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Plant-plant interactions, which are defined as the effect of one plant on another of the same or different species, are inherently local in nature. Plants interact in both positive and negative ways, which are governed by the same underlying ecological dynamic processes. The Mexican endemic Picea chihuahuana Martínez is a largely untouched tree species and it is therefore an excellent model for estimating genetic potential of plant-plant interactions under natural conditions. Because of the scarce research examining plant-plant interactions at the genetic level,we tested the hypothesis that specific genetic variants of P. chihuahuana areassociated with (and likely selected by) the presence of particular neighbouring tree species. To explore this question, we applied AFLP genotyping to five P. chihuahuana populations in the State of Durango, North-western Mexico. Under the assumption that the variables genetic variant of P. chihuahuana and nearest-neighbour tree species are directly related to each other, the results show a statistically significant association between such genetic variants – at one AFLP locus in one Picea population – and two nearest-neighbour conifer species (P. chihuahuana Martínez and Pinus arizonica Engelm.). The findings indicate that interactions between genetic variants and species diversity may be crucial in shaping plant communities. However, further studies are required for a better understanding of the possible roles that such associations between genetic variants might play.
Initial populations of club mosses were investigated in pine forests of southern Lithuania (ass. Cladonio-Pinetum and Vaccinio vitis-idaeae-Pinetum). Results show that populations of lycophyta gametophytes in some forest sites can be abundant (up to 500 individuals in a square meter). All juvenile populations were found in localities where recorded tree canopy cover was 30% or less. Localization of subterranean gametophyte populations was determined by juvenile club mosses. We mapped locations of all Lycopodium L. and Diphasiastrum Holub. juvenile sporophytes and gametophytes that occurred within three randomly selected and excavated 0.25 m² sample plots at four pine forest sites in different localities in southern Lithuania. The developmental stage of each individual was recorded. Eight out of twelve soil samples from four research localities contained subterranean gametophytes. In total 277 gametophytes and 124 juvenile sporophytes were recorded. The developmental stage and size of the gametophytes varied. Gametophytes were divided into six categories on the basis of external features. Spatial distribution of gametophytes and juvenile sporophytes were evaluated using a nearest neighbor analysis (NNA). Our results suggest that initial populations of gametophytes in pine forests are multi-aged and display a relatively stable degree of spatial aggregation. Greater aggregation occurred among juvenile sporophytes.
The paper suggests some indicators for the application of spatial methods in field experimentation. The indicators were based on the data from two field-breeding experiments with pea and field bean. Partially balanced square lattice designs were applied. The Smith’s index of soil heterogeneity b, chemical properties of the soil e.g. pH, Mg, P and K contents as well as data obtained from check plots sown with a single variety were used to evaluate spatial variation across the experiments. The Smith’s index of soil variability b showed a potential as a convenient tool to assess the purposefulness of background variation analysis by applying spatial methods. When b<0.6 one can expect a significantly increased efficiency of the experiment. Therefore the application of the nearest neighbour analysis or kriging to the data obtained from a net of check plots can produce the concomitant variable which can reduce the experimental error effectively.
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