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:  light availability
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
The capacity of plants to occupy different habitats is made possible by the plastic responses of their presenting in heterogeneous habitats. Light directly influences the plastic responses of plant architectural traits. We measured five years-old saplings of Chinese cork oak growing in different light intensity habitats (forest edge, forest gap and understory). A suite of architectural and leaf morphological attributes indicated a pronounced ability of Chinese cork oak to adapt to shade. Under low light intensity habitats, Chinese cork oak had a significant tendency to invest more in crown growth, characterized by the highest crown area, the lowest crown length ratio and the largest angle of the inclination of the main stem to the vertical. It expressed marked plagiotropic growth in shade indicating a horizontal light-foraging strategy. In addition, Chinese cork oak significantly exhibited the highest specific leaf area and the lowest total leaf area under low light intensity habitats. In shade, they showed some plasticity in displaying most of their leaf area at the top of the crown to minimize self-shading and to enhance light interception. This differentiation can be defined as a plastic phenomenon, likely related to the higher efficiency of light interception and absorption by saplings.
Nutrients may be mobilized from senescing leaves and transported to other plant tissues, enabling plants to conserve them and reuse. Nitrogen and phosphorus are two dominant nutrients related to photosynthetic capacity and limiting plant growth. In this study, we examined the effect of canopy height on nutrient use by analyzing N and P concentrations of green and senescent leaves collected from different canopy heights of Abies georgei var. smithii (Viguie et Gaussen) Cheng growing at the alpine timberline in Sergyemla Mt. (4 350 m a.s.l), southeastern Tibetan Plateau. The results showed that N and P concentrations per unit needle mass decreased significantly with needle age, but no significant difference was found among upper, middle and lower canopy. However, area-based N and P concentrations increased with the height of canopy. The leaf level nutrient resorption and use efficiency varied in the order: upper canopy> middle canopy >lower canopy for both N and P. The higher nutrient resorption efficiency had significant relationship with leaf level nutrient use efficiency, that is, higher leaf level nutrient use efficiency was partly due to the high resorption from senescent needles. Additionally, the higher nutrient resorption was related to high current nutrient concentration. Vertical variations of leaf level nutrient use efficiency in this study reflected the strategy of alpine trees to respond to imbalance between light availability and soil nutrients.
Coppicing is uncommon in Poland; however, some remnants of a previously coppiced oak forest persist in the foothills of the Sudety Mountains (southern Poland). Some of these forests are considered as a kind of thermophilous oak forest, classified as habitat 91I0 in the European programme Natura 2000. As an example of previously coppiced sessile oak (Quercus petraea (Matt.) Liebl.) forest in Poland, the vegetation and environmental factors in the “Wąwoz Lipa” reserve (area 101 ha, altitude ca. 400 m a.s.l.) were surveyed. Canonical correspondence analysis showed a basic compositional gradient of vegetation related to the content of coarse fragments in the soil, light availability and soil pH. The number of species per plot was not correlated with any particular environmental variable; in general, the plant species number and cover decreased in the most exposed sites, where the heat load was highest. We hypothesize that the higher number of species in some plots was the results of an edge effect: this occurred in transitional zones between the most exposed sites, which work as refuges for light-demanding, drought-tolerant species, and less exposed sites, with vegetation typical of acidophilous oak forests. The land relief also allowed the spread of species typical of mesophilous forests, which found refuge in the shaded, wet gorges. Thus, the specific land relief, along with previous coppice management, allowed the coexistence, probably temporally, of species of plants considered typical of different habitats.
Larix chinensis Beissn is an endangered plant found only in the Qinling Mountains, Shaanxi, northwestern China. It is densely distributed in the alpine and subalpine belt on their highest peak Taibai Mountain. Age structure studies along a montane altitudinal gradient would be helpful in understanding the limiting factors on the regeneration of natural forests. The forest was divided into three transects, i.e., lower limit (2900–3000 m), mid-altitude (3100–3200 m) and upper limit (3300–3400 m). The age structures differed across altitude classes. The age structure in the low altitude transect was closed to bell-shaped and characterized by the dominance of adult trees. A reverse-J shape age structure was found in the mid-altitude transect. Multi-modal age distribution was found in the high altitude transect, and was caused by lack of young seedlings and saplings. This suggests that different limiting factors play important roles in shaping the age structure and forest regeneration at different altitudes. In the low altitude, light availability was probably the most important limiting factor. In the mid-altitudinal transect, density dependent intraspecific competition between trees likely controlled regeneration of L. chinensis. We suggest that limiting climatic factors, e.g. temperature, play an important role in determining the age structure of L. chinensis populations in highaltitude areas.
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.