نتایج جستجو برای: spatial diversity

تعداد نتایج: 539877  

Journal: :Ecological applications : a publication of the Ecological Society of America 2011
Andreas Flohre Christina Fischer Tsipe Aavik Jan Bengtsson Frank Berendse Riccardo Bommarco Piotr Ceryngier Lars W Clement Christopher Dennis Sönke Eggers Mark Emmerson Flavia Geiger Irene Guerrero Violetta Hawro Pablo Inchausti Jaan Liira Manuel B Morales Juan J Oñate Tomas Pärt Wolfgang W Weisser Camilla Winqvist Carsten Thies Teja Tscharntke

Effects of agricultural intensification (AI) on biodiversity are often assessed on the plot scale, although processes determining diversity also operate on larger spatial scales. Here, we analyzed the diversity of vascular plants, carabid beetles, and birds in agricultural landscapes in cereal crop fields at the field (n = 1350), farm (n = 270), and European-region (n = 9) scale. We partitioned...

Journal: :مدیریت خاک و تولید پایدار 0
شمس الله ایوبی دانشکده کشاورزی، دانشگاه صنعتی اصفهان فریده عباس زاده گروه خاکشناسی- دانشگاه صنعتی اصفهان اعظم جعفری دانشگاه باهنر کرمان حسین خادمی گروه خاکش ناسی دانشگاه صنعتی اصفهان

knowledge about spatial soil variation in terms of measured pedodiversity offers the possibility to estimate the quality and variance within a soil map. diversity indices and abundance distribution models are statistical tools which ecologists have applied for decades for analyzing the intrinsic regularities of various ecological entities. in this study relationships between soils evolution, la...

2003
A. L. F. de Almeida W. C. Freitas J. C. M. Mota F. R. P. Cavalcanti

Spatial multiplexing or BLAST (Bell Labs Layered Space-Time) and space-time block-coding (STBC) are promise approaches that exploits the MIMO channel to provide higher data rates and diversity gains with no sacrifice in bandwidth. In this work we evaluate the performance of a MIMO system that combines transmit diversity and spatial multiplexing schemes. We also propose two effective receiver st...

Journal: :International Conference on Advances in Business, Management and Law (ICABML) 2019

2015
Jani Heino Adriano S Melo Luis Mauricio Bini Florian Altermatt Salman A Al-Shami David G Angeler Núria Bonada Cecilia Brand Marcos Callisto Karl Cottenie Olivier Dangles David Dudgeon Andrea Encalada Emma Göthe Mira Grönroos Neusa Hamada Dean Jacobsen Victor L Landeiro Raphael Ligeiro Renato T Martins María Laura Miserendino Che Salmah Md Rawi Marciel E Rodrigues Fabio de Oliveira Roque Leonard Sandin Denes Schmera Luciano F Sgarbi John P Simaika Tadeu Siqueira Ross M Thompson Colin R Townsend

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted by insect group, latitude, spatial extent, alt...

2003
Sonia Furman Mario Gerla

Spatial diversity has been gaining significant momentum in cellular systems due to its ability to improve radio links in mobile wireless channels. Techniques of spatial diversity have been expanded to build foundations for advanced antenna array technology, to increase capacity in mobile wireless communication systems due to radiation patterns that direct energy only in the intended direction, ...

2003
Gerhard Bauch

— We consider space-time-frequency transmit diversity with orthogonal designs in a broadband OFDM system. Based on capacity considerations for Gaussian as well as real world signal constellations, we show that the concatenation of an outer error control code, a bit interleaver and orthogonal spatial transmit diversity provides an attractive MIMO scheme which is simple and fairly robust to chann...

2011
Matthew N. Rouse Amgad A. Saleh Amadou Seck Kathleen H. Keeler Steven E. Travers Scot H. Hulbert Karen A. Garrett

BACKGROUND Environmental variables such as moisture availability are often important in determining species prevalence and intraspecific diversity. The population genetic structure of dominant plant species in response to a cline of these variables has rarely been addressed. We evaluated the spatial genetic structure and diversity of Andropogon gerardii populations across the U.S. Great Plains ...

2017
Emily L. Dolson Samuel G. Pérez Randal S. Olson Charles Ofria

Spatial heterogeneity is believed to be an evolutionary driver of biodiversity. Variability in the distribution of resource patches can allow an environment to support a wider variety of phenotypes for selection to act upon at the ecosystem level, which may lead to more species. However, the generality of this principle has not been thoroughly tested, as the relevant adaptive dynamics occur on ...

2013
Donald R. Schoolmaster

There is little debate about the potential of environmental heterogeneity to facilitate species diversity. However, attempts to show the relationship between spatial heterogeneity and diversity empirically have given mixed results. One reason for this may be the failure to consider how species respond to the factor in the environment that varies. Most models of the heterogeneity-diversity relat...

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