Recolonization by Indigenous broadleaved species of a conifer plantation (Cupressus spp.) in Northern Iran after 25 years

Abstract

Abstract Key message A vegetation analysis revealed the extent of recolonization by native vegetation of a 25-year-old Cupressus spp. plantation in northern Iran. A young indigenous Quercus-Carpinus community replaced the conifers in the low-slope areas with deeper, heavier, and more fertile soils. Context Reforestation of degraded or clear-cut-harvested lands can modify site conditions, facilitating succession and reestablishing native forests. It is critical to investigate the plantation in terms of vegetation, natural regeneration, and environmental variables to better understand ecological restoration. Aims This study examines the recolonization of a Cypress plantation by native vegetation in the deforested Hyrcanian broadleaf forests and determines which edaphic, topographic, and structural variables are correlated to the degree of reconstitution. Methods A systematic random sampling method was used to establish 55 plots in a 25-year-old Cupressus plantation, followed by plot classification using TWINSPAN and environment-vegetation analysis using CCA. The classification groups were compared using an analysis of variance. Tested variables included floristic composition, stand structure, regeneration, topography, and soil parameters. Results Four vegetation groups were identified based on an analysis of floristic composition. The first group demonstrated the least degree of native forest reconstitution, as planted conifers (Cupressus spp.) were established alongside pioneer broadleaf shrubs, enhancing Zelkova carpinifolia (Pall.) K.Koch regeneration. While most conifers disappeared in the third group, Carpinus betulus L., Zelkova carpinifolia, and Quercus castaneifolia C.A. Mey became dominant. The most influential environmental factors in reestablishing indigenous communities were a low-slope, heavier soil with a higher organic carbon and potassium content. Conclusion On low-slope lands with fertile soils, the Hyrcanian native broadleaf forest can recolonize the coniferous plantation; however, on steep lands with poor sandy soils, planted Cupressus trees as well as relatively xerophytic shrubs in the understory may establish.