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In The Subalpine Conifer Forests of Colorado, Will Fallen Trees
Affect The Percent Cover of Understory Vaccinium Shrubs?
Alex RobertsonVegetation Ecology
2013
IntroFrom a study on windows of opportunity for
Vaccinium species, Eriksson and Fröborg (1996) found that decaying wood is a highly favorable substrate for Vaccinium species.
Would their findings hold true in Colorado’s subalpine forest with fallen Engelmann spruce (Picea engelmannii) and Subalpine fir (Abies lasiocarpa).
Fallen trees offer a potential window of opportunity for understory growth.
HypothesisPredict that the percent cover of understory species will be
greater around fallen trees.Reasons:
More organic matter available Greater access to sunlightIncreased moisture content
Methods1. 50(m) x 50(m) plot with at least 5
fallen trees.2. Fallen trees DBH > 10(cm).3. Point frame method at top and
bottom of each fallen tree4. Record number of contact points
and species name.5. Record location of sample sites6. Random location of 10 sampling
sites where no fallen trees are present. Being sure to stay within the 50(m) x 50(m) plot.
7. Point frame method at each random location.
Sample SiteKey:• Fallen tree =• Sampling location = (fallen trees)• Sampling location =
(open areas)
top trun
k
top
top
trunk
top trun
k
top trunk
trunk
50 (m)
50 (m
)
Results• P-value = 0.5499 > 0.05,
so I cannot reject my null hypothesis.
• There is no significant relationship between Vaccinium percent cover for these two sites.
• Standard Error for Fallen = 0.068
• Standard Error for Open Area = 0.062
Fallen0.26
0.27
0.28
0.29
0.3
0.31
0.32
0.33
0.34
0.336
0.288
Average % Cover
Open AreaA
vera
ge P
erce
nt C
over
Average Percent Cover of Vaccinium myrtillus Between Fallen Trees and Open Space
Results• Samples taken by fallen trees
reveal greater average percent cover at the top, compared to the trunk of the tree.
• P-value = 0.057 > 0.05• T-test of the samples reveal
that there is no significant difference in percent cover between these sites, but close.
• Standard error for the trunk = 0.072
• Standard error for the top = 0.109
Trunk0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.248
0.424
Top
Average Percent Cover of Vaccinium at Trunk and Top of Fallen Trees
Ave
rage
Per
cent
Cov
er
Discussion• Eriksson and Fröborg (1996)
found that decaying wood is a favorable substrate for Vaccinium, but my findings do not adhere to their results.
• Window of opportunity must align in time with Vaccinium fruiting and seed dispersal.
• Would other species present in the understory provide different results?
• What is the relationship among Vaccinium percent cover for fallen trees between the trunk and top of the tree.
Summary“The occurrence of decaying wood is spatially
unpredictable in coniferous forests but at least in natural or semi natural forests not temporally unpredictable” (Eriksson, Fröborg 1996).
Need to consider the timing of seed dispersal for understory species in relation to windows of opportunity and percent cover of the forest floor.
Fallen trees alone are not enough to increase percent cover for Vaccinium myrtillus.
References"Comprehensive Report Association - Abies Lasiocarpa - Picea
Engelmannii / Vaccinium Myrtillus Forest." Comprehensive Report Association - Abies Lasiocarpa - Picea Engelmannii / Vaccinium Myrtillus Forest. Nature Serve, n.d. Web. 17 July 2013.
Eriksson, Ove, and Heléne Fröborg. ""Windows of Opportunity" for Recruitment in Long-lived Clonal Plants: Experimental Studies of Seedling Establishment in Vaccinium Shrubs." Botany 74.9 (1996): 1369-374. Print.
"Standard Error." Definition. N.p., n.d. Web. 17 July 2013."Window Of Opportunity." Definition. N.p., n.d. Web. 17 July
2013.
Appendix I
1 2 3 4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Fallen
Open Area
Sample Number
Per
cent
Cov
er
Percent Cover of Vaccinium myrtillus in CO Subalpine Conifer Forest
• High variability in percent cover for Vaccinium myrtillus throughout all sampling sites