1. Vegetation Composition in Niwot’s Riparian Tundra
Sean Race, 2014, Vegetation Composition in Niwot’s Riparian Tundra [pptx, M] Keywords: Riparian proximity, Tundra
Sean Race
Vegetation Ecology – Semester B 2014
Mountain Research Station. UC-B

2. Introduction
Question: Does proximity of riparian area in alpine tundra affect the composition of the vegetation found there?
Are certain species exclusive to particular areas of the tundra?

3. Hypothesis
H0 : There is no relationship between proximity to riparian area and vegetation composition
Alternate Hypothesis: There is a significant relationship between proximity and vegetation composition
Prediction: Certain species will colonize the different parts of the tundra based on proximity

4. Prior Research
Proximity to water influences the plant diversity and topography of riparian zones compared to uplands (Elmore, Beschta 1987)
Species Richness increases as distance from stream increases,
then falls gradually (Gregory et al. 1991)
Vegetation along arctic river systems is primarily determined by moisture content and pH (Gould, Walker 1999)

5. Methods Site 1 – Fourmile Creek tundra Sites 2&3 – Niwot Ridge tundra
Soils varied between sites… Site 1 had a very boggy soil and even at 10-15m the soil was reasonably mesic. Sites 2 and 3 saw drier soils, mesic near the stream beds and then xeric in the 10-15m samples.
Elevation: 10961ft
Aspect: 120°SE
Slope: 2.5%
Elevation: and 11191ft
Aspect: 112 and 113°SE
Slope: 2% and 5%

6. Plotting techniques
5 Daubenmire plots in 10x5m area 0-5m from stream and 10-15m from stream
Each replicate had 10 plots total
Measured avg. height, species, # individuals, and phenological state
Overall, there were 30 Daubenmire plots across all three replicates (well, 1 replicate and 2 pseudoreplicates). I sampled by individual instead of stem, and estimated cover class as I did this. I think used a meter stick to take the height of a handful of individuals and averaged that out. Additionally, I also sampled phenological state of the vegetation, taking the most advanced member of each species as the baseline.

7. Results
Species Richness did not vary greatly between the Riparian (25) and Off-Riparian (23) samples
More significant were changes in phenological state and between individual species…
Jaccard Index: 0.6
# Common: 18
# Different: 12
On the Chi-Square, I used the test with the Yates correction. This resulted in slightly different values than with the standard Chi-Square test.
P-value:

8. Erigeron vs. Snow Buttercup Chi-Square(s)
Including all cover classes resulted in a p-value of
Removing cover class 1 (0-5%) resulted in a p-value of , however
All Classes
I decided to run this Chi-square both ways due to my observations that there actually was a noticeable difference between the Black-headed Fleabane and the Snow Buttercup in terms of distribution between the two measurement areas. It seems that when you include all classes there isn’t a big difference, but the observational difference in cover/presence is due to a widening gap when taking greater cover classes into account.
Classes excl. 1

9. Yarrow (Achillea millefolium) Chi-Square
A strong relationship between cover class and Yarrow presence exists between the Riparian and Off-Riparian areas
Yarrow dominates the drier Off- Riparian areas while being largely absent from the mesic areas

10. Species Evenness T-Test
No significant relationship between location and species evenness was found
Two-tailed p-value: .846
Riparian Mean: 82
Off-Riparian Mean:83
I included this slide to illustrate that a lot of the changes in the tundra vegetation were on a finely granular level as opposed to a broader level. Although this might have changed with more data (as opposed to only 3 replicates each).

11. Discussion
Differences in species richness and species evenness were minimal between sites
However, vegetation composition based on phenological state and individual presence/absence showed significant trends
Results of Chi-Square tests and Jaccard Index suggest that individual species composition is heavily influenced by proximity to water source
The evenness in species richness was not something I was expecting given other studies on similar subjects, but I suppose it makes sense when the riparian areas of tundra do not have nearly the outsize effect of the large streams and rivers found in subalpine and lower montane areas.

12. Limits and Future Research
Major limits of this study included lack of 3 distinct replicates
More replicates for future studies
T-test on bounded data
Possible ranking system?
A future study could survey larger areas to perhaps see the affect of further distance (>15m) on vegetation composition
Potentially look into differences between native and exotic grass species…
I was unable to get three replicates due to time constraints, and as such I was forced to pick two distinct sites with two pseudoreplicates in the second site. I feel this may have influenced some of the results in terms of species dominance and species evenness. The inability to get a species evenness/diversity calculator to work with only 3 replicates also limited this study. Though, since the data was found to be insignificant by the t-test it is possible this limitation had little influence on the results of the study. In the future I would

13. References
Gould, W. A. and Walker, M. D. (1999) “Plant communities and landscape diversity along a Canadian Arctic river.” Journal of Vegetation Science, 10: 537–548.
Gregory, Stanley V and Swanson, Frederick J et al. “An Ecosystem Perspective of Riparian Zones” Bioscience, Sep 1991: 41, 8. Research Library Core pg. 540
Elmore, Wayne and Beschta, Robert L. “Riparian Areas: Perceptions in Management” Rangelands, Dec 1987: 9, 6: