Influence of tree size, local forest structure, topography, and soil resource availability on plantation growth in Qinghai Province, China

Although diversity-ecosystem functioning relationships have been extensively studied, the impact of forest structure on productivity and the main drivers of this relationship remain unresolved. In addition to forest structure, local abiotic conditions affect tree growth, by influencing the diversity of soil properties, but their relative importance remains unclear. We analysed how tree size, local forest structure, topography, and soil resource availability affect plantation growth and their relative importance. We investigated 6117 living trees in 64 plots in Qinghai Province and analysed individual growth responses of the main local afforestation species using mixed-effect models. Results indicated that tree growth was affected by tree size, local forest structure, topography, and soil resource availability to different degrees. Individual growth responses to local forest structure varied among species, especially in relation to size heterogeneity and spatial distribution. Local species diversity did not show significant complementarity or facilitation, but intense competition have occurred between trees. Tree size was the most important predictor of tree growth, and local forest structure was more important than topography and soil resource availability. These findings call for implementing appropriate management measures based on species traits and paying attention to changes in the relative importance of biological and abiotic factors with forest succession.