Structure and Function of Intra-Annual Density Fluctuations: Mind the Gaps.

Giovanna Battipaglia,Martin De Luis,Alfredo Di Filippo,Achim Bräuning,Cristina Nabais,Nikolay Zafirov,Paolo Cherubini,Alexander V Kirdyanov,Joana Vieira,Veronica De Micco,Marcin Klisz,Marcin Koprowski,Katarina Čufar,Ignacio García-González,Marco Carrer,Michael Grabner,Filipe Campelo

doi:10.3389/fpls.2016.00595

Abstract

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Highlights

Intra-Annual Density Fluctuations (IADFs) have long been considered by dendrochronologists as the “Ugly Duckling” of wood anatomical features, and species forming them have often been discarded for climate reconstructions (Lorimer et al, 1999) and used as indicators of particular events such as flood-regime or air pollution
The lumen area of a tracheid depends on turgor pressure and duration of cell enlargement (Cuny et al, 2014). These results suggest that the formation of latewood IADFs in the Mediterranean area are defined during the enlargement phase, whereas it is possible that latewood IADFs formed at higher altitudes and latitudes are caused by changes in the cell wall deposition phase
This unique and novel catalog includes IADF identification and measurements in 10 countries, 14 species, and 108 tree populations with a total of 2199 trees (3670 cores) and 234,262 tree rings. In this perspective we present a first exploratory analysis on IADFs showing a wide range of variability in IADF frequency (Figure 2, Table S2), with sites where IADFs are nearly absent and others where IADFs are present in most tree rings

Summary

Introduction

There have been recently major developments in this field, leading to a detailed description of the timings of cambial activity, duration of cell production and differentiation phases and response of cambium to environmental conditions in different species and environments (De Luis et al, 2007; Camarero et al, 2010; Cuny et al, 2014). Further studies are needed because a number of different anatomical functional traits seem to work for IADF identification in hardwoods, but they appear to be species-specific (De Micco et al, 2015).

Results

Conclusion