Climate Warming and Drought in the Bialowieza Forest from 1950–2015 and Their Impact on the Dieback of Norway Spruce Stands

Andrzej Boczoń,Karol Sokołowski,Marek Ksepko,Anna Kowalska

doi:10.3390/w10111502

Abstract

The Bialowieza Primeval Forest (BF) is one of the well-known forests in Central Europe. The most common tree species in BF was Norway spruce (Picea abies (L.) H. Karst), comprising 26%. However, a mass dieback of spruce has occurred during recent years. The spruce dieback in Bialowieza Forest is directly caused by the spruce bark beetle. However, the mass appearance of this pest can be a consequence of global warming and drought. Changes in air temperature were presented and drought indices were calculated as follows: standardized precipitation index, Palmer drought severity index, climatic water balance and soil water storage deficit. The warming of the climate of Bialowieza from 1950 to 2015 is comparable to that observed throughout central Europe. The temperature increased by 1.27 °C. The occurrence of drought from 1950 to 1966 and from 1985 to 2015 had a similar frequency. From 1963 to 1966, the volume of removed deadwood from the managed part of Bialowieza Forest was 27 thousand m3 but from 2012 to 2016, the volume was more than one million m3.

Highlights

The occurrence of long, rainless periods in 1997 and 2000 in Bialowieza Forest was previously indicated by [1] and the drought in 2000 caused a significant reduction in the groundwater level [2], which could have posed a serious threat to tree health
The question arises whether the climate of Bialowieza Forest has warmed up, influencing habitat conditions that caused the spruces to weaken, thereby increasing their susceptibility to attack by the spruce bark beetle in recent years
From 1950 to 2015, Bialowieza Forest experienced climate warming comparable to changes observed throughout the Northern Hemisphere

Summary

Introduction

The occurrence of long, rainless periods (over 28 days) in 1997 and 2000 in Bialowieza Forest was previously indicated by [1] and the drought in 2000 caused a significant reduction in the groundwater level [2], which could have posed a serious threat to tree health. A spruce bark beetle outbreak has recently caused a massive dieback of spruce in the Bialowieza. The question arises whether the climate of Bialowieza Forest has warmed up, influencing habitat conditions that caused the spruces to weaken, thereby increasing their susceptibility to attack by the spruce bark beetle in recent years. Norway spruce is a boreal species; it is cold-adapted but drought-sensitive [7,8]. This species is highly vulnerable to the increasing frequency and severity of drought events associated with recent climate change [9]. Allen et al [11], as well as Birdsey and Pan [12], observed an increase in tree mortality as a consequence of drought and warm temperature in forests

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