The effects of cover crown, percentage and slope aspect on the quantitative distribution of the Alders saplings in forests of north of Iran

摘要

Alder (Alnus subcordata) allocates itself to the 7.6% of Iran's northern forests and after the Beech, Hornbeam and Oak, is the fourth commercial tree of Iran. This tree is aborigine of northern parts of Iran and with itself and in a mixed form with the other tree species, forms a varied forest community. The Alder is a pioneer species, establishes in an open area of the forest, because it likes more lightness to producing a huge quantity of seeds yearly. It is playing an active role in nitrogen fixation which can improves soil fertility also. The importance of the Alder is related to its role in regeneration processes of ruined forests and using them for re-plantation. The studied area was a part of Tonekabon's forest, covered with species like hornbeam, the Alder and Maple. In this study, the quantitative situation of the Alder's regeneration in the different cover crowns (30 to 40, 50 to 60 and 70 to 80%), slope percentages (0 to 20, 30 to 50%) and slope direction (northern, southern, eastern and western directions) were studied in a factorial experiment using complete randomized block design with four replications. In 72 chosen plots, the quantitative situation and regeneration establishments of the trees having height of more than 1.3 m or less were studied, and the collected data being analyzed using SPSS software. The results showed that, the Alder regeneration in the most humid places (north) and least slope (0 to 20%) consisted of more frequency in comparison with the western and eastern slope directions with more slope (30 to 50%). In addition, with decrease in cover crown percentage, the frequencies of the Alder's saplings were also being increased.