Influence of soil qualities on intra- and interspecific competition dynamics of Larix kaempferi and L. olgensis

Abstract

Forest management has potential to detrimentally impact long-term plantation productivity. Establishment of mixed plantations and fertilization are two important management approaches when trying to maintain soil qualities and productivity. In this study, two types of experiments were conducted to investigate the influence of soil qualities on intra- and interspecific competition dynamics in two larch species. Experiment 1: We transplanted two deciduous larch species, Larix kaempferi and L. olgensis, to study intra- and interspecific competition dynamics in two different types of soil: one from a c. twenty years old L. kaempferi plantation (named larch soil) and another from a secondary natural forest (named mixed-forest soil). Experiment 2: Effects of N fertilization on the competition dynamics of the two larch species were tested in the larch soil. In the experiment 1, we hypothesized that the growth of L. kaempferi in the larch soil under no fertilization is inhibited when competing with L. olgensis, and their competition relationships may be different in the mixed-forest soil. In both species, the starch and TNC (total non-structural carbohydrate) concentrations of roots and shoots were significantly higher in the mixed-forest soil when compared to the concentrations in the larch soil without N fertilization (N−). The relative competition intensity (RCI) was affected by the soil type. RCI of L. olgensis was higher than that of L. kaempferi in the larch soil N- condition, and RCI of L. kaempferi was higher than that of L. olgensis in the mixed-forest soil in 2015. However, the RCI values did not show significant differences in 2014. In the experiment 2, L. kaempferi showed superior competitiveness in the larch soil N+ condition, with the highest RCI value in 2014, but the RCI value of L. kaempferi declined while the RCI value of L. olgensis increased from 2014 to 2015. Both experiments indicated that the benefiting species had higher element (C, N and P) and non-structural carbohydrate (starch and soluble sugar) content accumulation ratios from 2014 to 2015. We found that competition relationships changed between years and depending on conditions. We suggest that mixed plantations and N fertilization together could effectively promote the productivity of Larix.