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Decomposition rates and changes of carbon and nitrogen contents of Sphagnum litter in mire vegetation can help to explore the ecological effects of climate change and the role of environmental factors from a local to an ecosystem scale. The objective of the study was to determine the relationship between mentioned parameters in small and isolated Sphagnum dominated mires. Measurements had been conducted throughout a year by placing litterbags filled with Sphagnum biomass in three vegetation types (open peat bog, poor fen, alder carr) of a mire ecosystem in Hungary. Peat decomposition rates differed to a great extent; the slowest decomposition rate (39.1±9.52%) was in the alder carr, indicating that slower decomposition could be characteristic for this kind of vegetation type of mire. Between Sphagnum dominated microhabitats, open peat bog showed medium (65.57±4.05) while poor fen the fastest (68.61±5.5) rates in decomposition. The C/N ratio of the Sphagnum litter showed significant decrease (P <0.005) in all studied micro-environments. Slower N release was observed from litter of Alnus dominated association (31.3±6.9%) compared to Sphagnum dominated ones (56.5±8.3%). Our findings showed that the decomposition rates were more dependent on vegetation type than C/N ratio and this relationship was also revealed at a small spatial scale.
The ecophysiological responses of the homoiochlorophyllous desiccation-tolerant (HDT) plant Haberlea rhodopensis showed that this plant could tolerate water deficit and both leaves and roots had high ability to survive severe desiccation. The changes and correlation between CO₂ assimilation, stomatal conductance, contents of photosynthetic pigments, root respiration and specific leaf area during dehydration–rehydration cycle were investigated. The physiological activity of leaves and roots were examined in fully hydrated (control) plants and during 72 h of dehydration, as well as following 96 h of rehydration every 6 and 24 h. After 6 h of dehydration, the stomatal conductance declined and the intercellular CO₂ concentration increased. The reduction in CO₂ assimilation rate was observed after 54 h of dehydration. There was a good correlation between the root respiration and water content. Our results showed that the plasticity of adaptation in leaves and roots were different during extreme water conditions. Roots were more sensitive and reacted faster to water stress than leaves, but their activity rapidly recovered due to immediate and efficient utilization of periodic water supply.
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