How a river course influences the species richness and ecological requirements on two opposite riverbanks in a forest area

Abstract

The goal of the present research was to find correlations between the topographic attributes of a river valley and local ground-floor vegetation and its habitat requirements expressed by ecological indicator values (EIV), using the geographical information systems (GIS), digital elevation model (DEM), and multivariate statistical analysis. We paid special attention to the river course, which determines the differentiation in slope aspects and the amount of solar radiation reaching the ground surface. The model object was an almost latitudinal, ca. 4-km-long break section of the Sopot river, crossing the escarpment zone of the Central Roztocze Highlands, southeastern Poland. The main material comprised species lists (with estimated abundance) for each ca. 200-m-long section, according to the river valley course, separately for the left and right riverbanks, 40 sections altogether, ca. 15 000 vegetation records, and physical and chemical soil measurements. A 3-meter resolution DEM was derived from a 1:10 000 topographic map. We calculated the correlations between the topographic attributes of the valley, species richness, and the EIVs for all the species recognized in each section of the valley. We found 241 herb plant species in the ground-floor vegetation of the study area. We did not find significant differences between the two riversides (61 ±13 species per one section for the left and 63 ±17 for the right side). Thus, the parallel course of the river valley does not change the species richness on a more "sunny" and more "shiny" riverbank. However, this factor "cooperating" with other topographic attributes of the valley significantly differentiates the shape of species showing various requirements for basic habitat resources: light, moisture, soil trophy, reaction, dispersion, and organic-matter content.

Topographic attributes and ecological indicator values in assessing the ground-floor vegetation patterns

“…Elevation gradients (denivelations) determine soil variables, vegetation production levels, and patterns of species disturbance (Franklin 1995;Lyon & Sagers 1998;Dorner et al 2002;Pfeffer et al 2003;Fitterer et al 2012). The terrain denivelation of the Sopot river valley expressed as the incision into the substratum (mean = 20 m, max = 27 m) significantly negatively influenced the EIVs for ground-floor vegetation: L, W, Tr, R, D, and H (Czarnecka et al 2015). That attribute was not significant for species richness and ecological variety of the flora in the gorge section of the other river valley, the Szum river, similar in a mountainous character but incised in a bedrock for maximum 15 m (Czarnecka & Chabudziński 2014).…”

“…(1962)1973, secondary pine communities (0.8%). The remaining area (0.5%) is covered by sedge and meadow vegetation (Czarnecka et al 2015). The most valuable gorge part of the valley had been preserved since 1958 in a landscape reserve called 'Czartowe Pole' ('The Devil's Field').…”

“…To estimate the real habitat conditions in the study area and the ecological scale of particular plant species, we also used other field materials: phytosociological relevés in different types of plant communities (60 in total) and soil pits (27 in total; 140 samples of mineral and organic formations) distributed proportionally to the community area, and the diversity of the identified communities. Using commonly accepted methods, soil dispersion (=granulometry) and soil types, as well as basic physico-chemical properties of soil formations, namely the content of organic matter/ organic carbon, active acidity, calcium carbonate, basic nutrients -Ca, K, Na, Mg, Fe, P, and N in the form of ammonia and nitrate, were determined (Czarnecka et al , 2015B. Czarnecka, unpbl.…”

“…in local sites or single patches of plant communities. In natural sciences research, the raster form of the modelthe Digital Elevation Model (DEM) or, less frequently, the Digital Terrain Model (DTM) are used (Moore et al 1991;Tappeiner et al 1998;Pfeffer et al 2003;Feldmeyer-Christe et al 2007; Kopecký & Čižkova Explanations: L1-L20 -left-side sections of the valley, R1-R20 -right-side sections of the valley 2010; Mendas 2010;Fitterer et al 2012;Czarnecka & Chabudziński 2014;Czarnecka et al 2015). Two groups of topographic attributes calculated from the DEM (Wilson & Gallant 2000;Kraak & Ormeling 2003;Evans et al 2014): primary topographic attributes -slope, aspect, planar (or contour), vertical (or profile), and total curvature; and secondary topographic attributes -solar radiation (SRAD) and topographic wetness index (TWI) provide the basis of analytical procedures.…”

“…Over the last decades, the EIV system was widely used, together with the DEMs and multivariate ordination analyses (MOAs), to study relationships between topographic characters and ecological features of different landscapes, including species occurrence and vegetation diversity (Lyon & Sagers 1998;Tappeiner et al 1998;van Dobben et al 1999;Wilson et al 2001;Pfeffer et al 2003;Seidling 2005;Bergès et al 2006;Petřik & Wild 2006;Jolley et al 2010;Angiolini et al 2011;Czarnecka & Chabudziński 2011, 2014Czarnecka et al 2015).…”