Developing mixed-effects height-diameter model using stand and environmental factors for mixed forests in northern...

Area of Science:

• Forest Ecology
• Allometry
• Quantitative Silviculture

Background:

• The tree height (H)-diameter at breast height (D) allometric relationship is fundamental for forest biomass and carbon stock estimations.
• Environmental factors and species diversity are known to influence H-D relationships but are often understudied in model development.

Purpose of the Study:

• To develop an environment-sensitive nonlinear mixed-effects model for the H-D relationship in Hulunbuir mixed forests.
• To investigate the influence of stand attributes, soil properties, climate, and species diversity on H-D scaling.

Main Methods:

• Collected data from 99 forest plots in Inner Mongolia, China.
• Developed a nonlinear mixed-effects model incorporating stand-level, soil, climate, and diversity variables.
• Accounted for variations at plot and species levels using random components.

Main Results:

• Quadratic mean diameter, basal area (BAL), Simpson's diversity index (SIM), mean annual precipitation (MAP), and soil organic carbon significantly impacted the H-D relationship.
• Height growth increased with BAL and MAP, but decreased with higher SIM.
• Species traits and environmental factors were found to jointly influence H-D scaling.

Conclusions:

• The developed model provides a more accurate estimation of tree dimensions by integrating environmental sensitivity.
• Findings support adaptive forest management strategies in response to environmental changes.
• Highlights the importance of considering species diversity and environmental factors in allometric modeling.