Influence of some ecological factors and forest practice on the spatial pattern of species richness and distribution of lowland forests at landscape level (a case study: Floodplain forest area of Ravni Srem, Serbia)

Abstract

© By PSP Voume 23 - No 9a. 2014. During the floristic studies of lowland forests of Ravni Srem, performed in order to determine the diversity of vascular flora in this area, the relevant ecological factors were monitored as the base for ecological gradient analysis. Canonical Corrsespodene Analysis was used to explore patterns of variation in Pedunculate Oak forests distribution. Analysis of Similarities-ANOSIM was used in order to explore the relationship between species richness and determined ecological variables, as well as different practice of forestry management. The resulting geospatial distribution of species richness in lowlannd forests, in relationship to the studied hydrological gradient and various intensities of forestry management treatments (comprising thinning processes), has shown a statistically significant difference in the number of recorded taxa per analyzed UTM square in different localities of flooded and non-flooded area. This result confirmed that species richness enlarged with increasing water availability. The result of geospatial analysis of species richness indicates that flooding duration strongly affects species richness. The highest values of species richness were recorded in the intermediary zone of hydrological gradient. This indicates that the pattern of species richness in Ravni Srem originally increases with the duration of flooding (the highest in the range of 60 to 70 days of inundation), after which gradually decreased with the increasing of the gradient Also, the greatest values of species richness were recorded with moderate thinning process. This indicates that the established pattern of species richness in relation to the process of thinning, as well as with duration of flooding, actually consistent with the intermediate-disturbance hypothesis, suggesting that species richness reaches a maximum at some 'intermediate' level of disturbance. The site score i.e. the determined distribution of oak forests along the ecological gradient on the first canonical axis of ordination biplot has shown greatest significance of three particular factors: type of flooding, average duration of flooding and soil type. Therefore according to determined correlation they are also prominently contributing to the present species variability distributed in the analyzed groups of ecological units regarding the studied gradients.