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Structure of Dominance among Tree Species in Relic Swiss Stone Pine (Pinus cembra L.) Forests in Tatra Mountains

Zięba Antoni, Różański Wojciech, Szwagrzyk Jerzy

Polish Journal of Ecology

2020

Vol. 68, nr 2

159--171

Pinus cembra forests are limited to the Alps and Carpathians. Although several studies regarding their structure were carried out in some locations in the Tatra Mts. it required further investigations. Therefore, the aims of this study were to describe the stand and shrub structure of P. cembra forests, compare their structure with the Picea abies forests and analyse differences between silicate and calcicolous P. cembra forests in the Tatra Mts. The data were collected on the 16 sampling plots (500 m2), in the Swiss stone pine and Norway spruce forests. We measured the diameter at breast height (dbh) of each tree and recorded the young trees and shrubs. In order to compare species composition between silicate and calcicolous P. cembra forests, we made 91 relevés in their entire range of distribution (917 ha). Furthermore, we examined the share of main tree species along the altitude and inclination gradients, using the GAM models. The tree density in the P. cembra forests reaches 618 stems per ha, whereas their basal area (BA) 23.17 m2 ha-1. Main tree species are P. cembra and P. abies. P. cembra dominates in the higher thickness classes. The BA and dbh structure varies significantly between P. cembra and P. abies forests. The most abundant juveniles are P. abies and Sorbus aucuparia. The differences between forests growing on different substrate are relatively low. The altitude has a significant impact on the share of P. cembra (increase) and P. abies (decrease). The inclination has a significant impact on the increase of share of P. cembra.

Invertebrate reproduction in astatic water bodies : egg number - body weight relationship in Viviparus viviparus (L.) from oxbow lakes

Jakubik B.

Polish Journal of Ecology

2012

Vol. 60, nr 2

363-374

Reproduction is the most important factor in population dynamics and invading freshwater habitats by Viviparus viviparus. This is largely associated with ovoviviparity of these snails. Some traits like steered reproduction, the appearance of young snails during the whole year, protection of embryos by female and delayed reproduction were fixed by natural selection as adaptations increasing the chance for progeny survival. In variable habitats like oxbow lakes seasonally joined to the river channel, Viviparidae start reproducing in the early stage of their life hence increasing a chance for population to survive. Studies on fecundity, embryonic development of V. viviparus and the relationships between these parameters and females. body size and weight, were carried out in oxbow lakes periodically connected to the river (the Bug River, Central Poland). The Bug River is one of a few European rivers which preserved their nearly natural character. No larger hydrotechnical works have been made in its valley, therefore, the river flows in a natural, meandering channel and forms numerous oxbow lakes. The surrounding of studied oxbow lakes is flat and of lowland character with mixed land use structure (arable lands, grasslands, settlements). Oxbow lakes are fed by the runoff from flood terrace, hence their waters are more fertile than those of the river. Two lakes were selected: Lake Szumin, area 17 ha, Lake Wywłoka - area 23 ha. Maximum depth of both lakes is ca 3 m. Samples of V. viviparus were collected in the years 2003-2007 with a bottom drag during the successive seasons from five sites in each oxbow lake. The embryos were found in females of the II (8.1-12.0 mm of width and height), III (12.1-20.0 mm width and 12.1-25.0 mm height) and IV (over 25.0 mm height and over 20.0 mm width) size classes. Three developmental stages were distinguished in embryonic growth: the oval transparent egg capsules (called the youngest embryos), egg capsules with visible contour of a shell (called medium embryos) and snails with a shell (the oldest embryos). The youngest growth stages of embryos (in a form of oval transparent egg capsules) dominated in all size classes of females. Medium growth stages (egg capsules with visible outlines of the shell) and the oldest ones (with shell) were represented in smaller proportion. The highest number of the youngest embryos per female were found in females of the II size class. The proportions of the embryo growth stages varied seasonally. The number of embryos per female and the degree of their development increased with the increase of shell (height, width, dry weight) and body (dry weight) parameters. High fecundity of the youngest females of V. viviparus is probably an adaptation to unstable habitat conditions of oxbow lakes.