Effects of thinning on canopy structure, forest productivity, and productivity stability in mixed conifer-broadleaf...

Understanding the mechanisms whereby harvesting disturbance influences canopy structural complexity, forest productivity, and the stability of productivity is essential for the effective management and conservation of natural secondary forests. Previous research has established significant positive correlations among biodiversity, forest productivity and stability. Nevertheless, less is known regarding the processes whereby stand and canopy structures influence forest productivity and stability following harvesting disturbance. Because LiDAR systems are superior in acquiring information on forest canopy structure. In this study, we investigated the relationships among canopy structure, productivity, and stability of mixed conifer-broadleaf forest at 11 years post-thinning (2011-2022) (thinning intensity: int1 = 0 %, 0 %< int2 ≤20 %, 20 %< int3 ≤40 %, 40 %< int4 ≤60 %, int5 >60 %), utilizing field plot and LiDAR data. We quantified forest canopy structural complexity by calculating canopy entropy based on spatial point-cloud patterns. The results indicated that increasing thinning intensity significantly reduced canopy structural complexity and forest productivity (p < 0.05). However, the difference was not significant at thinning intensity less than 40 %. The structural equation model revealed that the indirect effects of thinning on forest productivity and stability, mediated through changes in density, forest height structural, dominant tree DBH, and canopy structural complexity, are greater than the direct effects. Moreover, density, dominant trees DBH, forest height structural, and canopy structural complexity are key drivers of forest productivity and stability. These findings elucidate the relationships among canopy structure, forest ecosystem productivity, and stability, and highlight the effects of thinning disturbance on these relationships. These insights will facilitate a deeper understanding of the interactions between structure and function in complex ecosystems and contribute to sustainable forest management.