Beskydy, 2010, 3 (1): 19–26 © Mendelova univerzita v Brně ISSN: 1803-2451 The decline of Norway spruce Picea abies (L.) Karst. stands in Beskid Śląski and Żywiecki: theoretical concept and reality W. Grodzki Doc. Dr. hab. Wojciech Grodzki, Forest Research Institute, Department of Forest Management in Mountain Regions, ul. Fredry 39, 30-605 Kraków, Poland, e-mail: W.Grodzki@ibles.waw.pl Abstract: Grodzki, W. 2010: The decline of Norway spruce Picea abies (L.) Karst. stands in Beskid Śląski and Żywiecki: theoretical concept and reality. – Beskydy, 3 (1): 19–26 From 2003 the Norway spruce decline started in the Beskid Śląski and Żywiecki (western edge of the Carpathians). The attempt to formalize this process using the Manion’s spiral forest decline concept is presented in the paper. The selected characteristics of stands (species composition, age) and the Armillaria sp. root rot are identified as predisposing factors, the climatic drivers – as inciting and contributing factors, and among the latter ones – also the wind damage and stress to trees are considered. The main contributing factor that determines the spruce decline are bark beetles, which outbreak is shortly characterized in spatio-temporal dimension. The relation of the described real decline process to the spiral forest decline concept is discussed. Keywords: forest decline, spiral decline concept, Picea abies, western Carpathians Introduction ing, respond to the above described schematic model. This paper is an attempt to identify the factors belonging to three above mentioned groups, in relation to the spatio-temporal patterns of this process development, which were already described more in details in specific earlier papers (Grodzki 2007a, 2009a, 2009b) and are only recalled in the current one using the example data from another Forest District located in the area of interest. Decline is defined as chronic malfunction and deterioration leading to death of trees or stands of trees, in contrast to dieback, which is considered as loss of leaves and death of shoots in reaction to acute stress (Jurskis 2006). In case of Norway spruce in Beskid Śląski and Żywiecki one can talk about the decline, as the death of trees and stands occurs on large continuous areas and leads to its deforestation (Grodzki 2009a, 2009b). The tree decline concept, developed by Manion (1991), is illustrated by a decline spiral constituted of three tiered inward rings, corresponding to the predisposing, inciting, and contributing stressing factors, respectively. These three groups represent complex decline syndroms involving a variety of etiological agents, including biotic and abiotic factors (Jurskis 2006). The decline is induced by the sequential occurrence of one stressing factor from each ring, factors within each ring being interchangeable (Desprez-Lousteau et al. 2006). The Norway spruce decline in Beskid Śląski and Żywiecki, started in 2003 and still ongo- Description of study area The data presented in the paper concerns the area of Beskid Śląski and Żywiecki, located at the western edge of the Carpathians and representing a surface of about 1800 km2. The forestry administration in this territory is organized as 8 Forest Districts: Andrychów, Bielsko, Jeleśnia, Sucha, Ujsoły, Ustroń Węgierska Górka and Wisła, which extend on the whole area of interest and a little on the neighboring mountain and upland areas. The forest cover about 84 thous. ha, of which 63% is owned by State and the remaining 37% are private. The dominating 19 20 W. Grodzki species is Norway spruce Picea abies (L.) Karst. (72% in average), the broadleaved trees (nearly 22%) are represented mainly by beech Fagus sylvatica L. (17%). Silver fir Abies alba Mill. and Scots pine Pinus sylvestris L. are not common (about 3% each), the others are present only occasionally. Four Forest Districts: Bielsko, Wisła, Węgierska Górka i Ustroń are subjected to special, pro-ecological forest management as the Forest Promotional Complex “Forests of Silesian Beskid” of a surface of 39780 ha. Material and Methods The results presented in this paper are based on the analysis of data taken from several sources. The general characteristics of stands in the context of bark beetle outbreak were described using the data on forest resources, published by the state forests (Anonym 2007). The data on the extent of the root fungal diseases and wind damage, assessed yearly by the State Forests administration and supplied to the Forest Research Institute for forecasting purposes, were taken from the database kept at the Department of Forest Management in Mountain Regions, Forest Research Institute in Kraków. The meteorological data presented in this paper are taken from the monthly bulletins published by the Institute of Meteorology and Water Management (IMGW) in Warsaw. The data from two stations were used: Katowice (the nearest to Beskid Śląski and Żywiecki) and Zakopane (more distanced but better reflecting conditions in the mountains). The data on the sanitary felling, used for the definition of spatio-temporal patterns of the forest decline, were taken from SILP – the computer system of the State Forests. The analysis was done on two spatial levels: for the area of Beskid Śląski and Żywiecki (about 50 000 ha, resolution: forest compartments) – in order to depict the process dynamics, and for the Forest District Węgierska Górka (about 9000 ha of state owned stands, resolution: forest subcompartments), situated in the core part of the area in both Beskid Śląski and Żywiecki – to depict the altitudinal aspect of spruce decline. In the first case the data from 1980 forest compartments, in the second – from 1740 forest subcompartments, were used. The data on the intensity of sanitary felling (including the processing of trees infested by bark beetles) in individual compartments/subcompartments (respectively) were recalculated to the volume per ha and classified according to the bark beetle frequency: normal (0–0.4 m3.ha−1), premonitory (0.41– 1.2 m3 . ha−1), high (1.21–2.4 m3 . ha−1), very high (2.41–20 m3 . ha−1) and catastrophic (>20 m3 . ha−1) (Grodzki 2007a, 2007b). Based on the obtained data the total area of forest subcompartments ranked to individual classes was calculated. The data from Forest District Węgierska Górka were grouped in altitudinal zones (below 600, 601–800, 801–1000, above 1000 m a.s.l.) based on the forest inventory data, then the mean volume per 1 ha was calculated for individual years and analyzed according to the altitudinal zones in the years 2003 (beginning of the outbreak) and 2008 (culmination year). For the data processing standard Microso Office (MS Excel, MS Access) so ware was used and the statistical treatment was done using Statistica 6.0 (Statso Inc.). Results Predisposing factors: The stand characteristics, especially regarding the spruce as the only tree species affected by the forest decline, should be considered as the main predisposing factor in this process in Beskid Śląski and Żywiecki. The share of Norway spruce in the region (i.e. the territory of 8 previously listed Forest Districts) is about 57%, but in some of them – above 90% (Tab. 1). In the total area of Norway spruce stands the share of those older than 100 years is 32%, but in some cases – much higher (Tab. 1). The vitality and health of Norway spruce, which remains in close relation with the stress caused by Armillaria sp. root rot, is supposed to be the second predisposing factor. The occurrence of the disease concerns more than ⅓ of the area of 8 Forest Districts in Beskid Śląski and Żywiecki, reaching about a half in some units (Tab. 2). During the last decades the area of stands affected by Armillaria sp. root rot increased and the disease has spread towards higher locations, up to the altitudes of about 1 000 m a.s.l. The reduced vitality of Norway spruce results in its low resistance to bark beetle attacks in favorable environmental conditions. Inciting factors Climatic drivers have to be considered as main inciting factor in the spruce decline process in Beskid Śląski and Żywiecki. First of them was the physiological drought which occurred in the spring 2003, as the consequence of snow cover fallen on already frozen soil in late autumn of preceding year, therefore the water inside became inaccessible for trees at the be- 21 The decline of Norway spruce Picea abies (L.) Karst. stands in Beskid Śląski and Żywiecki Tab. 1: The share of Norway spruce and the share of stands older than 100 years in 8 Forest Districts in Beskid Śląski and Żywiecki (source: Anonym 2007) Forest District Forest area (ha) Norway spruce N. spruce >100 years old (ha) (%) 1 (ha) (%)2 Andrychów 11547 1617 14,0 367 22,7 Bielsko 9683 3770 38,9 1330 35,3 Jeleśnia 11330 6786 59,9 2030 29,9 Sucha 10236 3069 30,0 1004 32,7 Ujsoły 13056 12080 92,5 4041 33,5 Ustroń 10879 5140 47,2 2416 47,0 Węgierska Górka 9024 7489 83,0 2308 30,8 Wisła 8395 7922 94,4 1824 23,0 Total 84150 47873 56,9 15320 32,0 in total forest area 2 in the area of Norway spruce stands 1 Tab. 2: Maximum extent of stands affected by Armillaria sp. root rot in the years 2005–2009 in 8 Forest Districts in Beskid Śląski and Żywiecki, according to the yearly reports of the forestry administration Forest District Forest area (ha) Reported occurrence of Armillaria sp. root rot (ha) (%) Andrychów 11547 344 3,0 Bielsko 9683 2694 27,8 Jeleśnia 11330 5154 45,5 Sucha 10236 723 7,1 Ujsoły 13056 87701 67,2 Ustroń 10879 5200 47,8 Węgierska Górka 9024 4520 50,1 Wisła 8395 1326 15,8 Total 84150 28731 34,1 1 together with Heterobasidion annosum ginning of their vegetation. The resulting stress negatively affected the resistance of trees and favored its colonization by the offspring bark beetles. The second one was hot and dry vegetation period in 2003, when high temperatures occurred already during the spring swarming of beetles (Fig. 1a) and lasted above multi-year average in the whole period May–September (Fig. 1c), together with relatively low precipitations (Fig. 1d), as it is evident in both Katowice and Zakopane stations. Contributing factors The first (in temporal sequence) supposed factor contributing to the forest decline was the effect of the wind damage, which affected the spruce stands in November 2004. As the broken and fallen trees were inaccessible for quite long time due to abundant snow cover, the wood was processed in 2005 with a delay in respect to the needs of forest protection (in some areas the processing was started in May). The new damage which occurred in late 2006 was processed in 2007 (Fig. 2). The big amount of fresh spruce logs enhanced breeding conditions for the bark beetles, even if a considerable part of this material was used for natural trapping. The second factor contributing to the decline process is the weather – i.e. extremely hot and dry summers in 2006 and 2007. In 2006 the mean temperature in July was markedly above multiyear average (Fig. 1b), in 2007 such phenomenon occurred in May (Fig. 1a). In both years also the mean temperature in the period May–September was above multi-year average (Fig. 1c), and the summer in 2006 was relatively poor in 22 W. Grodzki °C V °C 20 20 15 15 10 10 5 5 0 0 2003 a VII °C 2004 2005 2006 2007 2008 Katowice Zakopane mean Katowice mean Zakopane 2003 b V-IX 20 900 mm 2004 2005 2006 2007 Katowice Zakopane mean Katowice mean Zakopane 2008 V-IX 800 700 15 600 500 10 400 300 5 200 100 0 0 c 2003 2004 2005 2006 2007 2008 d 2003 2004 2005 2006 2007 2008 Fig. 1: Mean air temperatures (°C) in May (a), July (b) and in the period May–September (c), and the sums of precipitations in the period May–September (d) in the years 2003–2008 on the meteorological stations Katowice and Zakopane (source: IMGW, Warsaw) precipitations in the mountains (Fig. 1d). The action of climatic conditions had the effect on both bark beetle populations (faster development of generations) and the stress in the trees affected by Armillaria sp. disease (further decrease in its resistance against bark beetle attacks). The permanent stress of spruce trees affected by spreading Armillaria sp. root rot, and extended bark beetle outbreak, should then be 400 considered as the third main factor contributing to the forest decline, however the infestations of trees by bark beetles are the main factor finally determining Norway spruce mortality. Spatio-temporal patterns of the spruce decline in the Forest District Węgierska Górka The decline of spruce stands, resulting in fast increase of salvage cuttings, has started already thous. m3 300 200 100 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 Fig. 2: Volume of processed windblown and windthrown trees in the period 2000–2008 in 8 Forest Districts in Beskid Śląski and Żywiecki (line – average 2000–2008) The decline of Norway spruce Picea abies (L.) Karst. stands in Beskid Śląski and Żywiecki in 2002, when fast increase in the tree mortality due to bark beetle infestations was recorded throughout the entire area, particularly in Beskid Żywiecki. In 2003 the bark beetle occurrence level assessed as catastrophic (more than 20 m3 . ha−1) was recorded on 1,6% of the area (about 800 ha), while in 2007 already on 30% (14.6 thous. ha); at the same time the area of stands with bark beetle occurrence assessed as “normal” (<0,4 m3 . ha−1) continuously decreased (Fig. 3). 18000 23 ing into account high share of Norway spruce in the stands (up to more than 90%) and the percentage of stands in the age exceeding 100 years, the probability of a bark beetle outbreak should there be assessed as extremely high (Netherer, Nopp-Mayr 2005). The trees attacked by Armillaria sp. were permanently stressed, but the direct effect of this stress in the period in concern was depending on the temperatures and water resources. In comparison to the status described in 1980-ties the area of the highest [ha] 16000 14000 12000 10000 8000 6000 4000 2000 0 2003 2004 2005 infested trees (m3.ha-1): 2006 <0,4 2007 2008 >20 Fig. 3: Area of stands with normal (below 0,4 m . ha ) and catastrophic (above 20 m3 . ha−1 yearly) level of bark beetle related tree mortality in Beskid Śląski and Żywiecki in 2003–2008 3 −1 The range of bark beetle attacked stands increased towards higher altitudes, including the zone above 1000 m a.s.l. (Fig. 4). If in 2003 the bark beetle caused tree mortality was the highest in the lowest zone and decreased with the altitude, in 2008 it was the opposite – the mortality was the highest in the most elevated zones (Fig. 4). Nevertheless, in 2008 the tree mortality started to decrease and first symptoms of the outbreak collapse appeared in the stands that were attacked first. Discussion It seems that the Norway spruce decline in Beskid Śląski and Żywiecki can be perfectly described using the spiral disease concept based on the action of the three main groups of driving factors. The forests in this area were predisposed for a long time to this process, which eruption was only a question of favorable conditions. Tak- threat by fungal pathogens has moved southwards, to the stands that were relatively healthy and free from the pathogen, including higher altitudinal zones. If in the middle of 1980-ties the area of stands affected by the pathogen was estimated on about 15000 ha (Capecki 1994), the area of such stands at present is about 28.7 thous. ha (Tab. 2), i.e. almost twice as large as 25 years before. As drought has very o en been considered as an inciting factor, and pathogens such as Armillaria sp. as contributing factors (Desprez Lousteau et al. 2006), it seems that in case of spruce decline in Beskid Śląski and Żywiecki the root diseases should be considered also as predisposing factor, due to its long continuous effect on tree vitality, which facilitated bark beetle attacks (cf. Capecki 1994, Jakuš 1998, 2001). The decline started a er the direct action of inciting factors: water shortage together with high temperatures and the wind damage. Spring weather can have direct effects on I. typographus 24 W. Grodzki Fig. 4: Tree mortality due to bark beetle infestation in the altitudinal zones in Węgierska Górka Forest District in 2003 and 2008 propagation and dynamics even more than indirect physiological effects through the host trees (Christiansen, Bakke 1996). Favorable thermal conditions and abundant breeding material in form of wind broken and fallen, as well as standing – stressed trees, favored the development of subsequent generations of I. typographus, which resulted in a dynamic outbreak (Grodzki 2007a, 2009b). In 2003, when the spruce decline was just starting, it was predicted that this process will continue in Beskid Śląski and Żywiecki, and can develop eastwards to the spruce stands affected by root diseases (Grodzki 2004), which came true in the next years. Wind damage should be perceived also as a factor contributing in the spruce decline: windblown trees are always used by the bark beetles as easily accessible breeding material, which enables fast reproduction. Even if the fallen and broken trees were used by the foresters as natural traps in 2005 (which resulted in slight and temporal decrease in the mortality of standing trees), the amount of fresh, not timely processed trees contributed in the develop- The decline of Norway spruce Picea abies (L.) Karst. stands in Beskid Śląski and Żywiecki ment of the bark beetle outbreak. According to the pattern described from the other mountain areas in Poland (Grodzki et al. 2007) and Europe (Forster 1998; Göthlin, Schroeder 2000), the effect of wind damage on bark beetle populations occurs in the second growing season a er the disaster. The facts from Beskid Śląski and Żywiecki confirm that climatic extremes can accelerate chronic declines associated with human management (Jurskis 2006). The main biotic factor driving the spatial development of the spruce decline process was the colonization by Armillaria sp., as the disease spread from the northern part of the area (lower altitudes in Beskid Śląski) southwards, to Beskid Żywiecki, up to the altitude of 1100 m a.s.l. (Żółciak et al. 2009). The same vertical pattern (from valleys towards upper mountain zone) concerns the development of the bark beetle related spruce mortality, presented in this paper based on the data from the Forest District Węgierska Górka (located in both Beskid Śląski and Żywiecki), but already described as similar from the neighboring Forest District Ujsoły, entirely located on Beskid Żywiecki (Grodzki 2009b). Even if the conditions on higher altitudes are not favorable for the development of bark beetles, the key species Ips typographus usually has two main generations even on the altitudes around 1000 m a.s.l. (Grodzki 2007b). Therefore, one can distinguish two types of the spruce decline in mountain areas: from the crests downwards (Sudety, the 1980-ties), and bottom-up from the valleys (presently in Beskidy), related mainly to the predisposing factors (air pollution and insect defoliation in the Sudety vs. Armillaria sp. root rot in the Beskid Śląski and Żywiecki), but also resulting in different effects in the for- References A NONYM 2007: Wyniki aktualizacji stanu powierzchni leśnej i zasobów drzewnych w Lasach Państwowych na dzień 1 stycznia 2007 r. Biuro Urządzania Lasu i Geodezji Leśnej, Warszawa, 54 pp. CAPECKI, Z. 1994. Rejony zdrowotności lasów zachodniej części Karpat. [Forest health condition regions in the western Carpathians]. Prace Instytutu Badawczego Leśnictwa, seria A, 781: 61–125. CHRISTIANSEN, E., BAKKE, A., 1996: Does drought really enhance Ips typographus epidemics? A Scandinavian perspective. In: GRÉGOIRE, J.-C., L IEBHOLD, A.M., STEPHEN, F.M., DAY, 25 est ecosystems (Grodzki 2009a). 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