Treelines Will be Understood Once the Functional Difference Between a Tree and a Shrub Is

Abstract

Trees are taller than shrubs, grasses, and herbs. What is the disadvantage of being tall so that trees are restricted to warmer regions than low stature life forms? This article offers a brief review of the current state of biological treeline theory, and then explores the significance of tallness from a carbon balance, freezing resistance, and microclimatological perspective. It will be argued that having of a woody stem is neither a burden to the carbon balance nor does it add to the risk of freezing damage. The physiological means of trees to thrive in cold climates are similar to small stature plants, but due to their size, and, thus, closer aerodynamic coupling to air circulation, trees experience critically low temperatures at lower elevation and latitude than smaller plants. Hence, trees reach a limit at treeline for physical reasons related to their stature.

Tree Height-Diameter Relationships in the Alpine Treeline Ecotone Compared with Those in Closed Forests on Changbai Mountain, Northeastern China

“…Beyond 1900 m a.s.l., trees become more stunted to create a more suitable microclime in order to survive. The stature of multiple tree species in several prominent mountain ranges was also found to become dramatically stunted across a relatively small altitudinal range of only 50 to 100 m below the treeline [26,27]. These results suggest that tree stature change is much faster or even abrupt in the alpine treeline ecotone or close to the alpine treeline.…”

“…on Changbai Mountain (see Table S2 in Supplementary Materials). It has been reported that when soil temperature is lower than 5 • C, a very small reduction in soil temperature may lead to a dramatic increase in the time required for mitotic division of plant cells and a doubling in the time needed for cell reproduction [27]. Moreover, resource allocation from storage tissues to a tree's apical meristems (height growth) yields a relatively lower reward relative to xylem (radial growth) due to the longer transport pathway [28].…”

“…Three meters has conventionally been adopted as the height distinguishing shrub and tree growth forms (irrespective of branching pattern) [27]; this height ensures that a 'tree' has its crown closely coupled to prevailing atmospheric conditions. In this study, we found that a tree height of 2.25 m serves as the inflection point for the trend in the height-diameter relationship (Figure 2).…”

Holocene treeline and timberline changes in the South Carpathians (Romania): Climatic and anthropogenic drivers on the southern slopes of the Retezat Mountains

“…Signs of upward treeline and timberline shifts have already been detected in several decadal-scale studies (Harsch et al, 2009;Heiri et al, 2014;Körner, 2012b;Theurillat and Guisan, 2001;Tinner and Ammann, 2005), supporting predictions that ongoing global warming leads to rises in treeline and timberline with corresponding reductions in alpine grassland .…”

The Man, the Myth, the Legend: Professor Terry V. Callaghan and His 3M Concept

“…Hence, this special issue presents papers on monitoring Hedenås et al 2012;Körner 2012;Christensen et al 2012), on manipulations (Michelsen et al 2012;Cornelissen et al 2012;Bokhorst et al 2012;Gwynn-Jones et al 2012;Keuper et al 2012), and finally, papers on modeling (Miller and Smith 2012;Yang et al 2012;Hein et al 2012). Fig.…”