Recruitment patterns and growth of high-elevation pines in response to climatic variability (1883–2013), in the western Great Basin, USA

Abstract

Over the period 1883–2013, recruitment of subalpine limber pine (Pinus flexilis E. James) and Great Basin bristlecone pine (Pinus longaeva D.K. Bailey) above the upper tree line, below the lower tree line, and across middle-elevation forest borders occurred at localized sites across four mountain ranges in the western Great Basin. A synchronous pulse at all ecotones occurred between 1963 and 2000 (limber pine) and between 1955 and 1978 (bristlecone pine) when pines expanded 225 m beyond forest borders. Little recruitment occurred before this interval or in the 21st century. No obvious environmental factors distinguished recruitment locations from nonrecruitment locations. Where their ranges overlap, limber pine has leapfrogged above bristlecone pine by 300 m. Limber pine tree-ring chronologies, developed to compare radial-growth responses with recruitment, showed dominant pulses of increased growth during the same interval as recruitment. Significant climate correlations of growth and recruitment indicated lead and lag effects as much as 6 years and complex relationships with climate variables, corroborating the importance of cumulative climate effects relative to any single year. Water relations were the most important drivers of growth and recruitment and interacted with growing-season minimum and maximum temperatures. These results underscore the importance of studying ecotones at all margins when evaluating conifer response to climate change.

Soil Preferences in Germination and Survival of Limber Pine in the Great Basin White Mountains

“…I collected all soil on the same day in late October and sowed the seeds the day after soil was collected. bristlecone pine treeline on dolomite, an alternative hypothesis is that limber pine prefers soil types on which it is rarely found as an established adult [19,20]. This study first examines the relative abilities of different soil types to retain water over shorter (days) and longer (months) time scales.…”

“…Sub-alpine stands of Engelmann spruce (Picea engelmannii Parry) and quaking aspen (Populus tremuloides Michaux) can also be found on wetter slopes in the eastern Great Basin, and whitebark pine (Pinus albicaulis Engel) stands are found in parts of the northern and eastern Great Basin as well as on the eastern slope of the Sierra Nevada. Recent studies of Great Basin sub-alpine forests have shown that treeline is advancing through upslope establishment of young trees, but that this establishment has occurred only very recently and in infrequent pulses [19]. In addition, it appears that even though bristlecone pine is usually the dominant adult tree at treeline where it is found, typically downslope limber pine is responsible for the majority of treeline advance in these stands, with young trees "leap-frogging" over treeline adult bristlecone pine [19,20].…”

“…Recent studies of Great Basin sub-alpine forests have shown that treeline is advancing through upslope establishment of young trees, but that this establishment has occurred only very recently and in infrequent pulses [19]. In addition, it appears that even though bristlecone pine is usually the dominant adult tree at treeline where it is found, typically downslope limber pine is responsible for the majority of treeline advance in these stands, with young trees "leap-frogging" over treeline adult bristlecone pine [19,20]. This mismatch is especially acute on certain soil types where bristlecone pine adults dominate the sub-alpine forests, but the vast majority of upslope establishment is limber pine [20].…”

“…In the western Great Basin both bristlecone pine and limber pine are found across all three Great Basin soil types, allowing for an explicit comparison of soil preference at the leading edge of treeline species. Where bristlecone pine is present, it is typically the dominant tree at treeline with the exception being on granitic soils where limber pine typically dominates [19,20]. Bristlecone pine is especially dominant on dolomite soils where nearly pure stands are often found to treeline [23].…”

Climate Change Refugia, Fire Ecology and Management

“…Hotham in Australia [40]. In the White Mountains of California, bristlecone pine are expanding downhill into local cold-air pools as temperatures warm [41]. Lesser known examples in the CAPs of Yosemite National Park in California include the Merced Grove, with disjunct distributions of species more characteristic of the Pacific Northwest, such as mountain lady's slipper (Cypripedium montanum) and Old-man's-beard Lichen (Alectoria sarmentosa), growing together with Sierran species.…”