Alex Robertson Vegetation Ecology 2013

Intro From 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.

Hypothesis Predict that the percent cover of understory species will be greater around fallen trees. Reasons:  More organic matter available  Greater access to sunlight  Increased moisture content

Methods 1.50(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 tree 4.Record number of contact points and species name. 5.Record location of sample sites 6.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 Site Key: Fallen tree = Sampling location = (fallen trees) Sampling location = (open areas) top trunk top trunk top trunk top trunk trunk 50 (m)

Results P-value = > 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 = Standard Error for Open Area = 0.062

Results Samples taken by fallen trees reveal greater average percent cover at the top, compared to the trunk of the tree. P-value = > 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 = Standard error for the top = 0.109

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 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): Print. "Standard Error." Definition. N.p., n.d. Web. 17 July "Window Of Opportunity." Definition. N.p., n.d. Web. 17 July 2013.

Appendix I High variability in percent cover for Vaccinium myrtillus throughout all sampling sites