Effect of Fire Severity on the Species Diversity and Structure of a Temperate Forest in Northern Mexico

Abstract

Forests experience disturbances, such as fire, that affect their functioning, structure, and species composition. The objective of this work was to compare the species diversity and forest structure at sites affected by different degrees of fire severity, 9 years after a forest fire event. We used the differenced Normalized Burn Ratio (dNBR) index. Vegetation was sampled in three severity levels: high (HS), moderate (MS), and low (LS) and included the unburned (U) level as control. In addition, we calculated the species richness (S), the Shannon index (H), and the Evenness Index (E). The structural diversity of tree diameters and heights was measured applying the indices H, E, and the coefficient of variation (CV). The differences in the indices calculated across the fire severity levels were determined through analyses of variance (ANOVA) and Tukey’s multiple comparison tests. The results showed no significant differences (p ≤ 0.05) in the species diversity indices between fire severity levels. The structural diversity of tree diameters and heights was lower at the HS level. dNBR was negatively related to structural diversity; thus, it is concluded that HS tends to reduce structural variability in terms of diameter, height, and age. These results provide a baseline to understand how fire can modify forest structure and species diversity.

Keywords

• dNBR
• structural diversity
• intermediate disturbance hypothesis (IDH)
• forest response
• tree age structure
• fire disturbance