[Effects of temporal and spatial variation of canopy structures and light conditions on population characteristics of Fargesia decurvata.]

The canopy structures and light conditions and the population characteristics of Fargesia decurvata, a dominant understory species, were investigated in three typical communities, i.e., deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest. The results showed that with the succession from deciduous broad-leaved forest to evergreen and deciduous broad-leaved mixed forest and to evergreen broad-leaved forest, the Shannon index, Simpson index and Pielou index were increased, suggesting that the development of communities in Jinfo Mountains tended to be stable. Moreover, canopy structures were significantly changed, in that the canopy openness and mean leaf angle decreased, leaf area index increased, and canopy extinction ability enhanced, resulting in the decrease of light intensity under the canopy. The upper canopy was the main contributor for canopy closure, with the crown depth and crown area of canopy being the two main influencing factors. Moreover, canopy structures were significantly correlated with light conditions in the forest, with the greatest influence on the diffuse solar radiation. With the growth season coming, canopy openness and understory light conditions were decreased, while leaf area index increased, and their maximum values appeared in June or July in the three forest types. The maximum and minimum value of mean leaf angle appeared in spring and summer, respectively. Clonal growth of F. decurvata was closely related to canopy structures and light conditions. In evergreen and deciduous broad-leaved mixed forest with moderate light, F. decurvata grew best, with high and thick ramets, high ramet density (29.69±1.68 ind·m-2) and high ability to expand rhizomes. In deciduous broad-leaved forest, the strong light condition caused the reduction of soil water might have effects on the growth of F. decurvata. However, in the evergreen broad-leaved forest with low light condition, ramets of F. decurvata tended to be short and thin, with low ramet density (5.80±1.16 ind·m-2) and the clonal expansion ability. Those results suggested that forest succession would change canopy structures and understory light conditions. Low understory light conditions prohibited the regeneration and development of F. decurvata population.