Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 4

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  plant functional group
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Biological soil crusts (BSCs) have a vital role regarding vegetation and soil development in arid and semi-arid areas in the world, and apparently in Iran, where they comprise more than 85% of the land. In this research, the relationship between BSCs and plant functional groups, considering soil parameters along an arid alluvial fan located in Khorasan Razavi province in northeastern Iran, was examined. The sampling carried out in summer, systematically from apex towards base part of alluvial fan, using a 0.25 m² quadrat over a 5-cm thick soil surface. Surface levels were classified into three categories: apex, middle, and base. At each level, 16 samples were taken; in total 48 samples were collected along the alluvial fan from the apex point to the base district. The results showed a strong relationship between BSCs and the soil surface features, and a weak correlation between the plant functional group and soil parameters. BSCs indicated an ecological evolution from apex to the base geomorphic level by soil development; so that BSCs are more developed on the base of alluvial fan, but their diversity is reduced.
We examined to what extend the rate and direction of changes in unmanaged grassland depend on fluctuations in climatic conditions. Vegetation data from permanent plots in a semi-natural grassland in southern Poland collected over 12 years were used. Relations between weather variables, time, and the cover of 41 more frequent species and 14 plant functional groups were analysed. The greatest effect on the dynamics of species and functional groups had precipitation in spring and/or early summer, particularly in the current year. The majority of plant groups were significantly affected also by the temperature in spring and early summer in one of the three previous years. During 12 years, the cover of annuals and biennials, short plants, and plants with small leaves decreased, while the cover of taller plants, plants with larger leaves, and with vegetative spread increased. The analyses suggest that these successional changes were not directly associated with climatic conditions but were affected by them indirectly through interspecific competition. The fluctuations in climatic conditions, chiefly precipitation, had a significant effect on both the composition and the rate of changes in abandoned grassland. The increase in the cover of tall perennial species with broad leaves hindered succession towards woodland despite of the presence of woods in the closed vicinity. It can be expected that during drier periods colonisation of grassland by later successional species could be easier.
The positive relationship between the number of species in an area and the size of the habitat studied (species-area relationship, SAR) is the foundation of ecological theory and the most studied issues in ecology. However, very few studies have addressed SARs and their relationships to functional group richness and the extent of habitat area studied. We analyzed SARs in different functional groups focusing on two types of tropical monsoon rainforests on Hainan Island, China. The number of trees, shrubs, lianas, all species, deciduous species, evergreen species, thorn species, non-thorn species, simple-leaved species, and compound-leaved species were strongly related to the size of the area studied in the two tropical monsoon rainforest communities. And the size of the area studied explained over 94% of the total variations in the number of families and other groups studied. No significant differences were found for the slope of the species-area curve (Z) of different functional groups in two tropical monsoon rainforest communities except for shrubs that were taller in the Terminalia hainanensis community (TC) than in Liquidambar formosana community (LC). In the comparison of different functional groups divided by the same principle in the same tropical monsoon rainforest, no significant difference was found for the value of Z for different functional groups except that Z for lianas were higher than for shrubs in LC. However, the Z of lianas was higher than that of trees and shrubs, and evergreen species and species without thorns had higher Z values than deciduous species and species with thorns. No significant differences were found between simple-leaved species and compound-leaved species in TC. The results indicated the SARs of different plant functional groups can be well-described by the power function, although their slopes differed significantly.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.