In areas where there is a reason for being deciduous (e.g. a cold season or dry season), being evergreen is usually an adaptation to low nutrient levels. Deciduous trees lose nutrients whenever they lose their leaves. In warmer areas, species such as some and grow on poor soils and disturbed ground. In a genus with many broadleaf evergreens, several species grow in mature forests but are usually found on highly acidic soil where the nutrients are less available to plants. In or it is too cold for the organic matter in the soil to decay rapidly, so the nutrients in the soil are less easily available to plants, thus favouring evergreens.
In temperate climates, evergreens can reinforce their own survival; evergreen leaf and needle litter has a higher carbon-nitrogen ratio than deciduous leaf litter, contributing to a higher soil acidity and lower soil nitrogen content. These conditions favour the growth of more evergreens and make it more difficult for deciduous plants to persist. In addition, the shelter provided by existing evergreen plants can make it easier for younger evergreen plants to survive cold and/or drought
Evergreen plants and deciduous plants have almost all the same diseases and pests, but long-term air pollution, ash and toxic substances in the air are more injurious for evergreen plants than deciduous plants (for example spruce Picea abies in European cities).
Deciduous trees shed their leaves usually as an adaptation to a cold or dry season. Most plants are evergreens, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous. Most warm plants are also evergreen. In cool temperate climates, fewer plants are evergreen, with a predominance of, as few evergreen plants can below about -30 °C.
No comments:
Post a Comment