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681.
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KERRY D. WOODS 《Journal of Ecology》2004,92(3):464-476
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The Betula pendula Roth. seeds used in this study were collected from three different natural populations in the province of Lugo (NW Spain). Three samplings were obtained from each population during the dispersal period of the species. The objective of our research was to assess the germination response of the seeds from each population and sampling when exposed to some of the most important effects of fires: high temperatures, ash and their joint effect.Significant differences have been found in the germination percentages of the seeds from the different populations and also from the three samplings. However, the tested effects of fire: heat, ash and their joint effect did not significantly affect the germination percentage of this species. 相似文献
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The population dynamics of Betula pubescens and Picea abies in a boreal forest near Kvikkjokk, northern Sweden, are governed by a process of storm gap regeneration similar to the gap
regeneration described for boreo-nemoral forests. Cumulative age distribution curves, interpreted as static survivorship curves,
lead to a simple theory of differential survival based on properties of the species, i.e. shade tolerance and relative growth
rate. The theory is sustained by diameter and height distributions and by the spatial distributions of logs and of trees in
different life-phases. Species of the field and ground layers respond differentially to gap formation and the ensuing successional
stages. Browsing by moose (Alces alces) may prevent tree species, mainly Sorbus aucuparia, Betula pubescens and Pinus sylvestris, from developing into a tree layer. The regeneration ability for tree species growing in a stand at 460 m a.s.l. is limited
compared with the regeneration at 330 m a.s.l., and typical storm gap formation involving more than one tree seems to occur
rarely if at all, while overthrown trees with exposed rootplates are uncommon. Spruce at 460 m a.s.l. shows also a lower growth
rate and a lower height/diameter ratio compared to the lower situated stands. 相似文献
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Summary Soils influenced by acid mine drainage (pH<5.0) are characterized by low concentrations of essential nutrients and increased solubility of heavy metals. The conditions typically reduce plant establishment and growth. However, river birch (Betula nigra L.) is commonly found along low pH streams in southeastern Ohio. The objective of this study was to determine the concentration of Al, Mn, Ca and Mg inB. nigra tissues.The results indicate Al and Mn are accumulating inB. nigra when compared to other species. Within river birch, Al concentrations are highest in roots; Mn concentrations are highest in leaves. There is not a concomitant reduction in Ca and Mg concentrations as suggested by soil levels. 相似文献
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Photosynthetic and transpiration (E) rates, stomatal conductance, and leaf nitrogen content were surveyed for Myrica gale
var. tomentosa, a N2-fixing wetland shrub, Betula platyphylla var. japonica, and Rhododendron japonicum in Ozegahara moor, an oligotrophic moor
in Central Japan. Net photosynthetic rate saturated with irradiance (Pmax) of M. gale was 15.2-16.5 μmol(CO2) m-2 s-1, higher than those of the other species throughout the growing season. Pmax was positively correlated with leaf N content among the three species. The large leaf N content in M. gale was due to N2-fixation in root nodules. In a comparison of M. gale in two habitats, Pmax, leaf N content, and root nodule development were larger in the wetter habitat. M. gale showed high E and no midday depression
of Pmax even under high irradiance and large vapour pressure deficit between leaves and ambient air on a midsummer day. These traits
of photosynthesis and water relations were associated with the dominance of this shrub in wetter sites such as stream sides
and hollows.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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