The Number and Composition of Snags in the Pine-Spruce Stands of the Bialowieza National Park, Poland

This paper documents data on standing dead trees (snags) in the pine-spruce (Norway spruce Picea abies, Scots pine Pinus sylvestris) natural stand in Bialowieza National Park (BNP) in northeast Poland. Trophically, this mostly coniferous stand represents one of the poorest habitats of the BNP, and this stand has never been cut. There are few tree species of significance, i.e., Scots pine, Norway spruce, hornbeam Carpinus betulus and two birch species Betula verrucosa, B. pubescens. Other tree species are scarce. Altogether 6.25 ha were measured within 25 samples. Among tree species, the proportion of dead standing trees was 0-58 percent of the total basal area and 0.9-59 percent of total density. The tree species dominance pattern shows a different pattern of change. Pine is declining, while hornbeam is invading the stand from bordering deciduous stands and now is a well regenerating tree species. Spruce regeneration slowed within the last 20 years. Until about 10 years ago, birches were not regenerating and were declining from the plot. Recently, within no more than the last 10 years, birches are regenerating within the plot again. All these changes reflect snag characteristics and composition. Introduction Most of the lowland forests of the European temperate zone underwent severe anthropogenic transformations before modern research started. However, the forests of the Bialowieza National Park are an exception. The Bialowieza Forest complex (total area 1,500 km) is situated on the Polish-Belarussian border (fig. 1). Its western part (c. 600 km) belongs to Poland. This forest is a remnant of the vast lowland forest that once covered central parts of Europe. The majority of stands in the Polish part of the forest are now under management, but 47.5 km of the best preserved primeval stands has been protected within the Strict Reserve of the Bialowieza National Park (SR BNP) (Falinski 1986, Tomialojc 1991). This part has never been cut because it was protected as hunting grounds for the Polish kings and later the Russian czars since the early 15th century. After World War I it became the first Polish national park. Human presence is very restricted to some tourist trails only. 1 An abbreviated version of this paper was presented at the Symposium on the Ecology and Management of Dead Wood in Western Forests, November 2-4, 1999, Reno, Nevada. 2 Adjunct Professor/Lecturer, Department of Zoology, University of Podlasie, Prusa 12, 08-110 Siedlce, Poland (e-mail: [email protected]) Snags in the Pine-Spruce Stands of the Bialowieza National Park—Walankiewicz USDA Forest Service Gen. Tech. Rep. PSW-GTR-181. 2002. 490 Figure 1_A map of the Polish part of the Bialowieza Forest showing the location of the strict reserve (SRBNP) and study plot (NW). The old-growth preserved in SR BNP are mainly the linden-hornbeam TilioCarpinetum type (44.4 percent), swampy deciduous (26.6 percent), and dry coniferous (28.1 percent) stands. The old-growth stands of SR BNP are multi-storey, mixed-species, uneven-aged, composed of trees reaching exceptional height, and contain large amount of dead standing trees (snags) and uprooted trees. In spite of the fact that many authors stressed the high amount and the importance of the dead wood in this forest, the quantitive data are scarce and only general (Falinski and Herezniak 1977, Kirby and others 1991, Piotrowski and Wolk 1975). Although most of the SR BNP is covered by deciduous woodland, the coniferous stands (i.e., pine-spruce stands [Norway spruce Picea abies, Scots pine Pinus sylvestris]) contribute greatly to sustaining biological richness of BNP. For instance, several bird species are recorded mostly or exclusively in this conferous habitat (Tomialojc and others 1984). Structure and dynamics of the BNP natural stands have been studied for almost 80 years (Falinski 1986, Paczoski 1925). Both deciduous and coniferous stands of SR BNP are not in a state of climax. In the linden-hornbeam Tilio-Carpinetum type, the spruce has decreased steadily in number (Falinski 1986). In coniferous forests, i.e. pine-spruce type, the pine share has decreased as well. Comparing tree distribution maps from 1903 and 1958, Czerwinski (1968) stated that during the investigated period, pine decreased substantially and it was replaced by the spruce and oak Quercus robur. Wloczewski (1972) and Kowalski (1972) also noticed directional change of the pine stands into the spruce stands. Even more, an increase of the hornbeam Carpinus betulus in number in coniferous stands has been noticed (Gunia 1972; Kowalski 1972, 1982). Snags in the Pine-Spruce Stands of the Bialowieza National Park—Walankiewicz USDA Forest Service Gen. Tech. Rep. PSW-GTR-181. 2002. 491 This study aims to describe the occurrence and characteristics of the snags (i.e., dead standing trees) within the pine-spruce stands of the SR BNP under the dynamic process ongoing in this stand with time. Snag characteristics have never been described in details in these forests, and only Jakubowska-Gabara and others (1991) have assessed how many dead standing trees were among all trees in the same type of stand of BNP. Study Plot The NW 25-ha study plot (500 m x 500 m, located in compartment 318A; Tomialojc and others 1984) was chosen. It is covered by the pine-spruce natural stand, which has never been cut. The association of this kind usually develops on sandy soils in upper parts of the BNP. Trophically, it represents one of the poorest habitats in SR BNP. The main canopy is formed of pines, while the lower one is composed of spruces with few pines, birches (Betula verrucosa, B. pubescens), and oak. In the plot, spruce dominates numerically over pine. The young tree-layer is composed mostly of hornbeams and spruces. The herb layer is sparse, composed of Oxallis acetosella and Vaccinium myrtillus. Forest openings are dominated by Calamagrostis arundinacea and Pteridium aquilinum. The plot has been subdivided into a 50-m grid. That area has been under ornithological investigation since 1975 (Tomialojc and others 1984). Since that time an increase of hornbeam in number is very visible. The young generation of Carpinus betulus invades the area from the north and especially from the south, i.e., from the transition border zones with the deciduous stands. This transition, where coniferous stands turn gradually into deciduous stands, is 50-80 m wide. Matuszkiewicz and Matuszkiewicz (1954) mapped the whole study plot as the pine forest Pinetum Myrtylli association. Methods In June and July 1998 I counted and measured the diameter at breast height (dbh) of all trees that reached at least 1.5 m tall within the 50 m x 50 m squares (samples). One such square (0.25 ha each) was chosen randomly within every ha of the study plot (fig. 2). Altogether 6.25 ha were measured within 25 square samples. Both live and dead trees were identified to species. The recognition of dead trees caused no serious problems, since there were only two coniferous and a few deciduous species. The exception is the two birch species, which I treat jointly since they were uncommon and I was unable to distinguish snags of those species. Additionally, to illustrate the hornbeam invasion in the northwest plot, I compared the diameter distribution within the central part of the plot with that of the ecotonal (southern) part of the plot. For this, five samples were chosen in both parts (fig. 2). Snags in the Pine-Spruce Stands of the Bialowieza National Park—Walankiewicz USDA Forest Service Gen. Tech. Rep. PSW-GTR-181. 2002. 492 1 2 3 4 5 6 7 8 9 10 A