When do trees grow (2)?

Tree species have their specific climatic niches in which they grow. Norway spruce at the subalpine site Seehornwald Davos grows best at temperatures around 12°C whereas Scotts pine shows optimal growth at around 16°C. Too cold or too hot temperatures inhibit growth processes.

Strongly limiting for growth is the dryness of the air (quantified as vapor pressure deficit, VPD) particularly for the subalpine Norway spruce trees. Wood growth occurs only in periods when VPD is lower than 1 kPa. Such VPD values are exceeded at almost any sunny day. More tolerant is Scotts pine. However, wood growth is limited to relatively wet conditions also for this species.