Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 2

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

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
In arid and semi-arid areas, heavy grazing combined with climate change cause land degradation (e.g., desertification). Grazing management is essential for ecosystem recovery and desertification control in these areas, including Northern China’s Horqin Sandy Land. However, the recovery of soil faunal community during grazing exclusion is unknown. We examined plant and soil macro-invertebrate community structure together with soil properties in three treatments in a representative degraded Horqin sandy grassland: exclosure for 15 and 10 years (15EX and 10EX) and long-term continuous grazing (CG). The vegetation cover and height increased significantly and soil bulk density decreased significantly along the gradient from CG to 15EX, but there were no significant differences in soil pH, electrical conductivity, organic carbon and total nitrogen. Soil macro-invertebrate abundance, group richness and diversity increased along the gradient from CG to 15EX, with significant differences in invertebrate abundance and group richness between CG and 15EX; there was no significant differences between CG and 10EX. There were no significant differences in soil macro- invertebrate diversity and evenness between these three treatments. These results suggested that grazing exclusion for at least 15 years might be necessary for the recovery of these fauna. The vegetation height and the soil electrical conductivity, organic carbon, and total nitrogen determined the distribution and community structure of soil macro-invertebrates. Some faunal groups lived in specific habitats due to strong adaptation to different management practices. For example, the Thomisidae, Philodromidae, Salticidae, and Rhopalidae tended to live in habitats with tall vegetation. The Lygaeidae, Miridae, Teneberionidae, and Linyphiidae adapted to live in soil with low soil organic carbon and nitrogen (ungrazed grassland).
Anastatica hierochuntica is a monocarpic desert annual whose dry skeletons, enclosing mature fruits, often persist for a number of years. The aerial seed bank in these hygrochastic ‘resurrection plants’ therefore persists too. Life tables and fecundity schedules were constructed for A. hierochuntica populations raised under four water treatments, equivalent to 100, 200, 500 and 1000 mm rainfall. Seedling survivorship showed a Deevey type III curve for 100 mm, and a type II curve for 200 mm, while 500 and 1000 mm treatments produced Deevey type I curves. Fewer seeds germinated and seedling survivorship was lower in the low water treatments. The stage-specific mortality rate reached 0.75 under the 100 mm treatment in the seed germination stage, compared to 0.08 under the 1000 mm treatment. Increased water availability resulted in greater plant growth and reproductive output, in terms of both number of seeds per individual and reproductive value. In field studies, aerial seed banks of small plant sizeclasses (from 1 to 32 cm³) were depleted within 3-to-7 years. For the large size-classes, > 32 cm³, only a portion (79.7-44.4%) of the seeds produced were dispersed during the observational experiment (the rest remaining within the tumbleweed ball, available for subsequent germination). The projected seed bank life-time for populations raised under different water treatments increased more than fivefold (from 3 to 17 years) for the 100 mm compared to the 1000 mm rainfall treatments. Local persistence of populations was thus likely to be reduced by water stress. Populations of A. hierochuntica characterized by weak plant growth and a preponderance of small size-classes will be more vulnerable to extinction due to their low reproductive output and reduced aerial seed bank reserve.
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.