Tree Growth near Treeline: Abrupt or Gradual Reduction with Altitude?

摘要: Natural climatic treelines are relatively discrete boundaries in the landscape established at a certain elevation within an otherwise continuous gradient of environmental change. By studying tree rings along elevational transects and below upper treeline European Alps, we (1) determine whether radial stem growth declines abruptly or gradually, (2) test influences on trees near by investigating for climatically different historical periods. While height decreases gradually toward treeline, there is no such general trend growth. We found rather abrupt changes which imply threshold effects temperature moved upslope wave-like manner as temperatures increased over past 150 yr. Currently Alps same magnitude several hundred meters current treeline. Over short intervals, tree-ring width more dependent interannual variability than altitudinal distance to conclude that response tree-rings includes component (a minimal seasonal temperature) strongly correlated with year variation climate such. Our data indicate position reflects climates not climate.