High-resolution monitoring of daily stem fluctuations in the long-lived Fitzroya cupressoides

SERRA OLABUENAGA, IGNACIO; VILLALBA, RICARDO; SUAREZ, MARIA LAURA; MAGNIN, AMARU

Mendoza

Conferencia; Third American Dendrochronology Conference; 2016

Tree-Ring society y IANIGLA

Monitoring how a tree?s stem radius varies over minutes to yearscan provide insight into intra-annual stem dynamics and improveour understanding of climate impacts on tree physiology andgrowth processes. We applied high-resolution measurements tostudy stem radial growth of alerce (Fitzroya cuppresoides) inPatagonia, between 2013-2015 using automated pointdendrometers coupled with high-resolution climate monitoring.We extracted out of the daily time series intra-annual dynamicsof stem water deficit (W) and maximum daily shrinkage (MDS).We compared the influence of environmental drivers(temperature, precipitation and soil moisture) by applyingmoving correlation analysis (MCA) and simple response functionanalysis. Daily cycles varied in both timing and amplitudebetween months and seasons. Extracted W and MDS fluctuatedsynchronously among individuals and were negatively (W) andpositively (MDS) correlated with air temperature. Throughoutthe growing season tree stem diameters were greatest at earlymorningand smallest in the afternoon. Stem diameters werevery sensitive to rain events, particularly during dry spells.Seasonal changes in stem diameters show a slow increase by the beginning of fall, compensating for the shrinkage that occurredduring the summer, until reaching a standstill during the winter.The end of cambium dormancy in the beginning of spring leadsto a monotonic steep increase in stem diameter until peaking inearly-summer, after which it decreases due to the increasedwater deficit. In 2014-15 Patagonia had its worst drought eventof the past 20 years. Accordingly, soil water availabilitydecreased drastically and all recorded trees stem diameters alsoabruptly declined. These results may reflect only the mechanicalaspect of growth and show that it is not a result of a continuousincrease, but it is a sequence of consecutive or alternatingperiods of increase, stagnations, shrinking and swellingdepending on intra-annual weather fluctuations.