Wyniki wyszukiwania - Biblioteka Nauki

1

Scale effects on sediment yield from badland areas in Mediterranean environments

100%

Martínez-Murillo J. F. , Nadal-Romero E. , Vanmaercke M. , Poesen J.

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tom Vol. 17

105-109

EN

This study investigates area-specific Sediment Yield (SY) in Mediterranean badland areas at different spatial scales using a SY-database compiled from scientific literature. Relationships between the plot and catchment characteristics and the corresponding SY-data are analyzed. Results indicate that in Mediterranean environments SY is larger than in other environments,especially in badlands where a high variability of SY is observed depending on the spatial scale. In intensively gullied badlands,a complex plot or drainage area (A) -SY relationship is observed: for A ranging between 10-5 and 10 ha,SY is very high (mean SY equals 475 t ha-1 yr-1),whereas for A greater than 10 ha,SY decreases with increasing A (mean SY less than 100 t ha-1 yr-1).

2

Land Quality, Development and Space: Does Scale Matter?

100%

Salvati L. , Council of Research in Agriculture – Centre for Plant-Soil Relationships

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EN

This study analyzes empirically the relationship between land quality decline and the spatial distribution of per capita income observed in Italy at different spatial scales and geographical divisions. The aim of this contribution is to verify if a decline in land quality has higher probability to occur in economically disadvantaged areas and if scale may influence this relationship. Per capita income was considered a proxy indicator for the level of socio-economic development and life quality in the investigated area. Changes over time (1990–2000) of a composite index of land quality and per capita income in Italy were regressed at four spatial scales: (i) 20 NUTS-2 regions, (ii) 103 NUTS-3 prefectures, (iii) 784 local districts designed as Local Labour Market Areas (LLMAs), and (iv) 8,101 LAU-1 municipalities. Different specifications were tested, including first, second and third order polynomial equations. Linear models allowed the best fit for data examined at all spatial scales. However, elasticity of the dependent variable to per capita income varied considerably according to scale suggesting that developmental policies may have a limited impact on land quality in vulnerable southern Italian areas compared to northern and central Italy. This study suggests that geographically disaggregated data simulating different spatial levels of governance may offer further insights compared to cross-country datasets indicating targets for multi-scale policies possibly preventing a poverty-desertification spiral.

3

On the scale dependence of evenness

88%

Ulrich W.

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tom Vol. 49, nr 1

91-94

EN

A recently reported (Wilson et al. 1999) effect of spatial scale on evenness is studied and it is shown that such a pattern is not necessarily an effect of changes in community structure at different scales but may simply result as a byproduct from constrains introduced by maximum and minimum allowed densities due to the sampling procedure. Evenness is found to be constant only if the species area relationship of the community under study has exactly the parameter values that are given by the parameter values of the relative abundance distribution of the community. Because such a situation will seldom occur under natural circumstances scale dependence of the evenness (and of related descriptors of structure) is expected to be a general feature.

4

On the scale dependence of evenness

75%

Ulrich W.

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tom 49

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nr 1

5

Shear-generating motions at various length scales and frequencies in the Baltic Sea - an attempt to narrow down the problem of horizontal dispersion

75%

Nerheim S.

Oceanologia

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2004

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tom 46

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nr 4

EN

In the Baltic Proper, the mean circulation is too weak to explain the fast southward spreading of the so-called juvenile freshwater trapped by the seasonal thermocline in the summer season. Improved knowledge of the spatial and temporal scales of the velocity field is needed to better model dispersion. Spatial and temporal scales are investigated using some large historic data sets. Inertial oscillations are almost always present in the Baltic Proper, irrespective of wind conditions and mixed layer thicknesses. Analyses of the coherence in one data set reveal that the inertial oscillations have a horizontal coherence scale of 10–20 km under the conditions experienced during those measurements. Transient eddies and basin-scale modes with weaker periodicity are also indicated in our data sets. A tentative wavenumber spectrum is constructed for the Baltic Proper.

6

Can the studies at a spatial scale of 100s meters detect the spatio-temporal fluctuations of a parasite assemblage?

63%

Parietti M. , Merlo M. J. , Etchegoin J. A.

Acta Parasitologica

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2013

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tom 58

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nr 4

EN

The importance of small-scale heterogeneity in local factors which overrides that of larger-scales factors, suggest that local factors play a major role in determining the richness and prevalence of larval digeneans in intertidal gastropods. The restricted distribution of the snail Heleobia australis along a 500 m transect in Cangrejo creek (Mar Chiquita, Argentina) provides a good opportunity to test the assumption that a study at spatial scale of 100s meters can detect spatiotemporal fluctuations of a larval digenean assemblage. To analyze that, 3600 specimens of H. australis were collected seasonally during the year 2011. A quantitative variation and a space-time interaction between sampling points and seasons of the year for the total prevalence of larval digeneans and snail’s densities were found, as well as a positive correlation with abiotic factors. These results revealed that the fluctuations in the community of larval digeneans of the snail H. australis can be detected at small spatial scale, using its natural distribution of 500 m. This study also highlights the importance of seasonality as a factor that must be considered in studies focused on the search for patterns structuring the communities of larval digeneans, at medium and large scales.

7

From dispersal to landscapes: progress in the understanding of population dynamics

63%

Lidicker W. Z. J.

Acta Theriologica. Supplement

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2002

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tom 47

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nr 1

EN

The development of our understanding of population dynamics over the past 50 years is reviewed from a personal perspective. An early emphasis on population vital rates was superceded by recognition of the importance of the specific community context of focal populations, and most recently has in turn been enriched by a landscape perspective. Certain basic principles are outlined including the value of a systems context for population analyses, the power of a dual mechanistic and contextual perspective, and the inevitability of density control in a finite biosphere. Numbers are determined by the balance of two complex parameters: p - the per capita growth promoting (enhancing) forces, and s - the per capita growth suppressing forces. Multiple factor explanations of demographic behavior are therefore to be expected, as well as temporal and spatial variations in them. An appreciation for the potential role of dispersal as a population vital rate led to the development of metapopulation theory. A renewed understanding of the role of community context in population dynamics provoked the realization that a multi-factor approach was required. This in turn allowed us to reconcile the reality of local demographic complexity with global generalizations. Finally, the introduction of landscape ecology into demographic thinking added many new insights. It is now appreciated that a spatially explicit mosaic of habitat patches, edge effects, corridors, and even the proportion of favorable to marginal habitats can all be critically important factors in influencing population dynamics.

8

Badanie czasowej i przestrzennej makroskali turbulencji w korycie o złożonym przekroju poprzecznym

51%

Koziol A. P.

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2008

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tom 07

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nr 4

PL

Przedstawiono czasową i przestrzenną makroskalę turbulencji obliczoną na podstawie pomierzonych chwilowych wartości podłużnej składowej prędkości w pionach dwudzielnego trapezowego przekroju koryta. Chwilowe wartości prędkości mierzono w korycie głównym i na terenie zalewowym dla trzech napełnień. Badania wykazały, że czas osiągnięcia wartości zero przez funkcję autokorelacyjną wynosił od 0,78 do 11,98 s, a wartości makroskali czasowej zmieniają się w przedziale od 0,07 do 1,15 s. W trzech wariantach, niezależnie od głębokości, występują jednakowe tendencje wartości względnej długości makrowirów na głębokości. Względne długości makrowirów (0,1–2,5) są większe na terenach zalewowych niż w korycie głównym, na terenie zalewowym największe występują w pobliżu koryta głównego, a najmniejsze nad dnem koryta głównego.

EN

Investigations of the time and spatial macro-scale of the present paper are based on the measurements of instantaneous velocities in a two-stage trapezoidal channel under three various depth in the channel. These investigations have shown the following: the values of time macro-scale have changed in range since 0.07 to 1.15 s; in all three tests the distributions of the sizes of the eddies reveal stable regularity; the relative length of eddies are bigger on the flood plains and achieve value of 0.1 to 2.5 of the flow depths on the flood plains, whereas in the main channel the sizes of largest eddies do not exceed the value of 1 of the total water depth.

9

Czasowa i przestrzenna makroskala turbulencji strumienia w dwudzielnym trapezowym korycie z drzewami na terenach zalewowych

44%

Koziol A.

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nr 2

PL

W artykule przedstawiono makroskale czasową i przestrzenną turbulencji strumienia wody obliczone na podstawie chwilowych wartości podłużnej składowej prędkości w pionach dwudzielnego trapezowego przekroju koryta. Chwilowe wartości prędkości mierzono w korycie głównym i na terenie zalewowym dla różnych napełnień. Wyniki obliczeń makroskal turbulencji przedstawiono dla koryta głównego i terenów zalewowych z drzewami i bez. Badania wykazały, że wartości makroskali czasowej zmieniają się w przedziale od 0,1 do 1,2 s. We wszystkich wariantach, niezależnie od głębokości występują jednakowe tendencje wartości względnej długości makrowirów na głębokości. Względne długości makrowirów (0,1–2,5) są większe na terenach zalewowych niż w korycie głównym, gdzie wartości nie przekraczają 1,2 głębokości. Największe długości makrowirów stwierdzono na terenie zalewowym w pobliżu koryta głównego w obrębie interaktywności strug cieczy. Najmniejsze makrowiry występują nad dnem koryta głównego.

EN

Investigations of the time and spatial macro-scale of the present paper are based on the measurements of instantaneous velocities in a two-stage trapezoidal channel under five various tests in the channel. The results of calculations of macro-scale of turbulence were showed for the main channel and floodplains with trees and without. These investigations have shown the following: the values of time macro-scale have changed in range since 0.1 to 1.2 s; in all five tests the distributions of the sizes of the eddies reveal stable regularity; the relative length of eddies are bigger on the floodplains and achieve value of 0.1 to 2.5 of the flow depths on the flood plains, whereas in the main channel the sizes of largest eddies do not exceed the value of 1.2 of the total water depth. The largest lengths of eddies were affirmed on the floodplains in vicinity of the main channel in zone of interaction. The smallest eddies are over the bottom of the main channel.