Influence of Secondary Forest Gap Disturbance on Growth of Artificially Regenerated Phellodendron amurense Seedlings

The study investigated the impact of forest gap disturbance on the growth of Phellodendron amurense seedlings in artificial regeneration. It focused on 24 forest gaps of different sizes and Phellodendron amurense seedlings planted under the canopy in typical secondary forests in the Liaodong Mountains. The study measured the light intensity and its distribution at different points within the forest gaps, and evaluated the growth, morphology, and biomass accumulation of Phellodendron amurense seedlings planted in forest gaps of different sizes after 5 years (with those under the canopy serving as the control). This research provides a theoretical basis for the restoration of Phellodendron amurense, a precious and endangered tree species.The results showed that the survival rate of Phellodendron amurense seedlings in different light zones within the same gap was: medium light zone>strong light zone>weak light zone, and the survival rate in forest gaps of different sizes was: grade IV gap(84.06%)>grade III gap(82.09%)>grade II gap(79.9%)>grade I gap(64.8%)>under the forest canopy(38.14%). The height growth of seedlings in different light zones was: medium light zone>strong light zone> eak light zone>under the forest canopy. The average annual height growth of seedlings in forest gaps of different sizes was: grade IV gap(23.21cm/a)>grade III gap(15.73cm/a)>grade II gap (11.24cm/a)> grade I gap(9.8cm/a)> under the forest canopy(7.6cm/a). The ground diameter growth of seedlings in different light zones was: medium light zone>strong light zone>weak light zone>under the forest canopy. The average annual ground diameter growth of seedlings in forest gaps of different sizes was: grade IV gap(3.1mm/a)>grade III gap(2.02mm/a)>grade II gap(1.28mm/a)>grade I gap(1mm/a)>under the forest canopy (0.6mm/a). The height-to-ground diameter ratio of Phellodendron amurense seedlings in forest gaps of different sizes was: under the forest canopy(110)>grade I gap(99)>grade II gap(93.16)> grade III gap(85.2)>grade IV gap (81). The biomass allocation ratio of roots, stems, leaves and the whole plant was the largest in the medium light zone, followed by the strong light zone and the weak light zone. The root-to-shoot ratio decreased with the decrease of gap size, but the root-to-shoot ratio was relatively large under the forest canopy.