Wyniki wyszukiwania - BazTech

1

Przypadek kontrłaty a stan wiedzy o dachach

Patoka Krzysztof

Materiały Budowlane

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2022

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nr 1

70--71

2

Accuracy of determining height differences based on NRTK VRS measurements and using quasi-geoid model

Kudas Dawid, Wnęk Agnieszka

Geomatics, Landmanagement and Landscape

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2022

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no. 3

59--74

EN

The paper analyses the accuracy of the determination of normal heights in the national spatial reference system using the PL-geoid-2011 quasi-geoid model. The heights were determined using the PL-EVRF2007-NH normal height system. The paper discusses the results of a measurement experiment consisting in measuring 8 points with the use of the Network Real Time Kinematic (NRTK) technique and the Virtual Reference Station (VRS) surface correction generated on the basis of the TPI NETpro commercial network of reference stations and with the use of two global satellite systems (GPS, GLONASS). In the experiment, three measurement schemes were evaluated in relation to the number of measurement epochs recorded above the designated point, as well as the order of recording points. The conducted measurement experiment allowed to determine which of the proposed schemes guarantees the best accuracy from the point of view of establishing a height measurement network with the use of the NRTK technique and VRS corrections. The tests showed that it is possible to determine the height difference between points using the NRTK technique and the VRS method with an accuracy of 0.01m. However, to ensure adequate accuracy, elevation differences must be defined as the differences of the measured heights and should be determined several times and based on independent measurements at the beginning and end of the levelling section. Thus, determining elevation differences with the use of the NRTK VRS technique may be particularly effective in areas with large differences in height, where the determination of elevation differences with the use of classical methods is time-consuming. The obtained elevation differences require tying to the points of the height control network with the use of classical methods.

PL

W artykule przeprowadzono analizę dokładności wyznaczenia wysokości normalnych w państwowym systemie odniesień przestrzennych z użyciem modelu quasi-geoidy PL-geoid-2011. Wysokości wyznaczono w układzie wysokości normalnych PL-EVRF2007-NH. W artykule omówiono wyniki eksperymentu pomiarowego polegającego na pomiarze 8 punktów z użyciem techniki Network Real Time Kinematic (NRTK) i poprawki powierzchniowej Virtual Reference Station (VRS) wygenerowanych w oparciu o komercyjną sieć stacji referencyjnych TPI NETpro i z wykorzystaniem dwóch globalnych systemów satelitarnych (GSP i GLONASS). W eksperymencie walidowano trzy schematy pomiarowe różniące się ilością epok pomiarowych rejestrowanych nad wyznaczanym punktem, jak również kolejnością rejestracji punktów. Przeprowadzony eksperyment pomiarowy pozwolił określić, który z zaproponowanych schematów pozwala osiągnąć najlepsze dokładności z punktu widzenia zakładania wysokościowej osnowy pomiarowej z użyciem techniki NRTK i poprawek VRS. W badaniach wykazano, że możliwe jest określenie przewyższenia pomiędzy punktami z użyciem techniki NRTK i metody VRS z dokładnością 0.01m. Jednakże, aby zapewnić odpowiednią dokładności, przewyższenie musi być określane jako różnica pomierzonych wysokości i powinno być określane kilkukrotnie w oparciu o niezależne pomiary na początku i końcu odcinka niwelacyjnego. W związku z powyższym określenie przewyższeń z użyciem techniki NRTK VRS może mieć szczególnie efektywne zastosowanie w terenach o dużych różnicach wysokości, gdzie określenie przewyższeń z użyciem klasycznych metod jest czasochłonne. Otrzymane przewyższenia wymagają dowiązania do punktów szczegółowej osnowy wysokościowej z użyciem klasycznych metod.

3

Praktyczne doświadczenie z dostępnością – dom bez barier architektonicznych. Analiza zagrożeń obszaru progu

Heinrichsberger Sandra, Junge Knut

Świat Szkła

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2020

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R. 25, nr 2

17--19

4

Największe osiągnięcia budownictwa mostowego w ostatnich latach. Część 2. Inne kryteria oceny

Radomski Wojciech

Builder

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2020

|

R.24, nr 6

46--49

PL

Dokonano przeglądu czołowych w skali świata i kraju osiągnięć mostownictwa, przyjmując za kryteria oceny długość przepraw oraz tras mostowych, wysokość położenia obiektów nad terenem oraz stosowanie niekonwencjonalnych materiałów konstrukcyjnych. Przedstawiono i scharakteryzowano rekordowe osiągnięcia odpowiadające dwóm pierwszym kryteriom. Zwrócono uwagę na rozwój obu tendencji także w Polsce, ale z zachowaniem odpowiednich proporcji wynikających z jej ukształtowania terytorialnego i stopnia zurbanizowania. Zastosowania nowych materiałów konstrukcyjnych ograniczono do przedstawienia krajowych osiągnięć w zakresie wprowadzenia kompozytów polimerowych z włóknami do budowy nowych obiektów mostowych. W podsumowaniu wskazano inne jeszcze kierunki rozwoju mostownictwa, które w opracowaniu świadomie pominięto, a które zasługują na popularyzację.

EN

The top achievements of bridge engineering are presented based on three criteria: lengths of the bridge routs, the high of bridge location over the ground and application of the new structural materials. Presentation of the last one is limited to the use of Fibre Reinforced Polymers (FRP) for construction of the new bridges in Poland. The above criteria are exemplified by bridge structures built recently in the world and in Poland. It is emphasized that the development of the bridge engineering in Poland is in accordance with above mentioned world criteria. The other criteria intentionally omitted in the paper are listed. They can be presented in detail and exemplified in the next papers published in the journal.

5

The influence of height of the weld reinforcement on the cost of additional materials in MAG welding process (135)

Kochanowska Katarzyna, Pakos Ryszard

Welding Technology Review

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2019

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R. 91, nr 11

51--57

EN

This article analyzes influence of the height of the weld reinforcement on the cost of additional materials in the MAG welding process. For this purpose, a simple calculator was created based on which the welds were calculated in the quality levels B, C and D and the costs of additional materials for butt joints made of low-alloy and high-alloy steel and T-joints made of low-alloy steel. Considerations on this subject were carried out based on the PN-EN ISO 5817 standard defining quality levels according to welding nonconformities. The losses resulting from exceeding a given quality level are presented.

PL

W artykule dokonano analizy wpływu wysokości nadlewu spoin czołowych i pachwinowych na koszty materiałów dodatkowych w procesie spawania metodą MAG. W tym celu utworzono kalkulator Excel ułatwiający obliczenie mas spoin w poziomach jakości B, C i D oraz porównanie kosztów materiału dodatkowych złączy doczołowych ze stali niskostopowej i wysokostopowej a także złączy teowych ze stali niskostopowej. Rozważania prowadzono w oparciu o wymagania PN-EN ISO 5817 określające poziomy jakości według niezgodności spawalniczych. Przedstawiono straty wynikające z niedotrzymania wymaganego poziomu jakości.

6

Evaluation of some levelling techniques in surveying application

Pirti Atinc, Hosbas Ramazan Gürsel

Geodesy and Cartography

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2019

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Vol. 68, no. 2

361--373

EN

Applications in geodesy and engineering surveying require the determination of the heights of the vertical control points in the national and local networks using different techniques. These techniques can be classified as geometric, trigonometric, barometric and Global Positioning System (GPS) levelling. The aim of this study is to analyse height differences obtained from these three techniques using precise digital level and digital level, total station (trigonometric levelling) and GPS which collects phase and code observations (GPS levelling). The accuracies of these methods are analysed. The results obtained show that the precise digital levelling is more stable and reliable than the other two methods. The results of the three levelling methods agree with each other within a few millimetres. The different levelling methods are compared. Geometric levelling is usually accepted as being more accurate than the other methods. The discrepancy between geometric levelling and short range trigonometric levelling is at the level of 8 millimetres. The accuracy of the short range trigonometric levelling is due the reciprocal and simultaneous observations of the zenith angles and slope distances over relative short distances of 250 m. The difference between the ellipsoidal height differences obtained from the GPS levelling used without geoid and the orthometric height differences obtained from precise geometric levelling is 4 millimetres. The geoid model which is obtained from a fifth order polynomial fit of the project area is good enough in this study. The discrepancy between the precise geometric and GPS levelling (with geoid corrections) is 4 millimetres over 5 km.

7

Jumping performance and take-off efficiency in two different age categories of female volleyball players

Jandova Sona, Janura Miroslav

Acta of Bioengineering and Biomechanics

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2019

|

Vol. 21, no. 2

55--61

EN

Vertical jump height is recognised as a determinant factor in elite volleyball performance. In previous studies there are different opinions on whether vertical jump height performance improves during maturation or not. The aim of this study was to assess the differences in jumping abilities in two different age groups of female volleyball players and to determine the take-off efficiency during repeated jumps. Methods: Seventeen female volleyball players from two different age categories – adults and under 16 years – participated in this study. Quattro Jump 9290BA force platform (Kistler, Winterthur, Switzerland) was used to assess the jumping performance during squat jumps, counter movement jumps, and 45-second continuous jumps. Results: Jumping performance did not differ significantly between the two groups. The main efficiency of the conversion of mechanical work into mechanical energy was only 24% and it decreased during the test. Conclusions: The influence of age on the jumping performance in a group of female volleyball players was not confirmed. Take-off efficiency was in both groups quite low and it did not improve during the test.

8

Ekrany akustyczne – zasady ustalania położenia i wymiarów względem źródła i odbiorcy hałasu

Motylewicz M., Bohatkiewicz J., Dębiński M.

Materiały Budowlane

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2018

|

nr 12

66--68

PL

Ekrany akustyczne są jednym z najpopularniejszych i dotychczas najpowszechniej stosowanych rozwiązań ochrony przed hałasem na polskich drogach. Wynika to ze stosunkowo prostej, a przede wszystkim znanej technologii ich wykonania oraz wysokiej skuteczności redukcji hałasu. Ich stosowanie budzi często wiele kontrowersji dotyczących zasadności i potrzeby ich użycia, wynikających z dużych kosztów budowy, ograniczeń dostępności do drogi oraz niewielkich walorów estetycznych. Pomimo to dobrze zastosowane i spełniające określone warunki są urządzeniami skutecznymi, a w niektórych przypadkach jedynymi możliwymi zwłaszcza w przypadku niewielkiej ilości miejsca i zabudowie chronionej zlokalizowanej w bliskiej odległości od drogi. Z uwagi na istotny wpływ lokalizacji oraz wymiarów ekranu na skuteczność redukcji hałasu, a także duże koszty ich realizacji, w artykule zwrócono uwagę na poprawny dobór wielkości geometrycznych przy projektowaniu ekranów akustycznych.

EN

Acoustic barriers are one of the most popular and the most commonly used solutions to protect against traffic noise on Polish roads. This is due to the relatively simple and, above all, known technology of their implementation and the high effectiveness of noise reduction when certain conditions are complied. Their use, however, often cause a lot of controversy regarding the validity and need for their use, due to high construction costs, restrictions on access to the road and low aesthetic values. Despite this, well implemented and satisfying certain conditions, acoustic barrier is an effective device, and in some cases the only possible to use – especially when space is tight and protected buildings located in close proximity to the road. Due to the significant impact of the location and dimensions of the acoustic barrier on the noise reduction efficiency, as well as the high costs of their implementation, the article emphasizes the correct selection of geometric sizes in the design of acoustic barriers.

9

Different Patterns of Changes in Foliar Carbon Isotope Composition Along Altitude

He Z., Zhan S., Wang W., Hu L., Wu S.

Polish Journal of Ecology

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2017

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Vol. 65, nr 2

227--235

EN

Three types of alpine plant species, Carex montis-everestii, Quercus aquifolioides and Stipa capillacea, along an altitudinal gradient of 3005-5025 m on the Tibetan Plateau, were chosen to test the generality of the hypothesis that foliar carbon isotope composition (δ13C) of C3 plants increases significantly with altitude and to determine climate drivers shaping its altitudinal pattern. Temperature and relative humidity showed significantly negative correlations with altitude; however, precipitation and soil water potential remained unchanged with altitude. Foliar δ13C of C. montis-everestii, Q. aquifolioides, S. capillacea alone or combined together did not significantly increase with altitude, which does not support the leading hypothesis of increased foliar δ13C with altitude. There was no difference in foliar δ13C among all three species. Multi-factor correlation analyses showed that temperature, precipitation and relative humidity alone did not affect foliar δ13C of C. montis-everestii and S. capillacea, but conferred significant effects on foliar δ13C of Q. aquifolioides.

10

Wpływ metody zagęszczania na rozkład sorpcyjności wzdłuż wysokości elementu betonowego

Kubissa W.

Materiały Budowlane

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2017

|

nr 3

47--49

PL

Sorpcyjność jest jednym z parametrów, które opisują potencjalną trwałość betonu. Jej wartość zależy nie tylko od składu mieszanki betonowej (w tym m.in. w/c), lecz także sposobu jej zagęszczania. W prezentowanych badaniach podjęto próbę określenia wpływu sposobu zagęszczania mieszanki na wartość sorpcyjności betonu i jej rozkładu wzdłuż wysokości elementu. Wykonano badania sorpcyjności betonu o wytrzymałości na ściskanie ok. 60 MPa. Przeprowadzono je na próbkach uzyskanych przez cięcie rdzeni wierconych z bloków betonowych o wysokości 260 mm. Beton zagęszczano trzema różnymi metodami, a sorpcyjność mierzono w różnej odległości od górnej powierzchni bloku. Wyniki badań porównano z wynikami otrzymanymi na próbkach sześciennych o krawędzi 150 x 150 x 150 mm pielęgnowanych w różnych warunkach. Wykazały one wyraźny (w przybliżeniu liniowy) spadek wartości sorpcyjności w zależności od odległości od górnej powierzchni elementu. Wpływ sposobu zagęszczania na wartość sorpcyjności i jej rozkład wzdłuż wysokości elementu betonowego jest również wyraźnie widoczny.

EN

Sorptivity is one of the parameters which describe the durability performance of concrete. Its value depends not only on the composition of concrete mixture (including among others w/c ratio) but also on the curing procedure. The presented study attempts to determine the impact of the compacting procedure on the value of concrete sorptivity and its distribution along the height of the element. Sorptivity tests of concrete with about 60 MPa comressive strength was made. Tests were performed on the specimens obtained by slicing cores drilled from 260 mm high concrete blocks. Concrete in the blocks was compacted by three methods and the sorptivity was measured at different distances from the block upper surface. The results of the tests were compared with the results obtained on the 150 mm cube specimens cured in different conditions. The results showed a clear (approximately linear) decrease of sorptivity values with distance from the upper surface of the element. The influence of the compaction method on the values of sorptivity and it distribution along the height of concrete element is also clearly visible.

11

Altitude Patterns of Leaf Carbon Isotope Composition in a Subtropical Monsoon Forest

Pan S., Zhang W., Zhao M., Li Y., Xu S., Wang G.

Polish Journal of Ecology

|

2016

|

Vol. 64, nr 2

178--188

EN

Leaf carbon isotope composition (δ13C) of both vascular and non-vascular plants were investigated in order to assess their variability along an altitude gradient (414, 620, 850, 1086,1286 and 1462 m) from a subtropical monsoon forest located at Mt. Tianmu Reserve, eastern China. Leaf δ13C values of all plant species ranged from -34.4 to -26.6‰, with an average of -29.8‰. There is no significant difference in leaf δ13C between vascular plants and mosses, however, trees had significantly higher δ13C values than herbs. For pooled data, leaf δ13C was positively correlated with altitude. Leaf δ13C was significantly and negatively correlated with annual mean temperature and atmospheric pressure, while it was significantly and positively correlated with soil water content. Furthermore, there was no relationship between leaf δ13C and soil nitrogen content or soil phosphorus content. The altitudinal trend in leaf δ13C is the consequence of the interaction between temperature, atmospheric pressure and soil water content.

12

Ecological Adaptation of the Seed Microsculptures of Saussurea from Different Altitudes (Qinghai-Tibet Plateau)

Li Z., Du G.

Polish Journal of Ecology

|

2015

|

Vol. 63, nr 4

593--598

EN

The aim of this study was to explore ecological adaptation of seed microsculptures of Saussurea from different altitudes. Scanning electron microscopy was used to observe the cypselae surface of 10 taxa of Saussurea collected from the eastern edge of Qinghai-Tibet plateau, China. The results indicated that the microsculptures had clear and consistent variations in some samples collected from high (4200 m a.s.l.) and low-altitude sites (2200 m a.s.l.). The thickness of stripes and distance between stripes are increasing while sulcus depth is increasing from a low to a high altitude (P < 0.01). The seed-coat surface was becoming rougher from low to high altitude. The surviving rate of seeds was lower at high altitude than that at low altitude in all the species. The surviving rate of the seeds collected from the high altitudes was higher than that of the seeds collected from low altitudes when sown at the same altitude. All the results suggested that there is selection pressure of the altitude on the development of the microsculpture patterns, which increases absorbed sunlight, the residence time of soil water and nutrition. The changes can make the seeds survive better at extreme environments (cold and dry). The cypselae microsculpture patterns should be used as potential adaptation biomarkers for the species of Saussurea from low- to high-altitude.

13

Altitude Patterns of Leaf Carbon Isotope Composition in a Subtropical Monsoon Forest

Pan S., Zhang W., Zhao M., Li Y., Xu S., Wang G.

Polish Journal of Ecology

|

2015

|

Vol. 63, nr 4

512--522

EN

Leaf carbon isotope composition (δ13C) of both vascular and non-vascular plants were investigated in order to assess their variability along an altitude gradient (414, 620, 850, 1086, 1286 and 1462 m) from a subtropical monsoon forest located at Mt. Tianmu Reserve, eastern China. Leaf δ13C values of all plant species ranged from -34.4 to -26.6‰, with an average of -29.8‰. There is no significant difference in leaf δ13C between vascular plants and mosses, however, trees had significantly higher δ13C values than herbs. For pooled data, leaf δ13C was positively correlated with altitude. Leaf δ13C was significantly and negatively correlated with annual mean temperature and atmospheric pressure, while it was significantly and positively correlated with soil water content. Furthermore, there was no relationship between leaf δ13C and soil nitrogen content or soil phosphorus content. The altitudinal trend in leaf δ13C is the consequence of the interaction between temperature, atmospheric pressure and soil water content.

14

Wieżowce rekordowych wysokości. Rola betonu w nowych systemach konstrukcyjnych

Pawłowski Z., Cała J.

Budownictwo, Technologie, Architektura

|

2013

|

nr 4

58--62

15

Methodology for Evaluation of Fabric Geometry on the Basis of the Fabric Cross-Section

Kolcavova Sirkova B., Vysanska M.

Fibres & Textiles in Eastern Europe

|

2012

|

Vol. 20, no. 5 (94)

41--47

EN

A woven fabric structure is defined by mutual threads interlacing in the fabric as well as the basic parameters of the fabric. The interrelation among fabric parameters can be obtained by considering a geometrical model of the fabric and specific experimental methods. The geometrical model is mainly concerned with the shape taken up by the yarn in the warp or weft cross-section of the fabric. This article provides a possible methodology for evaluation of geometric parameters of threads in the real longitudinal and transverse cross-sections of fabric. From an individual cross-section of the fabric using image analysis it is possible to define the diameter of threads, their deformation, thread spacing, the maximum displacement (height of binding wave) of the thread axis, the angle of the thread axis (interlacing angle), the length of the thread axis in the cross-section of the fabric, the crimp of threads in the fabric, and the real shape of the binding wave through wave coordinates. The parameters mentioned are possible to use as input for mathematical modelling of the fabric structure and for prediction of mechanical and end-use properties of fabrics.

PL

Struktura tkaniny określona jest przez wzajemne przeploty nitek i podstawowe parametry tkaniny. Wzajemne zależności pomiędzy parametrami tkaniny mogą być określone poprzez tworzenie odpowiedniego modelu i badania eksperymentalne. Geometryczny model został opracowany poprzez badanie kształtu przeplotu poszczególnych nitek. Opisano odpowiednie metody dla określenia wzdłużnych i poprzecznych przekrojów tkaniny. Na podstawie poszczególnych przekrojów tkaniny można określić średnice nitki, jej deformacje, odległości miedzy nitkami, maksymalne odchylenie od osi nitki, kąt osi nitki, długości osi nitki w stosunku do określonego odcinka tkaniny, skurcz nitki i rzeczywisty kształt przebiegu nitki w stosunku do współrzędnych tkaniny. Powyższe parametry mogą służyć jako wielkości wejściowe modelu dla określenia mechanicznych i użytkowych właściwości tkaniny.

16

Seed mass increase along altitude within four Saussurea (Asteraceae) species in Tibetian Plateau

Wu G., Tian F., Ren G., Liu Z.

Polish Journal of Ecology

|

2011

|

Vol. 59, nr 3

617-622

EN

Seed mass is a critical life-history character in seed evolutionary ecology. Plant species can present responses in seed mass to environment stresses. We tested the hypotheses that seed mass was positively correlated with altitude within species. We selected four congeneric Saussurea species as study objects, and collected their seeds along altitudinal gradients (2100.4200 m a.s.l.) in the alpine area of the Qinghai-Tibetan Plateau, China. Results showed that mean seed mass of the four species were significantly affected by altitude (P <0.001). There was a general trend of an increase in seed weight with altitude among the populations of the four species. In addition, mean seed mass of four species were not significantly different, but all presented a bigger coefficients of variation within species along altitude gradients. Our results indicate selection pressure within species, with larger seeds occurring at higher altitudes.

17

Deskowania systemowe do formowania ścian prostych

Wiatr T.

Materiały Budowlane

|

2011

|

nr 12

15-15

18

The calculation of height and structure parameters of combustion zone in coke-fired cupolas

Longa W.

Archives of Metallurgy and Materials

|

2011

|

Vol. 56, iss. 1

47-61

EN

The calculation formulas of the combustion zone height in the coke-fired cupolas (coke pieces in the form of square based prisms and various dimensions) as well as the structure of combustion zone have been derived in the present work. The structure has been characterized with the following parameters: zone volume, mass of burning coke, number of burning coke pieces and their average dimensions, surface of development of coke pieces, number of their sequences, their volumes and surfaces in sequences, combustion time of coke cartridges, primary height of the filling coke and others. The presented examples illustrate practical calculations and describe the movement of coke from the melting zone to the combustion one as a continuous process at constant height of the combustion zone. Such an approach completely changes the models of combustion and melting processes proceeding at the interface of combustion and melting zones valid so far.

PL

W pracy wyprowadza się wzory do obliczania wysokości strefy spalania w żeliwiakach koksowych (kawałki koksu w kształcie graniastosłupów o podstawie kwadratu i różnych wymiarach), oraz struktury strefy, którą charakteryzują następujące wielkości: objętość strefy, masa palącego się koksu; liczba palących się kawałków koksu i ich średnie wymiary, powierzchnia rozwinięcia kawałków koksu, liczba ciągów kawałków koksu, ich objętości i powierzchnie; objętości i powierzchnie kawałków ciągach; czas spalania nabojów koksu; pierwotna wysokość koksu wypełniającego i in. Zamieszczone przykłady ilustrują praktyczne obliczenia oraz charakteryzują proces przemieszczeń koksu ze strefy topienia do strefy spalania jako proces ciągły, przy zachowaniu stałej wysokości strefy spalania, co całkowicie zmienia dotychczasowe poglądy na temat modelu procesów spalania i topienia, zachodzących na granicy stref spalania i topienia.

19

Altitudinal variability of the soil water content in natural and managed beech (Fagus sylvatica L.) forests

Pichler V., Durkovic J., Capuliak J., Pichlerova M.

Polish Journal of Ecology

|

2009

|

Vol. 57, nr 2

313-319

EN

European beech (Fagus sylvatica L.) ranks as one of the most adaptive species among European indigenous trees. Variable interactions between the trees and soil water depend on both phenotypic plasticity of the species and natural conditions. They are controlled through stomatal regulation and the ability of beech trees to accelerate quickly their growth if available resources increase. However, the effect of forest density at various altitudes on the soil water content in beech stands has been studied rather scarcely. Therefore, we monitored soil moisture by means of Time Domain Reflectometry in series of natural and managed stands located on sites representing the lower altitude (200-550 m a.s.l.), middle altitude (550-1050 m a.s.l.) and higher altitude (1050-1300 m a.s.l.) zones of the natural beech belt in the Western Carpathians, Slovakia. Forest stand density, expressed in terms of basal area, i.e. the sum of cross section areas of the tree stems at 1.30 m height, was unchanged in natural stands, but it was reduced by 60% in the shelterwood stands. In the clear-cuts, all trees were removed. Total soil water content (SWC) under forest stands was calculated in mm as the product of soil moisture and soil depth, the latter acquired by electrical resistivity tomography. SWC differences between natural and shelterwood stands of the lower altitude, middle altitude and higher altitude zones averaged 18 mm, 36 mm and -3 mm, respectively. According to the Friedman test on ranks, followed by post-hoc multiple comparison testing, the difference was only significant within the middle altitude zone. In it, soil water consumption by the natural stand was limited only by the hormonally controlled seasonal regulation. The comparatively low water loss in the shelterwood stand resulted from a small rainfall interception by forest canopy and a decreased soil water uptake due to reduced basal area, leaf area index and simple age-size forest structure. In the lower altitude zone, the precipitation deficit and limited extractability of soil water were responsible for the absence of larger SWC differences. As opposed to that, low potential evapotranspiration prevented any noticeable SWC differences within the higher altitude zone.

20

Population decline of the Little Owl (Athene noctua)in the Czech Republic

Salek M., Schropfer L.

Polish Journal of Ecology

|

2008

|

Vol. 56, nr 3

527-534

EN

A change of land use is often cited as a causal factor in the decline of many species of farmland birds. Populations of the Little Owl (Athene noctua Scop., 1769) have notably decreased throughout Europe in the last 60 years, including the Czech Republic. The aims of this study were to estimate the recent population trend of the Little Owl and to analyze the importance of altitude and grassland habitat within Little Owl territories. The population trend of the Little Owl in the Czech Republic has still decreasing tendency. The population density dropped from 0.33 breeding pairs (bps) 10 km[^-2] to 0.12 bps 10 km[^-2] in the first (1993-1995) and second (1998-1999) monitoring program, respectively. The decline is apparent also from results from last Little Owl monitoring program which were carried out in 2005.2006 on 35 study plots (4607 km[^2]). The average population density was estimated at 0.1 bps 10 km[^-2]. A distinct feature of these recent populations is that they occur in the places with relatively high local density (core areas) in comparison to the surroundings, which are unoccupied. At present, the Little Owl rarely breeds in natural tree cavities, but rather the majority of nesting sites are situated in human artifacts, especially within agricultural objects. Areas in which the Little Owl occurs have a significantly larger proportion of grasslands and are situated at lower altitudes. We suggest that the changes in agricultural landscape associated with disappearance of traditional farming management of grassland habitats, forceful pasturage and regular mowing were the main factors in this long-term population decline. The recent decrease of Little Owls could be also the consequence of the existence of small isolated populations in which mortality is not balanced by immigration from surrounding areas.