Jeňýk Hofmeister

Eutrophication of deciduous forests in the Bohemian Karst (Czech Republic): the role of nitrogen and phosphorus

Abstract In this study, we examined certain plant species for their high need of nitrogen (N>6, Ellenberg’s scale) and identified both conditions of soil nutrients, contents of N and P in leaves and light availability in permanent plots of deciduous forests in the Bohemian Karst (Central Bohemia) between 1997 and 1999. For comparison, a similar habitat was studied in SW-Slovenia. According to our results, factors limiting a development of the ground-layer vegetation of deciduous forests were soil moisture, soil NO3− content and light. The nitrophilic plant cover of the study area required for its development a readily available supply of nitrogen (mainly NO3−). In our opinion, an increase in the quantity of soil-available nitrogen may have been caused by an enhanced deposition of nitrogen. On the other hand, an analysis of leaf N and P indicated that the most of deciduous forests in the Bohemian Karst are still limited less by P than N. Therefore, a successful establishment of nitrophilic species seemed to be dependent on both an adequate supply of N and P in these soils. We observed that soil-extractable P contents were lower in plots covered with less than l% of nitrophilic plants than in all other plots. Diversity of nitrophilic species, i.e., the number of species per plot, was significantly increased in the presence of soil-extractable P. A positive effect of P on both nitrogen mineralisation and nutrition of nitrophilic plants has been reported earlier in the literature. Thus, a successful utilisation of increased N in soils of these ecosystems could occur only in the presence of a sufficiently high P content.

Decline in bryophyte diversity in predominant types of central European managed forests

The extent to which the diversity of forest-inhabiting bryophytes is related to forest management practices has been the subject of a recent study. However, the question of how these practices affect the spatial distribution pattern of bryophyte diversity throughout managed European forests remains unanswered. We surveyed bryophyte diversity in six large forest complexes in the Czech Republic. Our sites encompass a range of managed forest stands (including various temporal phases such as clearings and young forests) across a gradient of environmental conditions. In general, the bryophyte species richness in managed forests was less than in unmanaged forests. Only unmanaged forest stands that provided suitable substrates such as large dead woody debris and large diameter beeches (Fagus sylvatica) were able to support rare bryophyte species. Mature managed forests with simplified tree structure, dominated by either deciduous or coniferous species shared similar bryophyte species richness (α-diversity) and pool (γ-diversity). It appears that forest management, which leads to the loss of old-growth forest attributes, may result in low-diversity bryophyte communities regardless of tree species composition. Nevertheless, bryophyte species turnover (β-diversity) was spatially uniform in mature managed forests dominated by conifers, but quite variable in those dominated by deciduous tree species. Managed forests with diverse tree structure and composition approximated the species pool size of unmanaged forests, in spite of their small contribution to the total area of managed forests. Hence, forest management as commonly applied in the managed forests of the Czech Republic does not appear to be conducive to the persistence of diverse bryophyte assemblages. We suggest that some essential changes in forest management practices are necessary to maintain the conditions favorable to the preservation of bryophyte diversity in central European forests.