The potential for using Larix decidua ring widths in reconstructions of larch budmoth ( Zeiraphera diniana) outbreak history: dendrochronological estimates compared with insect surveys

Abstract

In the Alps, larch (Larix decidua Mill.) forests show periodic discolouration due to larch budmoth (LBM) outbreaks (Zeiraphera diniana Guénée, Lepidoptera: Tortricidae). Tree defoliation causes severe reductions in radial growth, visible in tree rings. This paper aims at reconstructing LBM outbreak history, and critically examining the potential for using dendrochronological data by comparing tree-ring estimates with insect surveys. The occurrence of LBM outbreaks was investigated using 249 cores from larch growing near the timberline in three regions of the French Alps (Briançonnais, Maurienne, and Tarentaise). Years with an abrupt decrease in radial growth (-40%) were considered as negative pointer years reflecting the potential impact of LBM. The comparison with three non-host conifers (Norway spruce, stone and mountain pines) permitted us to distinguish growth reductions in larch due to climatic effects from those due to defoliation by LBM. The dendrochronological data were matched with information reporting conspicuous discolouration in old forestry reports or recovered from systematic field observations. Twenty-two outbreaks are discernible within the period 1800-1983. A peak reduction in larch growth occurred at intervals of 8.86±1.Our objective method based on ring measurements and comparison with non-host trees was compared with qualitative techniques based on the visual detection of conspicuous latewood anomalies. Larch in the Briançonnais (which experiences a continental climate) are infested first, whereas the Tarentaise region exhibits a much weaker impact of LBM. Complete tree recovery was observable 3 years after outbreak peaks.

Human land-use, forest dynamics and tree growth at the treeline in the Western Italian Alps

“…2). The SF larch chronology differs from SF stone pine chronology in its periodic intense decreases in growth, related to outbreaks of Zeiraphera diniana Gn (Lepidoptera), [2,43,47,64]. The Rbar statistic is high for the stone pine chronology, as well as for the larch SF and FL chronologies, highlighting a high percentage of common signal in inter-annual growth variations between individuals (Tab.…”

Temporal variations in English populations of a forest insect pest, the green spruce aphid (Elatobium abietinum), associated with the North Atlantic Oscillation and global warming

“…Franco) growing in British Columbia, Canada and the larch budmoth (Zeiraphera diniana Guénée) defoliation of larch (Larix decidua Mill.) in the French Alps (Rolland et al, 2001). …”

Can we reconstruct deer browsing history and how? Lessons from Gaultheria shallon Pursh

“…We suggest that the repetitive, irregular and partial defoliation by deer also explains the asynchronism observed in stem sections from deer-affected islands, in contrasts to the synchronism observed for sections collected on deer-free islands. Thus identifying, counting and dating abrupt growth changes in salal populations should allow to reconstruct the local history of deer browsing in a way similar to what has been done using adult tree rings [26] to reconstruct the history of insect outbreaks [31,32,42] or scars to reconstruct past caribou activity [33], porcupine expansion [36], beaver occupation [4] or changes in deer population [34,35].…”