نتایج جستجو برای: spatial diversity
تعداد نتایج: 539877 فیلتر نتایج به سال:
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...
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...
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...
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...
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, ...
— 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...
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 ...
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 ...
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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