Chapter 8 A Markov Analysis of Tree Islands at Alpine Treeline

Abstract

Abstract The pattern of conifer establishment and the potential role of positive plant interactions in tree islands at alpine treeline are examined at three treeline locations in Glacier National Park. Tree island development is often initiated by the establishment of a conifer near a microtopographic shelter source, and subsequent establishment creates a linear, series-like pattern in the lee of previously established trees. First-order Markov analysis of series pattern of established individuals in tree islands demonstrates relative stability or self-perpetuation of many of the early-established individuals, lowering the number of predominant vegetation classes. Embedded Markov analysis, however, suggests that the establishment of conifers within a patch does not follow a predictable spatial sequence; however, Pinus albicaulis , a foundation and keystone species, occupies sites immediately behind shelters more than other species and therefore may facilitate subsequent conifer establishment. The spatial patterns of these treeline series are highly variable with study sites, as would be expected from the highly variable local environments of these sites and a largely structural facilitation regime. Where species richness and patch dynamism is high, there may be greater potential for treeline advance on a coarse scale than there is at sites with low species richness. Low richness sites may be more susceptible to stochastic disturbance events that would disrupt conifer establishment and survival.