The effect of altitude above sea level on some structural characteristics, dynamics and diversity on Zagros forests in western Iran

Abstract

Abstract Ecological conditions, such as environmental gradients, can affect the structural features and diversity of forests situated in altitude gradients. A study was conducted to examine the impact of altitude above sea level on certain structural features and diversity in Zagros forests in the Ghalajeh area of Kermanshah province. To analyze the effects of diversity on structural and habitat characteristics and their changes in different altitude gradients, eight sites were selected in four altitude ranges from sea level: 1200–1475 meters (low-land), 1475–1750 meters (low to mid-altitude), 1750–2025 meters (mid to high-altitude), and 2025–2300 meters (high-land), identified in both northern and southern slopes. In each site, three sample plots were chosen as replicates, and within each sample plot, all necessary characteristics of trees were measured. The results showed that with increasing altitude above sea level, the number and frequency of tree species increased, while the density of Iranian oak trees decreased. Species such as Almond tree (Prunus elaeagrifolia), Italian Honeysuckle (Lonicera nummulariifolia), and Maple tree (Acer monospessulanum) were predominantly present at higher altitudes. However, the presence of trees initially increased (in the mid-altitude elevation), then decreased (in the highland elevation) with increasing altitude, although this attribute was nearly equal in the lowland elevation in both northern and southern slopes. The study also found statistically significant differences (p < 0.05) in variables such as tree diameter at breast height, tree height, and tree dieback levels across different altitudes above sea level. These results are beneficial in addressing ecological issues such as forest conservation and management, as well as assessing favorable environmental conditions, providing insights to predict future trends based on these findings.