Assessment of post-fire sprouting in oak species of the Zagros forests, Western Iran

Abstract

This study investigates the post-fire sprouting dynamics of three dominant oak species—Quercus brantii, Q. libani, and Q. infectoria—in the northern Zagros forests of western Iran. Sprouting responses were assessed at three post-fire intervals (2, 4, and 10 years), focusing on sprout origin (root vs. stump), sprout density, and growth performance of sprouts (height and diameter). The effects of stump diameter and species-specific traits on resprouting capacity were also evaluated. Findings revealed that root suckering was the predominant regeneration mechanism, contributing more than 90% of sprouts across all stands. Sprouting capacity remained relatively stable among different post-fire ages and oak species, showing no significant differences. In contrast, a strong negative relationship was observed between stump diameter and both sprout density and growth, with small to medium-sized stumps (5–35 cm) supporting the highest regeneration potential. Annual diameter and height increments were greatest in the early post-fire years (11.2 mm and 63.1 cm yr⁻¹ in 2AF stands) but declined significantly with stand age and increasing stump size, reflecting self-thinning and resource limitations. The largely uniform sprouting response across species highlights shared adaptive mechanisms such as persistent bud banks and robust root systems. Overall, the study demonstrates that root-derived vegetative sprouting—particularly from small to medium-sized stumps—constitutes the primary recovery pathway in fire-affected Zagros oaks, ensuring resilience where seed-based regeneration is limited. These findings emphasize the ecological importance of vegetative regeneration under recurrent disturbances and provide a basis for guiding post-fire management and restoration strategies in oak-dominated ecosystems. While these findings provide valuable baseline insights for guiding future forest restoration and management in fire-prone landscapes, their applicability remains geographically restricted to the Zagros region. Long-term monitoring will therefore be necessary to fully evaluate the success and persistence of post-fire regeneration dynamics.