1. Vegetation Dynamics of the NE and NW slopes of Betasso Preserve
Jared Lucero
Vegetation Ecology
University of Colorado Mountain Research Station
July 23rd, 2015
Vegetation Dynamics of the NE and NW slopes of Betasso Preserve
Jared Lucero
Vegetation Ecology
University of Colorado Mountain Research Station
July 23rd, 2015
Ponderosa Pine, Density, Percent cover, aspect, Betasso Preserve, Litter, Daubenmire, Point-Quarter, North West Slope, North East Slope, Vegetation, herbaceous material, Under story, Over Story

2. Question Is there a significant difference in the vegetation that
grows within the North East slope relative to the North
West slope in terms of percent cover and density?
I wanted to measure two types of variables in my project. The first being the percent cover of herbaceous undergrowth and the second being the density of trees at each aspect. This leads me to why this is important to study.

3. Importance Known relationship between S & N facing
Known relationship between E & W facing
Two sites that have slightly different aspects
Good to know all aspects
Enough influence on north facing slopes
Ecologists have studied the differences between north and south facing slopes and have determined that they differ in soil and air temperature which may lead to different types of community structures and spatial arrangement (density) and percent cover of the vegetation. East and west slopes are known to have differences in the same to variables when it comes to the rainshadow effect. We know that as wet wind comes from the north it cools and rises up over the mountains and then on the leeward side of the mointain the air dries as the temperature increases. This may be an interesting factors to combine two different types of aspect, in this case, NE and NW.

4. Exposure induced differences in vegetation (Cantlon J. 1953)
Environmental differences in S & N, similarly E &W
East versus west rainfall contributing to higher species diversity
Spacial associations between overstory and understory- increase gradients (R. Michalet, 2003)

5. Hypotheses
Null. The percent coverage of herbaceous vegetation will not be
Different between the NE & NW slope
Alternative. The percent coverage of herbaceous vegetation will be different
Between the NE & NW slope
Null. The density of Ponderosa Pine will be different between the NE & NW slope
Alternative. The density of Ponderosa Pine will not be different between the NE & NW slope
I had to come up with four different hypotheses because for this experiment I needed to separate the ponderosa pine density from the percent coverage of herbaceous material on the understory considering that both communities would not remain uniform as I moved throughout the different sites.

6. Betasso Preserve, CO
So moving on to my methods, I decided that Betasso played host to a variety different aspects. I would easily be able to find a couple north east and north west facing slopes with the community structure being relatively consistent, as opposed to going to a completely different site and measuring the two variables of tree density and total herbaceous vegetation coverage.

7. North West Slopes; 2 sites
Trees dense,
Litter: Pine needles
Patchy understory,
herbaceous vegetation
~0.3m high.
For the North West slopes I chose two sites, one at 335 NW, and the other at 290 NW. I immediately noticed that the trees were dense, the litter was made up mostly of pine needles and there was a very patchy understory.

8. North East Slopes; 2 sites
Trees with large diameter
Not much coverage
Herbaceous vegetation ~0.4m
Cactus
Litter: Soil & needles
Moving on to the North East slopes I saw that there were trees that had a larger diameter with much more herbaceous material on the ground. The soil was a mixture of both needled and thick/wet soil.

9. Methods
Found the aspect for 2 North West facing slopes and 2 North East Facing slopes.
For each slope a base line was created (50m) and by stratified random sampling, 5 Daubenmires were placed in at each site.

10. For each Daubenmire, the percent cover of the vegetation was surveyed.
..Continued
For each Daubenmire, the percent cover of the vegetation was surveyed.
At each site for the Daubenmire a point quarter method was used to analyze the tree density.

11. Results

12. The test was insignificant most likely because they have the same undergrowth but different types of species. The two different slopes are facing a north aspect so they should be similar (somewhat) in their composition of undergrowth and the plants that are actually able to survive there.
T-Test P-value:

13. T-Test P-value: 0.711722791 Jaccard: 0.42
There is a large standard error in this ttest and this may be due to the fact that near these slopes there are the same type of vegetation that grow. I was looking to see if there was a difference in the type of vegetation that occurred in each NW and NE facing slopes but the numbers turned out to be pretty similar. One of the more interesting things I noticed was that there was much more cactus in the NE facing slopes. Maybe this points to a larger question of drought periods within the less dense ponderosa pine forests, therefore they are able to grow more easily. Not as many similarties in species but there was the same amount of diversity.
T-Test P-value:
Jaccard: 0.42

14. This is interesting that at the north west facing slope has more percent cover of litter. This may be due to the act that the density of the trees was greater than that of the north east facing slope. Also this side had more litter that was composed of pine needles, it took quite a bit of digging before getting to the actual soil which at that point was pretty dry. The north east facing slope had more of a soil component to the litter with few pinecones. There were not as dense of trees (as you can see in the following slides) which may contribute to the fact that there is less litter cover and simultaneously more herbaceous material at sites that were not randomly chosen.
T-Test P-Value:

15. This was one of the most significant sets of data that I recorded because the two different aspects had differences in the density of trees. Although the P-value does not show that the data was significantly different, if more data was collected from different sites then it would show up better.
T-test P-value:

16. I was able to notice that at the north east facing slopes the trees were somewhat thicker. But the tests that were performed did not show that the data was significant enough to show this. On average however it may go to say that the trees may have less competition when there is a smaller density of trees in the area, which was seen in the previous slide.
T-test P-value:

17. Discussion
Herbaceous undergrowth similar (Percent cover & species) – Accept Null
Greater litter cover in the NW slope
Greater tree density in NW slope – Reject the Null
Tree diameter not different
Not much similarity in species, but same diversity
As R Michalet had stated in their published paper, there is an association between over and understory. But on this scale maybe there was not much of a difference. Since the preserve was very compact with slopes heading in different directions for every 100 meters you walked, it might have been the case that this vegetation in the understory just adapted to living in both conditions in the North east and North west. Litter cover was interesting to look at because this showed that between the two sites, there was more opportunity for plants to grow in the NE facing slope as opposed to the needle ridden NW slope.

18. NW and NE slopes receive the same amount of rainfall but NW is drier and hot for most of the day
NW slope- dense trees = more litter = less herbaceous coverage
NE slope- less dense trees = less litter = more herbaceous material

19. More than aspect, overstory effects understory
Limitations

20. Conclusion Slopes are variable within the Ponderosa Pine Forest
Overstory effects understory
Depending on the aspect, there may be a list of factors that influence vegetation growth
Samples samples samples!
Human error, the take home message is that there need to be more trials that will dictate whether there are actually differences between two different slopes.

21. References.
Cantlon, J. (1953). Vegetation and Microclimates on North and South Slopes of Cushetunk Mountain, New Jersey. Ecological Monographs, 23(3), Retrieved July 17, 2015, from Michalet, R., Rolland, C., Joud, D., Gafta, D., & Callaway, R. (2003). Associations between canopy and understory species increase along a rainshadow gradient in the Alps: Habitat heterogeneity or facilitation? Plant Ecology, 165(2), Retrieved July 17, 2015, from

22. The End.