Community Structure, Biodiversity, and Ecosystem Services in Treeline Whitebark Pine Communities: Potential Impacts from a Non-Native Pathogen

Abstract

Whitebark pine (Pinus albicaulis) has the largest and most northerly distribution of any white pine (Subgenus Strobus) in North America, encompassing 18˝latitude and 21˝longitude in western mountains. Within this broad range, however, whitebark pine occurs within a narrow elevational zone, including upper subalpine and treeline forests, and functions generally as an important keystone and foundation species. In the Rocky Mountains, whitebark pine facilitates the development of krummholz conifer communities in the alpine-treeline ecotone (ATE), and thus potentially provides capacity for critical ecosystem services such as snow retention and soil stabilization. The invasive, exotic pathogen Cronartium ribicola, which causes white pine blister rust, now occurs nearly rangewide in whitebark pine communities, to their northern limits. Here, we synthesize data from 10 studies to document geographic variation in structure, conifer species, and understory plants in whitebark pine treeline communities, and examine the potential role of these communities in snow retention and regulating downstream flows. Whitebark pine mortality is predicted to alter treeline community composition, structure, and function. Whitebark pine losses in the ATE may also alter response to climate warming. Efforts to restore whitebark pine have thus far been limited to subalpine communities, particularly through planting seedlings with potential blister rust resistance. We discuss whether restoration strategies might be appropriate for treeline communities.

The Importance of Conifers for Facilitation at Treeline: Comparing Biophysical Characteristics of Leeward Microsites in Whitebark Pine Communities

“…However, the prevalence of P. albicaulis as a tree island initiator is generally predicted by its high relative abundance as a solitary tree, which may result from seed dispersal by Clark's nutcrackers to protective microsites at treeline and greater seedling hardiness. In fact, Tomback et al (2016) found that the proportional abundance of P. albicaulis among solitary trees in the ATE across 10 study areas predicted its proportional abundance as a tree island initiator.…”

Whitebark pine facilitation at treeline: potential interactions for disruption by an invasive pathogen

“…Previous studies show P. albicaulis to be the most prevalent solitary tree in many, but not all Rocky Mountain treeline communities (Tomback et al. , ). For 10 study areas across the Rocky Mountain distribution of P. albicaulis , Tomback et al.…”

“…; Tomback et al. , ). Tree island initiation involves the initial establishment of an isolated or solitary krummholz conifer followed over time by the establishment of other conifers in its lee.…”

Vegetation Diversity and Intensity of Plant Pests and Diseases in Two Polyculture Systems in Tanggamus District

“…Some research results showed that agrochemical treatments (especially pesticide an fertilizer) had caused problem social and environmental changes (Altieri et al, 1984;Altieri, 1999;Scherret al, 2008). Agricultural and forestry environment managements are keys for conservation of diversity which significantly improve richness and abundances of species, while tree able to reduce able to improve pest, pathogen incidence, and also to provide ecology services in strengthening beneficial insects (Batary et al, 2011;Tomback et al, 2016;Aluja et al, 2014).…”