November 28, 2021
A deciduous forest (deciduous forest in English) is a forest that drops leaves all at once in a certain season.
A warm and water-sufficient environment is ideal for trees, and if this condition is maintained throughout the year, an evergreen forest will be established there. On the other hand, if there is a time when this condition cannot be maintained, the tree will have to deal with it. At this time, the biggest problem is what to do with the leaves. Leaves are an important part of trees that produce nutrition through photosynthesis, and we want them to last a long time. However, the leaves are thin and protruding, and the structure is vulnerable to dryness and cold air.
If the dry and winter seasons are not so bad, the trees will survive without throwing away their leaves. Instead, the leaves are small and thick, and the cuticle layer is developed to make them durable in the dry and cold seasons.
However, to the extent that it is still unbearable, it is advantageous for the tree to discard the leaves during difficult times and spread the leaves for a suitable period. Trees that take such a strategy are called deciduous trees. Deciduous trees must bear a certain amount of resource consumption in order to make and discard leaves every year. Instead, you only have to hold the leaves when the conditions are good, so you can make thin and slightly wide leaves.
Relationship with climate
If it is tropical and humid throughout the year, a rainforest will be established. In areas where the dry season is strong to some extent even in the tropics, forests that shed leaves during the dry season and rain-green forests are established.
Looking from the tropics to the high latitudes, there is an evergreen broad-leaved forest that is smaller than the rainforest and has small leaves from the subtropical zone to the temperate zone. In colder areas, there are temperate deciduous broad-leaved forests. Beech forests are a typical example in Japan.
In colder areas, broad-leaved trees cannot grow and coniferous forests are established. Deciduous coniferous forests can also be formed in areas that are colder than evergreen coniferous forests. The larch forest corresponds to that.
Most of the plants that make up deciduous forests are deciduous. Deciduous trees generally have wide and thin leaves. Therefore, the forest under the deciduous forest is often brighter than the evergreen forest. Considerable light enters, especially from spring to early summer, when the leaves are not coming out or have not yet spread sufficiently. Aiming for this, the plant that blooms in spring, spreads its leaves until summer, and spends time underground is called spring ephemeral. However, in Japan, there are cases where beech forests are occupied by sasa, and spring ephemerals are not as many as in Europe.
Deciduous trees and deciduous forests
Deciduous forests consist of deciduous trees, but deciduous trees do not always grow in deciduous forests. For example, in laurel forests, there are many cases where some deciduous trees are mixed as constituent tree species. Deciduous trees tend to increase, as seen in satoyama, especially when human hands are involved. Pioneer plant species such as Zanthoxylum lanceolata, Mallotus japonicus, Clethra barbiner, and Stachyurus praecium are often deciduous.
Inubiwa and Mallotus japonicus are distributed south of central Honshu and do not exist in the deciduous forest zone. These are originally tropical flora, and probably have acquired deciduousness and advanced to the warm temperate zone. Also, these often do not fall in warm areas.