The effects of wind and temperature on cuticular transpiration of Picea abies and Pinus cembra and their significance in dessication damage at the alpine treeline

Abstract

The importance of high winter winds and plant temperatures as causes of winter desiccation damage at the alpine treeline were studied in the Austrian Alps. Samples of 1- and 2-year twigs of Picea abies and Pinus cembra were collected from the valley bottom (1,000 m a.s.l.), forestline (1,940 m a.s.l.), kampfzone (2.090 m a.s.l.), wind-protected treeline (2,140 m a.s.l.), and wind-exposed treeline (2,140 m a.s.l.). Cuticular transpiration was measured at three different levels of wind speed (4, 10, and 15 ms) and temperature (15°, 20°, and 25° C). At elevated wind speeds slight increases in water loss were observed, whereas at higher temperatures much greater increases occurred. Studies on winter water relations show a significant decline in the actual moisture content and osmotic potentials of twigs, especially in the kampfzone and at treeline. The roles of high winds and temperatures in depleting the winter water economy and causing desiccation damage in the alpine treeline environment are discussed.

A re-assessment of high elevation treeline positions and their explanation

“…As suggested by Kerner (1869, p. 41) over a century ago summer pre-disposition correlates with the degree of winter desiccation, e.g. because of insu cient maturation of leaf cuticles or buds (Baig and Tranquillini 1980;Tranquillini and Platter 1983;Wardle 1981b). Direct damage to needle surfaces by winter conditions such as cuticle abrasion has also been suggested to contribute to excess moisture loss (Holtmeier 1974;Hadley and Smith 1983; see discussion by Grace 1989).…”

Wood Microsites at Timberline-Alpine Meadow Borders: Implications for Conifer Seedling Regeneration and Alpine Meadow Conifer Invasion

“…For example, with climate warming, there is a general expectation that forests will advance, but factors including low substrate moisture, low substrate temperatures, high radiation, fire, and both low and high snow accumulation may limit seedling regeneration and survival, restricting upward advance (Baig and Tranquillini 1980;Callaway 1995;Bansal and Germino 2008;Harsch et al 2009;Tranquillini 2012;M€ uller et al 2016). Upward advance of the alpine treeline ecotone (ATE), the zone ranging from the upper limit of subalpine forest (forest line) to the treeline, is dependent on successful germination and survival of seedlings.…”

Spruce colonization at treeline: where do those seeds come from?

“…Low temperature severely limits tissue formation and seedling growth (Hellmers et al, 1970;Kö rner, 1999). During winter, frozen soil strongly reduces water availability, whereas stems and shoots are exposed to water losses caused by high wind and intensive radiation (Baig and Tranquillini, 1980). Drought stress combined with frequent freezethaw events causes embolism damage in forest trees such as Norway spruce (Mayr et al, 2003).…”