Defining an adequate sample of earlywood vessels for retrospective injury detection in diffuse-porous species.

Estelle Arbellay,Markus Stoffel,Christophe Corona,Patrick Fonti,Armelle Decaulne

doi:10.1371/journal.pone.0038824

Abstract

Vessels of broad-leaved trees have been analyzed to study how trees deal with various environmental factors. Cambial injury, in particular, has been reported to induce the formation of narrower conduits. Yet, little or no effort has been devoted to the elaboration of vessel sampling strategies for retrospective injury detection based on vessel lumen size reduction. To fill this methodological gap, four wounded individuals each of grey alder (Alnus incana (L.) Moench) and downy birch (Betula pubescens Ehrh.) were harvested in an avalanche path. Earlywood vessel lumina were measured and compared for each tree between the injury ring built during the growing season following wounding and the control ring laid down the previous year. Measurements were performed along a 10 mm wide radial strip, located directly next to the injury. Specifically, this study aimed at (i) investigating the intra-annual duration and local extension of vessel narrowing close to the wound margin and (ii) identifying an adequate sample of earlywood vessels (number and intra-ring location of cells) attesting to cambial injury. Based on the results of this study, we recommend analyzing at least 30 vessels in each ring. Within the 10 mm wide segment of the injury ring, wound-induced reduction in vessel lumen size did not fade with increasing radial and tangential distances, but we nevertheless advise favoring early earlywood vessels located closest to the injury. These findings, derived from two species widespread across subarctic, mountainous, and temperate regions, will assist retrospective injury detection in Alnus, Betula, and other diffuse-porous species as well as future related research on hydraulic implications after wounding.

Highlights

Tree-ring studies have only recently started to take advantage of the development of automatic image analysis systems, which have enabled extensive examination of xylem cells across series of annual rings with the aim of better comprehending the effects of external factors on tree growth [1,2]
Cambial injury caused average vessel lumen area (AVLA) to decrease by 61% in Betula I (Table 1), which necessitated the measurement of 9 vessels to identify the disturbance in the injury ring (Figure 2, Early earlywood (EE), P,0.05)
Wound-induced vessel anomalies have been attributed to changes in auxin and ethylene concentrations [28,29,30], and have only recently been employed to date scars inflicted on trees by mass-movement processes [13,16,27,31]

Summary

Introduction

Tree-ring studies have only recently started to take advantage of the development of automatic image analysis systems, which have enabled extensive examination of xylem cells across series of annual rings with the aim of better comprehending the effects of external factors on tree growth [1,2]. Garcıa-Gonzalez and Fonti [8] highlighted the fact that there was no common practice in the sampling procedure of vessels in dendroecological studies and that an adequate sample of cells ought to be established to minimize the risk of missing environmental information. The authors tackled this methodological issue for two ring-porous species, Castanea sativa Mill. Have there been much fewer dendroecological studies conducted with vessels of diffuse-porous species [9,10,11,12,13,14], but the question of ensuring a representative sample of cells has not been addressed yet. Previous measurements of vessels in diffuse-porous wood have been made either on a fixed number of randomly selected cells [11], within a specific portion of the ring (early earlywood [16] or central portion of the ring [17]) or across the entire ring [10,14]

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Conclusion