Reduced soil tillage practices are claimed to improve soil health, fertility and productivity through improved soil structure and higher soil organic matter contents. This study compares soil structure stability of soil aggregates under three different tillage practices: conventional, reduced and no tillage. The erosive strength of soil aggregates has been determined using the abrasion technique with the soil aggregate erosion chambers (SAE). During abrasion soil aggregates have been separated into the exterior, transitional and interior regions. The forces needed to remove the material from the aggregate were calculated as erosive strength and compared with the tensile strength of the aggregates derived from crushing tests. The relationship between aggregate strength and other soil properties such as organic carbon and hydrophobic groups’ content has also been identified. The results show that erosive and tensile strength of soil aggregates is very low in topsoil under conventional and reduced tillage comparing with the subsoil horizons. Negative correlation was found between the content of organic carbon, hydrophobic compounds and erosive aggregate strength which suggests that the stabilising effect of soils organic carbon may be lost with drying. The positive relationship between the tensile strength and erosive strength for aggregates of 8–5 mm size suggests that the total strength of these aggregates is controlled by the sum of strength of all concentric layers.
This study introduces the possibility theory, the foundations of which were laid by Zadeh (1978), using the fuzzy sets theory, and it clarifies its basic concepts and principles. The study was aimed to verify methodological procedures of the possibility theory in current water management tasks. The case study examined possibilities of simultaneous occurrence of several causal factors of hydrological situations, and their impacts on water sources in changed climatic conditions. The second task was focused on the assessment of effects of climatic change on the storage function of the Šance reservoir in the Odra River catchment. In the end, problems open up for further research are outlined. and Studie uvádí do problematiky teorie možnosti, jejíž základy položil Zadeh (1978) s využitím teorie fuzzy množin, a objasňuje její základní pojmy a principy. Cílem studie bylo ověřit metodické postupy teorie možnosti na aktuálních vodohospodářských úlohách. V případové studii se zkoumaly možnosti současného nastání několika příčinných faktorů hydrologických situací a jejich dopady na vodní zdroje ve změněných klimatických podmínkách. Ve druhé úloze byly posuzovány dopady klimatické změny na zásobní funkci nádrže Šance v povodí Odry. V závěru se uvádějí problémy otevřené pro další výzkum.
Following the Article 16 (7) of the Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for Community action in the field of water policy Commission shall submit proposals for environmental objectives applicable to the concentrations of the priority substances in surface water, sediments or biota. In the absence of agreement at Community level up to the deadline given by the directive Member States shall establish environmental objectives themselves. Within the framework of legislative preparation to this situation we have evaluated the relationships between particular parameters of surface water and total suspended solids contamination with heavy metals and with arsenic as one group of priority substances. Neither valid Decree No 82/1999 Coll. nor the amendment include such environmental objectives at present. and Podle čl. 16 (7) Směrnice 2000/60/ES Evropského parlamentu a Rady ustavující rámec pro činnost Společenství v oblasti vodní politiky má Komise předložit Evropskému parlamentu a Radě návrhy environmentálních standardů pro koncentrace prioritních látek v povrchových vodách, sedimentech a v biotě. V případě absence úmluvy na úrovni Společenství do termínu daného směrnicí musejí členské státy stanovit tyto environmentální standardy samy. V rámci legislativní přípravy na takovou eventualitu jsme proto hodnotili vztahy mezi jednotlivými parametry kontaminace vody a plavenin těžkými kovy a arsenem jako jednou skupinou prioritních látek. Platné Nař. vl. ČR č. 82/1999 Sb. ani připravovaná novela zatím environmentální standardy pro sedimenty (a tedy ani plaveniny) a biotu nezahrnují.
Interception is one of the most underestimated processes in hydrological cycle in arid and semiarid regions. In Qilian Mountains of northwestern arid and semiarid China, the Qinghai spruce (Picea crassifolia) forest plays an important role in the hydrological cycle of the inland Heihe River basin. The historical disturbance of Qinghai spruce forest has resulted in various ecological problems. In order to realize the sustainable development of Heihe River basin, the Chinese government implemented restoration practices for Qinghai spruce in the past three decades. In this study, we estimated the rainfall interception in the actual and potential distribution of Qinghai spruce forest. Some of the important findings include: (1) The interception ratio of rainfall events ranged from 11-51% with a mean value of 27.02%; (2) Totally, 147 Mt of rainfall is intercepted by canopy of actual Qinghai spruce forest, in the projected potential distribution of the forest, totally 407 Mt of rainfall will be intercepted.