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Landscape-Level Spruce Mortality Patterns and Topographic Forecasters of Bark Beetle Outbreaks in Managed and Unmanaged Forests of the Tatra Mountains

Sproull G. J., Bukowski M., Mcnutt N., Zwijacz-Kozica T., Szwagrzyk J.

Polish Journal of Ecology

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2017

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Vol. 65, nr 1

24--37

EN

Bark beetle outbreaks and tree mortality patterns should be better understood to control outbreak impacts. We investigated landscape-level patterns of Norway spruce mortality caused by Ips typographus outbreaks across three periods from 1999–2012 in Tatra National Park (Poland) using high-resolution aerial orthophotos and satellite imagery. Shifts in tree mortality related to elevation, slope, and solar equinox radiation were analyzed with ANOVAs (Tukey's HSD tests). Boosted regression trees were employed to assess the forecasting effectiveness of these variables related to mortality period. Spruce mortality severity increased significantly across time in both managed and unmanaged forests. Management activities did not effectively reduce spruce mortality severity. Mortality severity increased significantly at higher elevations over time, while slope and radiation trends varied. Elevation and radiation were the best forecasters of mortality period, exhibiting moderate predictive ability. Beetle-induced spruce mortality increased significantly in Tatra National Park from 1999–2012, particularly at high elevations. Management strategies aimed at minimizing spruce mortality have been ineffective.

2

High Reproductive Effort and Low Recruitment Rates of European Beech: Is There a Limit for the Superior Competitor?

Szwagrzyk J., Gratzer G., Stępniewska H., Szewczyk J., Veselinovic B.

Polish Journal of Ecology

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2015

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Vol. 63, nr 2

198--212

EN

European beech is a superior competitor among the trees of Central Europe, often growing in pure stands. We proposed a hypothesis, that once beech has reached dominance in forest community, it's recruitment could become limited due to the gradual accumulation of pathogens attacking seeds and seedlings. We employed data on seed production and germination along with a field experiment to estimate the germination success of beech in two old-growth forests. Beech produced more seeds than the co-occurring coniferous trees, but less than 1% of beechnuts germinated in the next season. In the field experiment, the percentage of decayed beechnuts was 57% in the Carpathians and 61% in the Alps. Most of the dead germinants and decayed beechnuts were infested by fungi. The average number of fungal colonies per one sample in the Carpathians was significantly higher after mast year than one year before, while the differences between the Alps and Carpathians after mast years were statistically not significant. Fungi have been isolated from practically all dead beechnuts and dead germinants. The number of beechnuts per seed trap, the number of germinants around it and the relative number of fungal colonies obtained from plastic boxes placed in the same sample plot were not significantly correlated. The mortality of germinants continued throughout the spring; the number of life germinants in the middle of May amounted to 0.87% of the initial number of beechnuts in the Carpathians and only 0.28% in the Alps. High rates of beechnut and germinant mortality could probably offset the huge reproductive effort of European beech in old-growth stands and limit the possibility to attain absolute dominance by that species. However, our hypothesis that the build-up of fungal pathogens on the forest floor old-growth stands is able to stop the regeneration of beech still needs to be tested using larger data sets.

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Long-term changes in stand composition of natural forest associations on the Roztocze Highlands (Eastern Poland)

Maciejewski Z., Szwagrzyk J.

Polish Journal of Ecology

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2011

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Vol. 59, nr 3

535-549

EN

The purpose of this study was to determine the trends and rates of spontaneous changes in the structure and species composition of natural forests which are composed mostly of tree species growing at the limits of their natural range of distribution. We analyzed the demographic processes in populations of woody species in the years 1968-2005. The investigations were conducted in strictly protected areas in the Roztoczański National Park (The Roztocze Highlands, Eastern Poland) on four 0.5-ha sample plots, established in the 1960s. These plots represented three forest communities: upland fir mixed forest Abietetum polonicum (Ap), Carpathian beech forest Dentario glandulosae.Fagetum (DgF), and pine-oaks mixed forest Querco roboris.Pinetum (QrP)). Measurements were conducted in 1968, 1978 (two sample plots only) and in two study periods (1993-1995 and 2003-2005). Measurements in the last two periods included canopy trees (DBH and height) forest regeneration (saplings, seedlings and germinants) as well as dead wood (snags and coarse woody debris). The results revealed significant and dynamic changes in the studied forests. The directions and rates of changes were different among forest communities. Silver fir (Abies alba Mill.) showed continuous decrease in all the forest associations. The highest rates of change were found in the DgF forest association. Data from the last measurement showed, that the rate of fir decline has slowed down, and in some cases even a slight increase of its share was recorded. However, the continuous decrease in abundance of the fir regeneration in all study plots suggests, that fir in the near future can be partly replaced by the broadleaved species. Among them, European beech (Fagus sylvatica L.) revealed the most dynamic species. It showed a systematic increase of it.s share in stand composition, according to the number of trees and basal area in all investigated plots. The largest increase of this species was recorded in the QrP forest association. Untill 1993 hornbeam (Carpinus betulus L.) developed well in the DgF association, and it also increased in abundance in the Ap association. The last measurements confirmed large increase the number of hornbeams in the DgF association, whereas it's share in stand basal area revealed a weak downward tendency in both associations. After 1993 Norway spruce (Picea abies (L.) H. Karst.) grow only in the Ap forest communities, where its development is rather weak. The share of Norway spruce in forest composition has diminished systematically since 1968. The measurements from 2003 revealed a slight increase of the basal area of spruce and substantial decrease of its regeneration. Other tree species: Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) in the successive measurements showed a systematic decrease of their number, basal area and share in the stand composition. There was also no natural regeneration of these species. Observed changes could be mainly attributed to natural processes of forests development (including natural disturbances) in general and to specific mechanisms of competition in forests composed of tree species growing close to the limits of their natural distribution ranges. In some cases the dynamics of researched species (hornbeam, pine and oak) can be explained as the regeneration processes of ecosystems affected previously by human activities.

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Is natural regeneration of forest a continuous process? A case study of an old-growth forest of the Western Carpathians

Szwagrzyk J., Szewczyk J.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

623-633

EN

Natural regeneration in temperate forests is known to be distributed unevenly, forming dense clumps or patches of young trees confined often to canopy gaps. However, in some studies no significant relationship between the presence of gaps and advanced regeneration was found. The analysis of the relationship between tree stand density and young trees density and growth rates was conducted to check if oldgrowth temperate forests with numerous canopy openings permit development of young trees throughout the forest floor, not only directly under canopy gaps. The study was conducted in an old-growth stand of Fagus sylvatica L., Abies alba Mill. and Picea abies (L.) Karst. in the Babia Góra National Park (Western Carpathians, Poland). The elevation is 940-1010 m a.s.l., slope inclination varies from 2 to 40%, mean annual temperature for that area is 4[degrees]C and annual precipitation amounts to 1300-1400 mm. Stand basal area in the study plot has increased from 38 m[^2] ha[^-1] in 1991 to 40.7 m[^2] ha[^-1] in 2004, and canopy openness has decreased from 15.6% in 1996 to 9.3% in 2003. Saplings were totally dominated by European beech; during 13 years of study sapling density has increased by 50%, along with the sum of sapling heights (from 0.79 m m[^-2] to 1.59 m m[^-2]) and the mean height (from 1.42 m to 2.46 m). The increase in sapling sizes strongly varied among individuals within plot and was only weakly related to the relative light intensities measured at the individual plot level (for sums of diameters t = 0.293, P > 0.05). The development of young generation of trees in the study area seems to support the "medium disturbance" hypothesis, with a non-continuous regeneration triggered by external disturbance, and several tree recruitment episodes during the lifespan of canopy trees.

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Secondary forest succession in abandoned glades of the Pieniny National Park

Bodziarczyk J., Michalcewicz J., Szwagrzyk J.

Polish Journal of Ecology

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1999

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Vol. 47, no 2

175-189

EN

The research was conducted in two abandoned glades in the Pieniny National Park (Western Carpathians), were mapping and measurements of invading trees and shrubs had been made in July 1988. Based on re-measurements carried out in 1995, the role of different woody species in secondary forest succession was evaluated. During seven years between consecutive censuses process of succession in both glades displayed substantial convergence. Sycamore Acer pseudoplatanus L. was the main species invading meadows, followed by the hazel Corylus avellana L. Silver fir Abies alba Mill. was common among seedlings, but less numerous among larger saplings. Both sycamore and silver fir seem to be able to invade dense herbaceous vegetation, but higher growth rates allow sycamore to dominate in the early stage of secondary succession.