Root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate     

Xiang Xu  Huade Guan  Grzegorz Skrzypek  Craig T. Simmons 《水文研究》2019,33(18):2394-2407

The root‐zone moisture replenishment mechanisms are key unknowns required to understand soil hydrological processes and water sources used by plants. Temporal patterns of root‐zone moisture replenishment reflect wetting events that contribute to plant growth and survival and to catchment water yield. In this study, stable oxygen and hydrogen isotopes of twigs and throughfall were continuously monitored to characterize the seasonal variations of the root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate in South Australia. The two studied hillslopes (the north‐facing slope [NFS] and the south‐facing slope [SFS]) had different environmental conditions with opposite aspects. The twig and throughfall samples were collected every ~20 days over 1 year on both hillslopes. The root‐zone moisture replenishment, defined as percentage of newly replenished root‐zone moisture as a complement to antecedent moisture for plant use, calculated by an isotope balance model, was about zero (±25% for the NFS and ± 15% for the SFS) at the end of the wet season (October), increased to almost 100% (±26% for the NFS and ± 29% for the SFS) after the dry season (April and May), then decreased close to zero (±24% for the NFS and ± 28% for the SFS) in the middle of the following wet season (August). This seasonal pattern of root‐zone moisture replenishment suggests that the very first rainfall events of the wet season were significant for soil moisture replenishment and supported the plants over wet and subsequent dry seasons, and that NFS completed replenishment over a longer time than SFS in the wet season and depleted the root zone moisture quicker in the dry season. The stable oxygen isotope composition of the intraevent samples and twigs further confirms that rain water in the late wet season contributed little to root‐zone moisture. This study highlights the significant role of the very first rain events in the early wet season for ecosystem and provides insights to understanding ecohydrological separation, catchment water yield, and vegetation response to climate changes.  相似文献   

Modeling and presenting incomplete and uncertain data on historical settlement units     

Grzegorz Myrda  Bogumi&#x; Szady  Agnieszka &#x;awrynowicz 《Transactions in GIS》2020,24(2):355-370

When entering information about changes of settlements in time into a database, we are dealing with direct facts from historical sources and with interpretations. The source information generally relates to an event or situation at a specific time. This means that we only fill in the parts of the timeline with data objects called (partial) manifestations; however, lack of data does not mean that settlement did not exist. It would take a lot of time to interpret and enter missing information manually. In this article we present a database schema, database procedures and algorithms to generate aggregated settlement unit manifestations in an automated way from their partial manifestations. As a result, it is possible to obtain a continuous history of a given settlement so as to present it on a map.  相似文献   

The discovery of the Siberian Traps Large Igneous Province in 1870s,and the leading role of Aleksander Czekanowski     

Grzegorz Racki 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(3):369-391

Flood basalts (traps) and large igneous provinces (LIPs) are essential topics in modern geology. However, little is known about the stages of recognition of particular LIPs, including a giant continental LIP in Siberia. Even though basalt occurrences were reported from the region from the end of the 18th century (e.g., by Kozitsky, Middendorf, Schmidt and Lopatin), the first ample data were provided by the Polish geologist Aleksander Czekanowski (1833–1876). He was educated at the Universities of Kiev and Dorpat but exiled to Siberia for participating in the Polish January Uprising in 1863. Czekanowski organised three expeditions to poorly known parts of Central Siberia, which were initiated by exploring the Lower Tunguska River Basin. In the summer of 1873, he discovered many exposures of basalts and related tuffs. After an expedition to the Olenek River region in 1874, he was aware of a vast extent of basalt sequences and the critical impact of the “powerful volcanic floods” that immensely transformed the uplifted continent. Czekanowski emphasised “the discovery of previously unknown areas of igneous rocks of so large an extent that it exceeds the size of any other of its kind.” Studies of the volcanic series developed towards the end of the century, as summarised in an influential treatise from 1901 by the great Austrian geologist Eduard Suess. Czekanowski, distinguished in Seuss's monograph, is occasionally appreciated as the discoverer of the Siberian Traps but should also be adequately honoured in the neocatastrophism-based geology of the 21^st century.  相似文献   

Changeability of Movable Bed‐Surface Particles in Natural,Gravel‐Bed Channels and Its Relation to Bedload Grain Size Distribution (Scott River,Svalbard)          下载免费PDF全文

Waldemar Kociuba  Grzegorz Janicki 《Geografiska Annaler: Series A, Physical Geography》2015,97(3):507-521

The presented paper analyses the variability of grain size distribution parameters of bedload transported by the gravel‐bed Scott River (Svalbard) draining a glacier catchment with an area of 10 km². The grain size distribution analysis is one of the basic elements of identification of the fluvial transport mechanisms in gravel‐bed rivers. It is used for the determination of threshold values for bedload movement. It is also treated as an important indicator of the origin, routes of distribution, and conditions of transport and deposition of fluvial bedload. The field study in a natural proglacial gravel‐bed channel was carried out at two reaches in the mouth section of Scott River. The study revealed relatively high temporal variability and similar mean parameters of grain size distribution in conditions of low discharges. Bedload transport rates reached a mean of 71.9–76.0 kg d^?1 in channel cross‐section. Bedload texture was dominated by gravels with a proportional contribution of the fine‐grained fraction along with very fine‐grained gravels (8‐2 mm) of 38.8%. The medium‐grained fraction (16‐8 mm) constituted 33.7%, with a lower contribution from the coarse‐grained fraction (32‐16 mm) of 23.2%, and the very coarse‐grained fraction (64‐32 mm) of 4.4%. Two periods in the course of bedload transport and distribution of grain size distribution parameters were distinguished based on variation of hydro‐meteorological conditions. The first half of the measurement period was distinguished by significantly higher values of daily loads and increased contribution of the coarse‐grained and very coarse‐grained fraction (28–31% and 6.2–6.6%, respectively). During this time, the river discharged up to 94% of bedload. This resulted in a clear tendency for riverbed scouring. The second half was distinguished by generally low daily bedload transport rates (<10 kg d^?1), an increase in contribution of fine‐ and very fine‐grained gravels (42–55.6%), and a change in the tendency to aggradation. Grain size indices were more varied, and grains were usually finer and better sorted. Selective transport processes, often related to redeposition, were dominant in the channel. Along with an increase in flow velocity, conditions for material deposition became more variable. This was manifested in weaker sorting and an increase in grain diameter.  相似文献   

Density and magnetic models of the lithosphere along CELEBRATION 2000 profile CEL01     

Teresa Grabowska  Grzegorz Bojdys  Miroslav Bielik  Kristián Csicsay 《Acta Geophysica》2011,59(3):526-560

The paper presents 2D density and magnetic models of the crust and upper mantle along the DSS line profile of the CELEBRATION 2000 project that crosses the most important geological units in Central Europe. These are the Alps-Carpathians-Pannonian (ALCAPA) region, the SE part of the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ) and a fragment of the SW portion of the East European Craton (EEC). The density and magnetic models were constructed on the basis of a 2D model of P-wave velocity converted into density model, geological data as well as geothermal data and the results of integrated geophysical modelling for the lithosphere-asthenosphere boundary.  相似文献   

Comparison of volumetric and remote sensing methods (TLS) for assessing the development of a permanent forested loess gully     

Kociuba  Waldemar  Janicki  Grzegorz  Rodzik  Jan  St&#;pniewski  Krzysztof 《Natural Hazards》2015,76(1):139-159

The gully systems develop a compact network dissecting the loess cover of the NW part of the Lublin Upland. They are overgrown by dense and multi-storey forest assemblages. It is very difficult to apply teledetection techniques, GPS positioning, and geodesic tools, such as a laser rangefinder or total station, for monitoring of gully development. The detailed research, involving the comparison of traditional and modern methods, was conducted in a gully with a secondary erosional dissection, developing in the gully bottom with varied intensity for the last 15 years. In the period of comparative research (2012/2013), the rate of development of the erosional dissection was measured by means of traditional methods as well as a Leica HDS 7000 laser scanner. 3D laser scanning permitted precise terrain modelling and the assessment of qualitative and quantitative spatial changes. This paper compares the results of three measurement campaigns. The analysis showed intensive development of the dissection, manifested in an increase in its volume (37 %), retreat of the erosion scarp (32 m), deep erosion (19 %), and lateral erosion (27 %). Registered moderate snowmelt in 2013 caused the volume dissection to increase by 57 m³, mainly as a result of the gully bottom scouring. During heavy rainfalls in June, the landforms were widened by a further 217 m³ and observed deepening and widening of erosive potholes. The prevalence of deep erosion resulted in the transformation back into a V-shaped cross section. A total of 37.3 Mg km⁻² of material was discharged from the gully catchment during snowmelt runoffs in 2013. A precipitation event in June 2013 caused the discharge of 856.9 Mg km⁻² of material from the catchment. The obtained results confirm that snowmelt erosion determines the spatial development of perennial gullies, but the volume of material discharged from the catchment depends on the occurrence of extreme precipitation during the warm season.

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A reconstruction of the palaeohydrological conditions of a flood‐plain: a multi‐proxy study from the Grabia River valley mire,central Poland          下载免费PDF全文

Dominik Pawłowski  Grzegorz Kowalewski  Krystyna Milecka  Mateusz Płóciennik  Michał Woszczyk  Tomasz Zieliński  Daniel Okupny  Wojciech Włodarski  Jacek Forysiak 《Boreas: An International Journal of Quaternary Research》2015,44(3):543-562

This study investigated the Grabia River valley mire in central Poland to reconstruct its palaeoenvironmental conditions from the Younger Dryas to the present. We analysed sedimentological, biological and geochemical data from the palaeo‐oxbow lake and valley mire to identify the principal hydrological trends, especially episodes of high water level. During the Lateglacial and Holocene, the Grabia River had a meandering channel, and its hydraulic parameters and the channel dimensions changed in response to climatic oscillations and vegetation development. We identified phases of high flood intensity and high groundwater level that correlate with regional and supraregional climatic events. The frequency and timing of palaeohydroclimatic oscillations show strong similarities to records from other sites in Poland and the rest of Europe. We show that various analytical methods, namely, pollen, plant macrofossils, Cladocera, Chironomidae, sedimentological, geochemical and radiocarbon data, can be effective tools for reconstructing past hydroclimatic changes in palaeo‐oxbow lakes and investigating the effects of past climate changes on river environments. The high sensitivity of the biota, especially Cladocera, to changes in water level permits the reconstruction of palaeoecological changes, especially flood episodes that occurred in the river valley. In particular, the increase in the proportion of sediment‐associated Cladocera and pelagic taxa was closely correlated with floods. Through comparisons with the palaeobiological data, geochemical data allowed the identification of humid phases within the fen associated with a rising groundwater table, direct fluvial activity (floods) and alluvial deposition. We also discuss the limitations of palaeohydrological reconstructions based on these proxies, especially on fossil aquatic invertebrates.  相似文献   

CME Velocity and Acceleration Error Estimates Using the Bootstrap Method     

Grzegorz Michalek  Nat Gopalswamy  Seiji Yashiro 《Solar physics》2017,292(8):114

The bootstrap method is used to determine errors of basic attributes of coronal mass ejections (CMEs) visually identified in images obtained by the Solar and Heliospheric Observatory (SOHO) mission’s Large Angle and Spectrometric Coronagraph (LASCO) instruments. The basic parameters of CMEs are stored, among others, in a database known as the SOHO/LASCO CME catalog and are widely employed for many research studies. The basic attributes of CMEs (e.g. velocity and acceleration) are obtained from manually generated height-time plots. The subjective nature of manual measurements introduces random errors that are difficult to quantify. In many studies the impact of such measurement errors is overlooked. In this study we present a new possibility to estimate measurements errors in the basic attributes of CMEs. This approach is a computer-intensive method because it requires repeating the original data analysis procedure several times using replicate datasets. This is also commonly called the bootstrap method in the literature. We show that the bootstrap approach can be used to estimate the errors of the basic attributes of CMEs having moderately large numbers of height-time measurements. The velocity errors are in the vast majority small and depend mostly on the number of height-time points measured for a particular event. In the case of acceleration, the errors are significant, and for more than half of all CMEs, they are larger than the acceleration itself.  相似文献   

Plant assemblage from Opole,southern Poland: New data on Late Cretaceous vegetation of the northern part of the European Province     

Bartosz J. Płachno  Agata Jurkowska  Grzegorz Pacyna  Elżbieta Worobiec  Przemysław Gedl  Ewa Świerczewska-Gładysz 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):159-170

This paper presents the results of studies on plant macroremains found in the upper Turonian of the Folwark Quarry, Opole, Poland, associated with palynological studies of the host rocks. In addition to a few macrofossils (gymnosperm wood, conifer Geinitzia reichenbachii and fern ?Didymosorus) rich sporomorphs (bryophyte, lycopod and fern spores, conifer and angiosperm pollen grains) and marine palynomorphs (mainly dinoflagellate cysts) were recorded. The palynological analysis revealed that the vegetation on the neighbouring land (the East Sudetic Island) in the late Turonian was much more diverse than could be reconstructed based on only macrofossil remains. The latter are taxonomically restricted and dominated by one gymnosperm species (Geinitzia reichenbachii), which make them similar to most neighbouring, coeval Central European assemblages. Its over representation is, thus, a result of taphonomy.  相似文献   

GRS 1915+105: the brightest Galactic black hole     

Chris Done  Grzegorz Wardzi&#;ski  Marek Gierli&#;ski 《Monthly notices of the Royal Astronomical Society》2004,349(2):393-403

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