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Assembly rules in plant communities
ŠVAMBERKOVÁ, Eva
Understanding the mechanisms of species co-occurrence in plant communities and determining the most important drivers of community assembly is one of the central questions in community ecology. Problematics of assembly rules is relatively difficult and most of the studies are based on null models, simulations, or observational methods rather than on experimental approach. This thesis focused on an experimental approach which can clarify many ecological mechanisms contributing to answer many questions related to assembly rules concept. Research in this thesis was focused both on stochastic and deterministic processes influencing the species community composition. Adding seeds or transplants of different species (including also the non-resident species) into community and also into plots with restricted competition and monitoring their establishment and survival for several years, the research highlighted the important role of priority effects on species community composition, the importance of the biotic filter as one of the main drivers in composition of meadow species and suggested that species composition is necessary to compare with the appropriately defined species pool. Research in this thesis also compared different estimation methods of species pool assessment with experimentally determined species pool trying to find the most appropriate possibility of the estimation of species pool.
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Plant perception of soil heterogeneity in the field
Hrouda, Adam ; Weiser, Martin (advisor) ; Martínková, Jana (referee)
Nutrients are usually patchily distributed in natural soils. Plants are often able to respond to nutrient heterogeneity in artificial conditions by active plastic changes of root system morphology. The occurrence or magnitude of a foraging response can be altered by the presence of competition. However, it is unclear to what extent root foraging takes place in the field. I conducted a field experiment in order to determine the effect of an artificial nutrient patch on fine belowground biomass of (a) an established community and (b) model plants. The study array consisted of a grid of 30×30 cm plots with model plants located in the centre. Half of the plots contained the artificial patch located 5.5 cm from the model plant. Fertilizer patch treatment did not increase mean plot fine underground biomass. Instead, fine underground biomass was higher in places of greater soil moisture estimated from mean plot EIVs. Neither total model plant root biomass nor proportion of roots in the enriched quarter increased in the fertilizer treatment. Competition was probably higher in fertilized than in control plots judging by a 2-fold increase in death rate of model plants. However, greater proportion of model plants flowered in the treatment plots. Possible causes include a plastic response to the patch as well...
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Spatial distribution of plant roots in heterogeneous soils
Hrouda, Adam ; Weiser, Martin (advisor) ; Kuťáková, Eliška (referee)
In natural ecosystems, water and mineral nutrients are unevenly distributed in soil. Plants respond to this heterogeneity with active phenotypic plasticity of their root system. This plasticity can be either morphological, physiological or their combination. Both single-plant and competition experiments reveal that species differ in responses to heterogeneous distribution of nutrients. Based on observed differences, several theories emerged that describe the mechanisms of species coexistence in plant communities. Thanks to many experimental studies we currently have a better understanding of plastic root responses to soil heterogeneity, but the role of root plasticity in community establishment and development remains unclear. Precise observation of field soil heterogeneity is needed together with more realistic experiments reflecting the natural environment.
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