||Low temperature limits cambial activity and determines secondary growth at the alpine treeline|
||Lenz A, Hoch G, Körner Ch
||Plant Ecology and Diversity. in press doi:10.1080/17550874.2012.711864|
Background: Temperature directly affects xylogenesis at high elevation treelines. The low temperature limitation of meristematic processes is thus key to understand treeline formation.|
Aims: Experimentally test the direct low temperature influence on wood tissue formation at the alpine treeline in situ.
Methods: We applied controlled Peltier-mediated cooling and warming (±3 K) to branch segments in P. uncinata at the alpine treeline in the Swiss Alps. In addition, we studied xylogenesis in untreated trees during the growing season by sequential microcoring.
Results: Surprisingly, microcores revealed that the cambial zone was fully developed by the time the cooling and warming treatment started shortly after snowmelt. Presumably, because of this, experimental cooling of branches did not significantly reduce the number of cells produced per season. Warming extended the formation of earlywood into the late season, and thus, reduced the fraction of cells becoming latewood.
Conclusions: We conclude that temperatures very early in the season determine the width of the cambial zone, which in turn strongly controls the number of tracheids produced during the remaining growing season. Temperatures later in the season mainly determine the earlywood-latewood ratio. These data provide an empirical basis for the mechanistic understanding of tree growth at treeline in response to temperature.
||cambial zone, cambium, cooling, Pinus uncinata, timberline, warming, xylogenesis, snowmelt
||Christian Körner: email | webpage|
Armando Lenz: email | webpage