The measurement of yearly C-, N- and CH4 balance in characteristic Hungarian wetland ecosystems. Preliminary results

Wetlands macro-vegetation plays an important role in bio-filtration processes. Global warming is anticipated to modify many water ecosystems of the Earth. In submerged plants especially, the photosynthetic rate may be limited by a low availability of dissolved inorganic carbon. Our study demonstrates one of the first results for stand Net Ecosystem CO2 Exchange (NEE) rates for characteristic European aquatic vegetation types based on in situ measurements. To measure NEE of aquatic (floating and submerged) associations at stand level a self-developed, portable, floating open chamber system (d=60cm) was used. Soil fluxes of methane and nitrous oxide were also determined for different wetland ecosystems representing a moisture gradient in Bodrogköz wetlands. As the direction of N2O and methane fluxes (emission or uptake) depends on the soil water content characteristics bi-directional fluxes were observed. Our study demonstrated, based on production analyses and NEE measurements, that from the carbon-dioxide point of view the lakes and streams characterized by significant living plant biomass can be counted as a carbon sequester on a yearly horizon due to the intensive carbon sequestration of submerged and floating vegetations. The majority of examined fluxes and parameters varied considerably among the studied years

Spatial scale-dependence of ecosystem CO2 exchange in three nonarborescent temperate vegetations

Our goal was to investigate the spatial scale-dependence of synphysiological measurements in three different vegetation types: a loess stepp e grassland, a sandy grassland and a ruderal weed community. The former two are widely distributed in the Carpathian Basin and completed with the weed association these are well representing the Hungarian non-arborescent, herbaceous vegetation. To carry out the stand physiological measurements we have constucted gas exchange chambers of several sizes. This size series allowed us to investigate the scale dependence of gas exchange measurements. In all of the three investigated vegetation the variability of C02 -assimilation showed spatial scale-dependence. The highest variability was seen at smaller scales (smaller chamber sizes). The variability of the spatial scale-dependence of the stand photosynthesis was the highest in the sandy grassland, the least organised out of the three investigated community

Effects of different land use change on temperate seminatural grasslands

The specific objectives of this study were to determine the effects of different land use changes (extensive grazing, fertilization and irrigation) on the botanical and soil parameters, plant biomass production and CO2 gas exchanges and to provide data for model development. Experimental work has been carried out for 3 years in two characteristic semi-natural temperate grassland type of Hungary. Small grassland plots were positioned along two transects at fertilized and irrigated sites of loess steppe. At the fertilized (Isaszeg) site, mineral fertiliser was applied once a year at the beginning of the vegetation period, while top spray irrigation was operated continuously during each vegetation period at the irrigated site (Gödöllő). On the plain site an area of 6 ha of dry sand grassland was fenced off from the extensively grazing cattle herd. The shortest response of land-use change can be observed at botanical composition and partly at NEE (CO2), whereas soil parameters are significantly affected at longer time-scale. The observed changes were strongly correlated to climatic conditions, emphasized the importance of the water regime

Health status analysis of Norway spruce and shrubby pine along an elevation gradient

The results of numerous climatic models predict a significant increase in temperature, which coupled with other factors could affect mountain species distribution and community composition. In addition, it can accelerate an upward shift of alpine treelines. However the number of field measurements focusing on the health status of dominant trees in temperate mountains are limited. Our measurements were carried out in the Stuhleck Mountains along an elevation gradient from 850 to 1750 metres. Health status analysis of Picea abies and Pinus mugo have been completed by using FAKOPP 3D acoustic tomography, which is able to detect the size and location of decayed regions in the trunk non-destructively. For modelling the relationship between the decay of tree and other factors simple linear regression models were used. The results showed that the individuals of Picea abies and Pinus mugo had the worst health status in the lowest and uppermost range of the taxa in the studied area. It could be a sign of the upward shift of their range. Positive significant correlation was found between the decay and the ratio of whole trunk/healthy wood both in case of Picea abies and Pinus mugo. It seems, that acoustic tomography measurements are adequate to indicate non-destructively the altitudinal optimum and upward shift of different taxa

How do Central European forest stands respond to climate change - Review

Current global climate change alters the behaviour of species, and this can be also witnessed when investigating the species composition, the structure and the processes of different ecosystems. Today a growing number of researches deal with the climatic exposures of forests, mostly focusing on the responses of the dominant climate susceptible tree species and the direct and indirect impacts of climate change experienced in forests. During literature review we looked for publications investigating the experienced impacts of climate change in our region including responses witnessed in growth, mortality and regeneration capacity of tree species. From different climatic exposures the impacts of increased CO2 level, nitrogen deposition, milder winters and more droughty and drier summers can be experienced most in our region. Publication’s statements on the changes of tree species and forest stands have been grouped and summarized according to the characteristic exposures. Based on the literature data it can be stated that climate change variously alters the tree species composition, mixture ratio and diversity of forest stands and the outcomes of other forest dynamic processes through vitality, production and competitiveness of different tree species

Ecological indicator based comparative study of tree of heaven (Ailanthus altissima) stands’ herb layer

Tree of heaven ( Ailanthus altissima ) is one of the most dangerous and spread woody-stemmed invasive plant species in Hungary. By its nature it transforms its environment and reduces the biodiversity of the area. These processes can be observed studying species composition of habitats heavily infected by tree of heaven. In our research we studied the herb layered species composition of plant communities that were tree of heaven dominated in canopy in Fót, Gyermely, Makád and Tököl. After determining the species associated Borhidi’s relative ecological indicators and Raunkiaer’s life-forms have been applied and analysed for the distribution of the categories. Accordingly most of the species occurring in the herb layer of studied areas were herbaceous. In these stands disturbance tolerant species, generalists and weed species are common, but more, aggressive competitors also appear. These species are indicators of degraded and disturbed habitats however there was also a protected area (Fóti-Somlyó). Summing the indicators of relative temperature figures it can be stated that most of the species indicated the relative temperature demand of submontane broad-leaved forests. According to wetness requirement of the species, studied tree of heaven stands were semihumid. Looking at the relative nitrogen figures, species show a wide variety, but most of them indicate a moderately nutrient-rich, or richer habitat. On herb layer halflight plant species prevailed which indicates that these tree of heaven infected stands were less closed, allowing more light to come down to the herb layer. In continentality suboceanic and intermediate types dominated. The majority of the species is halophob, that does not tolerate the salty environment