Influence of selected factors on bark beetle outbreak dynamics in the Western Carpathians

Abstract

In the period from 1992 to 2013, more than 3.8 million m 3 of spruce wood from an area of 55 thousand ha of forests in the Kysuce region (Western Carpathians) was affected by bark beetles. This region has had the highest volume of salvage fellings in Slovakia. While before 1991, bark-beetle outbreak usually occurred after snow and wind disturbances, since 1992 they have occurred in the years with extremely warm and dry growing seasons and the years following them. These years were also characterised by high volumes of wood affected by honey fungus (Armillaria spp.), which only rarely took part in the calamities before 1992. Extreme deterioration of the situation occurred after 2003. In fragmented and sparse stands, the volume of wood damaged by wind increased. Artificial origin of spruce stands, their high occurrence, high age and even-agedness are likely pre-disposing factors of spruce forest decline. Bark beetles have become the most important factor of spruce decline. The most important factors driving the bark beetle attack on forest stands in the period 1973-2013 were the amount of unprocessed wood in the previous year; the amount of wood affected by honey fungus, precipitation total, and average temperature in the current growing season. Another important factor that complicated the situation was also the inferior quality of forest management.Keywords: Ips typographus; spruce decline; regression modelling; weather condition; salvage felling abstrakt V období rokov 1992-2013 bolo v regióne Kysúc (Západné Karpaty) napadnutých podkôrnym hmyzom viac ako 3,8 mil. m 3 smrekového dreva na ploche 55 tis. ha lesa. Tento región patrí dlhodobo k regiónom s najvyšším objemom náhodných ťažieb na Slovensku. Pokiaľ do roku 1991 dochádzalo k premnoženiu podkôrneho hmyzu predovšetkým po snehových a vetrových kalamitách, od roku 1992 dochádza ku vzniku kalamít podkôrneho hmyzu v rokoch s extrémne teplými a suchými vegetačnými sezónami a v rokoch po nich nasledujúcich. Tieto roky sa vyznačujú zároveň vysokým objemom dreva napadnutého podpňovkou, ktorá sa podieľala na kalamitách pred rokom 1992 len zriedkavo. K extrémnemu zhoršeniu situácie dochádza po roku 2003. Vo fragmentovaných a preriedených porastoch dochádza následne k nárastu objemu dreva poškodeného vetrom. Nepôvodnosť smrekových porastov, ich vysoké zastúpenie, vysoký vek a rovnovekosť sú predispozičnými faktormi odumierania smrečín. Podkôrny hmyz sa stal najvýznamnejším činiteľom odumierania smrečín. Faktormi najvýznamnejšie vplývajúcimi na napadnutie porastov podkôrnym hmyzom v období 1973-2013 boli množstvo nespracovaného dreva v predchádzajúcom roku; množstvo dreva napadnutého podpňovkou, úhrn zrážok a priemerná teplota vo vegetačnej sezóne v danom roku. Medzi ďalší faktor, ktorý významne skomplikoval situáciu bola zhoršená kvalita lesníckeho manažmentu.

Range expansion of the small spruce bark beetle Ips amitinus: a newcomer in northern Europe

“…This bark beetle is retracting its wide range in the north of European and Siberian taiga, whereas it is extending southwards from its natural range (Lekander et al , ; Grodzki, ; Vakula et al , ; Holuša et al , ; Olenici et al , ). It is considered to be a newcomer in some parts of Central Europe, where spreading and outbreaks have been observed from the 1990s onward (Vakula et al , ; CABI, ). Ips mannsfeldi (Wachtl, 1879) is distributed on black pine ( Pinus nigra J.F Arnold) and Scots pine ( Pinus sylvestris L.) in Central and South Europe, and this species is expanding its range in Turkey (Sarikaya et al , ).…”

Comprehensive comparison of treatments for controlling the large pine weevil (Hylobius abietis) in Central Europe

“…In these areas, the abundance of stumps and harvest residues provide breeding habitat and food for H. abietis 18 . Wind disturbances are also regularly followed by outbreaks of bark beetles (especially the spruce bark beetle, Ips typographus 52 ), which produce additional material suitable for the development and maintenance of large populations of H. abietis . Damage to seedlings (mainly of spruce) by H. abietis is especially severe in national parks (at elevations up to 1200 m a.s.l., pers.…”

Comprehensive comparison of treatments for controlling the large pine weevil (Hylobius abietis) in Central Europe

“…In these areas, the abundance of stumps and harvest residues provide breeding habitat and food for H. abietis 18 . Wind disturbances are also regularly followed by outbreaks of bark beetles (especially the spruce bark beetle, Ips typographus; 53 ), which produce additional material suitable for the development and maintenance of large populations of H. abietis. Damage to seedlings (mainly of spruce) by H. abietis is especially severe in national parks (at elevations up to 1,200 m a.s.l., pers.…”