Open AccessDefoliation and dieback of Sitka spruce in Reykjavík, Iceland
Author(s) -
Juliane Kuckuk,
Sibren van Manen,
Ólafur Eggertsson,
Edda Sigurdís Oddsdóttir,
Jan Esper
Publication year - 2021
Publication title -
icelandic agricultural sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.187
H-Index - 10
eISSN - 2298-786X
pISSN - 1670-567X
DOI - 10.16886/ias.2021.02
Subject(s) - aphid , overwintering , pest analysis , outbreak , population , biology , agronomy , horticulture , forestry , botany , environmental science , geography , demography , virology , sociology
The green spruce aphid Elatobium abietinum is an important defoliating pest of Sitka spruce (Picea sitchensis) in Iceland. A comparison of two urban Sitka stands in Reykjavík, from 2013-2017, reveals a distinct defoliation difference between trees located near a main road (94% defoliated) and several hundred meters away from heavy traffic (47%). Chemical analyses of the spruce needles demonstrate substantially higher nitrogen ratios in trees near traffic. Furthermore, the recently warming winter temperatures promoted larger overwintering aphid populations since 2003, as well as a shift of mass outbreaks from autumn to spring, accompanied by distinct growth suppressions one year after an aphid population spike in the post-2003 tree-ring data. The results of this study indicate that the mechanisms triggering Sitka spruce dieback in Reykjavík include a combination of increasing winter temperatures, more frequent and severe green spruce aphid outbreaks, as well as elevated N values in the needles of urban trees.