Effects and action mechanisms of increased light availability to understory Cinnamomum camphora seedlings
[Objective]This paper aims to reveal the effects of increased light on the growth of understory Cinnamomum camphora seedlings and to facilitate the regeneration of degraded natural secondary forest.[Method]The survival and growth of C.camphora seedlings were investigated with and without removing the Pleioblastus amarus in a degraded natural evergreen broad-leaf forest,and the physiological adaptation mechanisms of C.camphora seedlings to light intensity was also studied in a shade experiment.[Result]The removal of P.amarus had a significant effect on the survival and growth of the C.camphora seedlings under the forest.The survival of C.camphora seedlings increased from 16.67%to 63.89%when canopy openness increased from 2.36%±0.46%(control stand)to 11.37%±0.87%(P.amarus removed),and the growth of ground diameter(from 0.5 to 0.9 cm)and seedling height(from 0.16 to 0.63 m)increased as well.Under 30%-50%shading,the height growth of C.camphora seedlings was significantly higher than that in other treatments,while no significant difference was observed between 70%-90%shading and control.The number of leaves under 30%-70%shade treatments was significantly higher than that under control and 90%shade treatment.The area and thickness of leaves decreased with the increased shading,but the trend of specific leaf area was opposite.The leaf water content also increased with increased shading.And it changed in a stepped manner that it was significantly higher under 70%-90%shading than in other treatments with higher light availability.The contents of chlorophyll a and b in leaves of C.camphora seedlings generally increased under shading,but decreased when the shading intensity reached 90%.The chlorophyll a/b ratio was lower than other treatments when the shading intensity reached 70%and above.The maximum net photosynthetic rate and apparent quantum yield of C.camphora seedlings decreased gradually,and the light compensation point and dark respiration rate showed a downward trend,with some exceptions(70%shade).The light saturation point range was about 800-1 200 μmol·m-2·s-1without obvious trend.[Conclusion]In the degraded secondary evergreen broad-leaved forest with severe expansion of P.amarus,increased light availability by removing bamboo improve the survival and growth of C.camphora seedlings,which is conducive to the regeneration,quality and efficiency of the stands.Under mild and moderate shading,C.camphora seedlings are capable of adapting to light-restricted habitats by reducing investment to leaf structure,reducing maximum net photosynthetic capacity and increasing chlorophyll content.And intense shading will seriously inhibit the growth of C.camphora seedlings.According to the shading experiment,70%shading is the threshold of light availability limiting the growth of C.camphora seedlings.
NETL
NSTL
万方数据
