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Jak anatomické a ekofyziologické charakteristiky podrostních bylin temperátních doubrav souvisí s jejich reakcí na sucho
Joura, Libor
Trees modify the environmental conditions for the growth of the shrub and herb layer. Nowadays, the tree layer in forest stands is changing at an unprecedented speed due to the influence of management and the influence of increasing natural mortality. Dense forest stands are considered a refuge for herbs from increased temperature due to global climate change. On the other hand, the surface temperature of leaves in thinned forest stands is indeed higher, but it also gives the possibility of active defense against drought or pathogens. In the diploma thesis, the effect of drought stress and lack of sunlight on anatomical parameters and their correlation with physiology was investigated in selected species of understory herbs growing in temperate oak forests, specifically in the Asarum europaeum L. and Hepatica nobilis Schreb. As a result of drought stress, Asarum europaeum experienced changes in the size of the xylem area of the petiole and the total area of the lumen of the petiole vessels. Furthermore, in the size of the surface area of the vessel lumen, which also changed due to the lack of sunlight. Drought stress had a significant effect on the size of the leaf area in the Asarum europaeum. In the Hepatica nobilis, drought stress had an effect mainly on the diameter of the lumen of the vessels, where stressed plants had a larger diameter of the lumen of the vessels. Drought stress also had a significant effect on the number of vessels in both species. The effect of drought and lack of sunlight had no significant effect on the observed correlations between anatomical and ecophysiological parameters. The Asarum europaeum approaches an isohydric survival strategy. It has a higher degree of stomatal regulation, forms a more efficient but sparser xylem due to a higher diameter of the lumen of the vessels and a larger area of the xylem of the petiole. Hepatica nobilis also forms a large vessel lumen diameter, but the xylem is characterized by lower hydraulic conductivity. It therefore forms a safer and denser xylem, corresponding to an anisohydric strategy. The herbaceous layer carries considerable ecological importance for the structure and function of forest ecosystems. It would be beneficial to perceive the herbaceous and tree layer as a more connected and compact unit. Forest management should consider the importance of the herb layer and also its demands in terms of light and water availability. Trees will thus benefit from the contribution of herbs from the point of view of better nutrient dynamics, the ability to moderate soil erosion or from improving the flow of water through the forest floor.
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