Herb Layer Diversity and Phytoindicative Evaluation of Habitat Conditions of Forest Permanent Plots in Poland

The influence of climatic and pollution gradients was determined on species richness, species diversity, and values of phytoindicators of the herb layer in pine and mixed pine forest communities in Poland. Geographical longitude was used as a synthetic measure of geographical position. Ellenberg’s indices were used as synthetic measures of habitat differentiation, calculated as weighed averages: L (light index), T (temperature index), K (continentality index), F (moisture index), R (reaction index), N (nitrogen index). Richness and diversity variables were used: razem (total number of species), gatB (number of shrub species), gatC (number of herb layer species), diver (Shannon’s diversity index H = -∑plogp), simps (Simpson’s index S =∑p2), beta (beta =[1simps]/[1-1/gatC]). Additional dependent variables included the proportion of number and cover of different Raunkiaer’s life forms as well as shares of number and cover of species of different leaf anatomy and different syntaxonomic character. By using Ellenberg’s indices the vegetation on consecutive sample plots was not strongly differentiated. All sites on the climatic transect occurred on dry, strongly acidic or acidic soil, with low nitrogen content. Values for the index of continentality “K” reflected clearly the climatic differentiation from west to east. The number of herb layer species depended on the geographical longitude (correlation coefficient 0.851) for pine and mixed forests together, 0.840 for pine forests only, and 0.926 for mixed forests only. All diversity indices were also strongly correlated with the longitude. Generally, the share of the number of chamaephytes and therophytes was positively correlated with the longitude. In pine forests there was also a general tendency for the number of scleromorphic species to decrease (and mesomorphic species to increase) in the west-east direction. Meadow species also generally tended to increase in the west-east direction. For all the plots taken together the cover of meadow species is correlated with the longitude (correlation coefficient 0.881), 0.905 for pine forests only, and 0.910 for mixed forests. Introduction Species richness and species diversity are some of the most important structural features of forest communities. They are influenced by a range of factors such as large-scale geography and habitat (Cowling 1990, Day and others 1988, Grime 1979, Jurko 1985, Prusinkiewicz 1970). Other important factors are the history of vegetation development in the Holocene (Huntley 1993) and the history of use (Law and Morton 1993) to interpopulational and successional interactions (Dollar and others 1992, Trevin and others 1993). The role of the different factors changes in relation to the scale of the phenomenon considered. In analyses on a scale larger than the region, overall geographical factors, including macroclimatic differentiation, are most important. Macroclimatic differentiation consists of many elements, including mean annual temperature, total precipitation, moisture deficit, the amplitude of annual temperatures, the degree of continentality of the climate and the length of the growing season. These elements are mutually interlinked and are dependent on geographical location. It is for this reason also that many studies consider the link between structural features of the flora and vegetation and geographical location, treating the latter as a synthetic indicator of macroclimatic differentiation. This paper defines the relationships between geographical location (which determines macroclimatic differentiation and reflects the history of development of the vegetation), habitat conditions (Ellenberg 1974), and selected characteristics of the species richness and diversity of the ground cover in two narrowly-defined types of forest community, namely, within typical pine forests and within mixed Herb Layer Diversity and Phytoindicative Evaluation of Habitat Conditions of Forest Permanent Plots in Poland1 1 An abbreviated version of this paper was presented at the International Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems, February 5-9, 1996, Riverside, California. 2 Botanists, Institute of Geography and Spatial Organization, Polish Academy of Sciences, 00-927 Warsaw, Krakowskie Przedmiescie 30, Poland.