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

• Published in: Canadian journal of forest research Vol. 45; no. 10; pp. 1299 - 1312
• Main Authors: Millar, Constance I, Robert D. Westfall, Diane L. Delany, Alan L. Flint, Lorraine E. Flint
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.10.2015; Canadian Science Publishing NRC Research Press
• Subjects: basins; changement climatique; Climate; climate change; Climatic changes; climatic factors; conifers; croissance radiale; dendrochronologie; dendrochronology; ecotones; forests; growing season; growth rings; limite des arbres; mountains; Pine; Pinus flexilis; Pinus longaeva; Plant growth; Plant populations; radial growth; recruitment; recrutement; temperature; tree line; treeline; Trees; United States; Great Basin; USA, Great Basin; USA
• ISSN: 1208-6037; 0045-5067; 1208-6037
• DOI: 10.1139/cjfr-2015-0025

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.