Jaroslav Záhora

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human–ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society. Integrated international and long-term collaborative studies covering research gaps will reduce uncertainties and promote further understanding of the nitrogen cycle in various ecosystems.

Different nutrient use strategies of expansive grasses Calamagrostis epigejos and Arrhenatherum elatius

Enhanced nitrogen (N) levels accelerate expansion of Calamagrostis epigejos and Arrhenatherum elatius, highly aggressive expanders displacing original dry acidophilous grassland vegetation in the Podyjí National Park (Czech Republic). We compared the capability of Calamagrostis and Arrhenatherum under control and N enhanced treatments to (i) accumulate N and phosphorus (P) in plant tissues, (ii) remove N and P from above-ground biomass during senescence and (iii) release N and P from plant material during decomposition of fresh formed litter. In control treatment, significantly higher amounts of total biomass and fresh aboveground litter were observed in Calamagrostis than in Arrhenatherum. Contrariwise, nutrient concentrations were significantly higher (11.6–14.3 mg N g−1 and 2.3 mg P g−1) in Arrhenatherum peak aboveground biomass than in Calamagrostis (8.4–10.3 mg N g−1 and 1.6–1.7 mg P g−1). Substantial differences between species were found in resorption of nutrients, mainly P, at the ends of growing seasons. While P concentrations in Arrhenatherum fresh litter were twice and three times higher (1.6–2.5 mg P g−1) than in Calamagrostis (0.7–0.8 mg P g−1), N concentrations were nearly doubled in Arrhenatherum (13.1–15.6 mg N g−1) in comparison with Calamagrostis (7.4–8.7 mg N g−1). Thus, the nutrients (N and mainly P) were retranslocated from the aboveground biomass of Calamagrostis probably more effectively in comparison with Arrhenatherum at the end of the growing season. On the other hand, Arrhenatherum litter was decomposed faster and consequently nutrient release (mainly N and P) was higher in comparison with Calamagrostis which pointed to different growth and nutrient use strategies of studied grass species.

Effect of vermicompost on changes in the bacterial community in maize rhizosphere

The aim of the study was to observe changes in the diversity of bacterial community in maize rhizosphere influenced by organic and mineral fertilization. Four variants of fertilization were tested - vermicompost (VC) at recommended annual dose 40t*ha-1, doubled annual dose of VC, recommended dose of ammonium saltpeter with dolomite (LAD 27) and combination of VC and LAD 27. Experiment was conducted with potted maize plants in controlled conditions of greenhouse during 74 days. Using PCR-DGGE method, we investigated differences in total bacteria community as well as in community of ammonia oxidizing bacteria. Based on occurrence of operative taxonomic units (OTU) we found differences in bacterial species spectra among fertilization variants. The highest Shannon´s biodiversity index was observed in variant with VC addition in dose 80 t*ha-1.The fertilizers effect on diversity of ammonia oxidizing bacteria was not significant however in each variant with vermicompost addition was the occurrence of new specific OTU observed. This OTU was identified as Nitrosospira sp. It was proven that some bacterial species introduced to soil with vermicompost addition can survive for at least 74 days and these bacteria can influence basic functions of soil microbiocenosis in nitrogen cycle.

Biomass Production of Different Grassland Communities under Artificially Modified Amount of Rainfall

ABSTRACT Global climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. A five-year field study with regulated amount of precipitation was executed in different types of temperate grasslands (dry Festuca, wet Cirsium and Nardus grasslands) in three different regions (in lowland, highland and mountain, respectively) in the Czech Republic. Three simulated rainfall treatments were applied: reduced rainfall by 50% (dry), increased rainfall by 50% (wet), and natural rainfall of the current growing season (ambient). The addition of supplemental resources of water exhibited slightly positive relation with the above-ground production (AP), but statistically significant only in the lowland grassland. At all grasslands, both root biomass (RB) and total below-ground biomass (TBB) were significantly higher in wet compared to dry treatments. Significantly increased values of the TBB/AP ratios occurred only in the highland grassland due to enhanced rainfall. The opposite relations were found in lowland grassland where the TBB/AP ratio decreased in response to enhanced rainfall, though not significantly. In the mountain grassland, values of the TBB/AP ratios have shown less variability. The highland wet Cirsium grassland was more sensitive to altered rainfall regimes forming rather lower proportion of below-ground plant production.