13 research outputs found
Genetic variation for sensitivity to a thyme monoterpene in associated plant species
Recent studies have shown that plant allelochemicals can have profound effects on the performance of associated species, such that plants with a history of co-existence with âchemical neighbourâ plants perform better in their presence compared to naĂŻve plants. This has cast new light on the complexity of plantâplant interactions and plant communities and has led to debates on whether plant communities are more co-evolved than traditionally thought. In order to determine whether plants may indeed evolve in response to other plantsâ allelochemicals it is crucial to determine the presence of genetic variation for performance under the influence of specific allelochemicals and show that natural selection indeed operates on this variation. We studied the effect of the monoterpene carvacrolâa dominant compound in the essential oil of Thymus pulegioidesâon three associated plant species originating from sites where thyme is either present or absent. We found the presence of genetic variation in both naĂŻve and experienced populations for performance under the influence of the allelochemical but the response varied among naĂŻve and experienced plant. Plants from experienced populations performed better than naĂŻve plants on carvacrol soil and contained significantly more seed families with an adaptive response to carvacrol than naĂŻve populations. This suggests that the presence of T. pulegioides can act as a selective agent on associated species, by favouring genotypes which perform best in the presence of its allelochemicals. The response to the thyme allelochemical varied from negative to neutral to positive among the species. The different responses within a species suggest that plantâplant interactions can evolve; this has implications for community dynamics and stability
Effects of nitrogen deposition on soil and vegetation in primary succession stages in inland drift sands
Ecosystem responses to reduced and oxidised nitrogen inputs in European terrestrial habitats
Differential effects of oxidised and reduced nitrogen on vegetation and soil chemistry of species-rich acidic grasslands
Emissions and deposition of ammonia and nitrogen oxides have strongly increased since the 1950s. This has led to significant changes in the nitrogen (N) cycle, vegetation composition and plant diversity in many ecosystems of high conservation value in Europe. As a consequence of different regional pollution levels and of the increased importance of reduced N in the near future, determining the effect of different forms of N is an important task for understanding the consequences of atmospheric N inputs. We have initiated three replicated N addition experiments in species-rich, acidic grasslands spanning a climatic gradient in the Atlantic biogeographic region of Europe in Norway, Wales and France at sites with low levels of pollution. N was added in two doses (0 and 70 kg N haâ1 yearâ1 above background) and in three forms (oxidised N, reduced N and a 50â50 combination). After 2.5 years of N additions, the effects of these treatments on plant biomass, plant nutritional status, soil pH and soil nutrient availability were determined. Impacts of the N additions were observed within the 2.5-year research period. In some cases, the first signs of differential effects of N form could also be demonstrated. In the French site, for example, grass biomass was significantly increased by the oxidised N treatments but decreased by the reduced N treatments. In the Norwegian site, the reduced N treatments significantly reduced soil pH, whereas oxidised N did not. Effects on nutrient availability were also observed. These experiments will be continued to elucidate the longer term impacts of N deposition on these grasslands
Productivity depends more on the rate than the frequency of N addition in a temperate grassland
Linkages between aboveground and belowground community compositions in grasslands along a historical land-use intensity gradient
Effects of summer flooding on floodplain biogeochemistry in Poland; implications for increased flooding frequency
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