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LAI- kvantifikátor pěstebního zásahu =: LAI- quantifier of silvicultural treatment /
Černý, Jakub
The thesis divided into four research topics dealt with an issue of the relation between silvicultural treatments and an amount of the bearing photosynthetically active assimilation apparatus quantified by leaf area index (LAI) in forest stands of an economically important tree species in the Czech Republic. In pure Norway spruce pole stands at the middle altitudinal zone, an effect of silvicultural treatments on the LAI and an efficiency of the photosynthetically active radiation (PAR; 380-720 nm) by foliage within the photosynthetic uptake was evaluated through both canopy production index (CPI) and leaf area effectivity (LAE), and the highest value of the LAI was achieved in a plot with the highest stand density. However, the highest efficiency of the PAR utilisation (CPI, LAE) was noted in the stand, which was tended by thinning from above. Thus, it was proved that not only the total LAI value but especially an efficacy of the leaf area reflecting sun and shade foliage ratio is the more relevant parameter for an evaluation of the effectivity of the thinning treatment. In a forest regeneration, the LAI can also be used for quantification of the regeneration process stage related to a growth dynamic of the natural regeneration. Besides that the newly developed device LaiPen LP 100 (PSI, ČR) for indirect optical LAI estimation was tested within this study. LAI values measured by LaiPen LP 100 showed almost same accuracy of the measurement and identical trends as world standard (LAI-2200 PCA; LI-COR, NE, USA); both at the stand level and the particular measurement point level. Within the study of the efficacy of the PAR utilisation by foliage in photosynthetic uptake expressed by radiation use efficiency (RUE) in pure, fully-stocked and not defoliated Norway spruce mature stands, it was found that mean air temperature most significantly affect annual and monthly values of the RUE with the significant linear relationship (R2 = 0.19; p < 0.05). In the spruce stands, the significant linear relationship (R2 = 0.85; p < 0.001) between an amount of the sequestrated carbon in the form of atmospheric CO2 molecules and the RUE was also proved. The research topic dealt with a seasonal dynamic of the LAI in selected pure and even-aged European beech and sycamore maple stands revealed findings that a culmination of the LAI is achieved within summer months (DOY 120-140) in the investigated stands. The period is the most suitable for estimation and mutual comparison of the LAI due to the stability of its values in investigated (but also in another deciduous) stands. In studied beech and maple stands, maximum LAI values were noted in the second half of June (DOY 170). General findings of underestimation of LAI values estimated by indirect optical methods compared to direct methods were also confirmed. In the last research topic, an effect of the stand age on the leaf area development was studied in pure, even-aged, and fully-leaved (not defoliated) forest stands of an economically important tree species (Norway spruce, Scots pine, silver fir, Douglas fir, European beech, pedunculate oak, and black walnut). Except for black walnut stands, significant linear relationships proving a decrease of the leaf area with increasing age of the stand were found. The relation between the leaf area expressed by effective plant area index (PAIe) and the age of stands was studied for monitoring of the leaf area dynamic within forest stands with a different age.
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