Seasonal and daily cycles of stem radial variation of Pinus pinaster in a drought-prone environment

Abstract

a b s t r a c tHigh resolution measurements of stem diameter variation can provide valuable information on the growth process as well as the tree water status. This study investigates the hourly variations in stem radial increment of maritime pine growing on the west coast of Portugal, under a Mediterranean climate with a pronounced summer drought. We tested the hypotheses that (1) stem radius variation in maritime pine has a daily and seasonal pattern that reflects the availability of water and (2) that once the internal water storage is depleted the tree enters a quiescent state. During 2010, stem radius variations were monitored in four similar trees with automatic dendrometers. Tree water deficit was extracted from the stem radial variation. The stem cycle approach was used to divide the daily cycles into contraction, recovery and increment phases. The seasonal cycle was divided into five periods: winter dormancy, spring growth, pre-summer contraction, summer quiescence and autumn re-hydration. Amplitude and duration of each phase were calculated for each cycle and correlated with precipitation, maximum and minimum temperature. Continuous positive radial increment started in spring and reached its maximum by the end of June. A shrinking period was observed in summer, with amplitudes of contraction and recovery 10 times higher than in the other periods. The inability of the trees to recover from the water lost due to transpiration was responsible for stem shrinking and quiescence observed during summer. In autumn, a period of re-hydration and rapid expansion was observed after precipitation, restoring the tree to a physiologically active state. Daily variations in stem radius of maritime pine were mainly determined by the course of transpiration and thus dependent on temperature and tree water status.

Species-specific weather response in the daily stem variation cycles of Mediterranean pine-oak mixed stands

“…To better describe stem radial variation throughout the year, dendrometer series were 210 divided into five periods or seasons according to Vieira et al, (2013) …”

Sensitivity of pines in Mexico to temperature varies with age

“…Younger trees had more monthly climate variables related to growth than older trees, showing that the growth in P. cooperi varies as the trees age. The different temperature responses of trees imply that the stem contracts during the day, due to transpiration and photosynthesis and expands during the night when water reserves are gradually replenished, which translates in a better overnight hydration (Vieira et al, 2013). Thus, warmer nights encourage growth and warmer days discourage growth by moisture loss.…”

Growing Season Stem Water Status Assessment of Qinghai Spruce through the Sap Flow and Stem Radial Variations in the Qilian Mountains of China

“…In fact, Js declined somewhat when ∆W >170 µm, probably due to low soil water content. Root water uptake was limited, resulting in the closure of leaf stomata [45]. The effects of these conditions may lead to the use of tree storage water for transpiration [34,46], and a further increase in ∆W.…”