Soil respiration negatively correlated with volume gains by a young Pinus radiata clone over five months

It is assumed that greater plant productivity enhances autotrophic respiration (R_a). In a glasshouse trial using a one year old Pinus radiata D. Don clone selected for rapid growth, we examined the relationship between soil respiration, its components and tree growth rates over approximately five months. Soil respiration and R_a were significantly influenced by temperature; the response of heterotrophic respiration (R_h) approached significance. Soil moisture content had no effect on respiration. The productivity of individual clones, measured as volume increment, was not consistently positively correlated with soil respiration across the measurement intervals. Indeed, over the life of the trial it was found that individual tree volume increments were significantly negatively correlated with soil respiration. These results indicate that the most productive trees were associated with lower rates of autotrophic respiration, contradicting past studies. Further work is recommended to determine if this relationship holds true for these, and other, P. radiata clones in forest settings.