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

Area of Science:

• Ecology
• Plant Biology
• Forest Science

Background:

• Facilitation is key for plant establishment in stressful environments like treelines.
• Invasive pathogens can disrupt these beneficial plant interactions.
• Pinus albicaulis initiates tree islands more frequently than other conifers in the Rocky Mountains.

Purpose of the Study:

• To investigate the facilitative role of Pinus albicaulis in conifer establishment at treeline.
• To determine which life-history stages of leeward conifers benefit from P. albicaulis.
• To assess the impact of Cronartium ribicola-induced P. albicaulis mortality on leeward conifers.

Main Methods:

• Experimental examination of plant-plant interactions in two Rocky Mountain study areas.
• Assessing seed germination and seedling survival in microsites associated with P. albicaulis.
• Simulating P. albicaulis mortality from C. ribicola to observe effects on leeward krummholz conifers.

Main Results:

• P. albicaulis microsites offered the highest odds of cotyledon seedling survival.
• More seeds germinated in leeward rock microsites compared to exposed or conifer microsites.
• Simulated P. albicaulis mortality reduced shoot growth in leeward conifers.

Conclusions:

• P. albicaulis provides significant facilitation for early conifer life stages at treeline.
• Mortality of P. albicaulis due to Cronartium ribicola disrupts these facilitative interactions.
• Loss of P. albicaulis may impede treeline conifer community development and upward migration with climate change.