous Cover -p-value: <.0001 -Litter Cover
-Litter Depth
-p-value <.0001
I used ANOVA, analysis of variance to compare my three sites. The herbaceous cover, litter cover, and litter depth all had significant p vales which means that there is less of chance of the differences being a coincidence. In the graphs we can see that the one that stands out as different is the Aspen sites. It shows higher % herbaceous cover and lower litter depths and % litter covers.

9. Results Litter depth v herbaceous cover Litter cover v litter depth:
Variable differentiate by factor of 10
For comparison I had litter depth vs herbaceous cover, and we can see a negative correlation between the two factors. The higher the depth the lower the herbaceous cover. And the lower the depth the higher the herbaceous cover rises. Then I compared the litter cover and the litter depth, these factors seem the fluctuate at the same degree. The more the litter depth the higher the percent cover of litter which also ties into the herbaceous cover.

10. Results Canopy Cover : -p-value: .0603 Number of Species:
The p value for the canopy cover was not significantly different. The densities of canopy were similar which means that light doesn’t necessarily penetrate one species of canopy more than the others. The number of species p value was significantly different and we can see that Aspen forest did have the most species but spruce forests also had a relatively high number of species.

11. Results Summary ANOVA: P-values -Herbaceous % Cover <.0001
-Litter depth <.0001
-Litter % Cover <.0001
-Canopy Cover <.0603
-number of species <.0001
-results show observable differences in ground vegetation under 3 species of canopy cover
-most notably under aspen trees
Overall the only number that was not significant was the canopy cover %. Telling us that the sunlight penetration was not the main factor for why the herbaceous cover was so different in the sites. And all of the other measured factors showed significant difference telling us that there is statistically significant differences in the herbaceous ground vegetation fo the different species canopies.

12. Discussion
Why?
Water availability and Sunlight Penetration were similar at all sites
Difference: Litter
-Litter composition:
-mainly needles/leaves
Needle/Leaf composition: Evergreen vs Deciduous
-Aspen leaves can break down in about a year (Alban, 1982)
-faster decomposition = less litter builds up
-soil more susceptible to blowing/dropping seeds
-water hits soil almost directly, reaching seeds/roots
So why are there differences in the ground herbaceous vegetation under the different species of canopies? From our data we saw that litter depth had a negative correlation with the herbaceous cover. Since sunlight penetration wasn’t significant and water availability was controlled for this leaves the litter accumulation as our main suspect for the differences we saw. So then why was the litter different in the different locations. The compsitons is different because of the leaves needles that fall into it. Aspen litter is mainly made up of aspen leaves which do fall more frequently as they are deciduous but they are also much easier to break down. Microbial populations can break down the aspen trees to unrecognizable material in about a year (Alban, 1982). While evergreen needles don’t fall as frequently but are much much more difficult to break down because of how tough they are. Since they are so difficult to break down this can lead to the accumulation of higher litter depths which seems to impede the ground vegetation abundance. Also with the aspen litter the soil is more exposed than the spuce and pine soil giving the water a better chance of reaching it and seed a better chance of germinating and the stems have an easier time to penetrate what little litter is there.

13. Further Research
-litter decomposing's effect on soil composition of the three areas
-adequate soil composition for herbaceous growth
-leaf/needle decomposition adds different nutrients into soil that could promote or impede herbaceous growth
-is litter composed of needles more difficult for vegetation to breach than litter of aspen leaves, or water to reach soil?
Further research that could be done to determine if litter is a large contributing factor is looking at the soil and litter chemical composition. When the microbial communities break down this material they are releasing chemicals. Depending on what chemicals or in what concentrations this could have an effect on the vegetation community. And another factor that could use further research is whether there is a maximum depth for species that they cant penetrate the litter to reach the sunlight or if adequate water is making its was through the litter to the soil.

14. Conclusion
-ground vegetation is more abundant under aspen trees than pine and spruce
-litter depth significantly lower
-correlates with:
-more % herbaceous cover
- less % litter cover
In conclusion we saw that there were significant differences in the herbaceous ground vegetation between the different species of canopies. Aspen showed to be more advantageous for the herbaceous vegetation while pine and spruce had less herbaceous vegetation productivity. We saw correlations with the litter depth and the amound of % herbaceous cover and % litter cover.

15. References/Lit Cited
Alban David H., Effects of Nutrient Accumulation by Aspen, Spruce, and Pine on Soil Properties Soil Science Society of America Journal, 46 (4) , (1982)
Harrington timothy b, Edwards m boyd Understory vegetation, resource availability, and litterfall responses to pine thinning and woody vegetation control in longleaf pine plantations Canadian Journal of Forest Research, (1999)
Laurent Augusto, Jean-Luc Dupouey, Jacques Ranger Effects of tree species on understory vegetation and environmental conditions in temperate forests Annals of Forest Science 60 (8) (2003)
Werner Härdtle, Goddert von Oheimb, Christina Westphal, The effects of light and soil conditions on the species richness of the ground vegetation of deciduous forests in northern Germany (Schleswig-Holstein), Forest Ecology and Management, 182, (1–3) , (2003)