千岛湖次生林优势种植物光合生理生态特性

Abstract

The main factors that influence community succession in an evergreen broadleaf forest are differences in the ecological adaptability and eco-physiological traits of the various dominant plant species.Studies of the eco-physiological traits of these dominant species allow researchers to better understand the physiological demands and ecological traits of dominant species in their forest habitat and these studies also help researchers to recognize and understand the intrinsic mechanisms involved in forest regeneration and the mechanisms driving ecological succession in an evergreen broadleaf forest at the individual species level.In this study,we used a portable photosynthesis system to determine various physiological parameters associated with plant growth.We investigated the seasonal dynamics of the diurnal variations of photosynthesis,the responses to both light and CO2,and the relative chlorophyll content of the dominant plant species in the secondary forest surrounding Qiandao Lake,Zhejiang,China.The species included Pinus massoniana,Castanopsis sclerophylla,Lithocarpus glaber and Cyclobalanopsis glauca.The results showed the following.(1) Diurnal variations of the net photosynthesis rate(Pn) of P.massoniana exhibited a monomodal curve in all four seasons,while the variations in PnforC.sclerophylla were bimodal in August but had a single curve in the other three time seasons investigated.Diurnal variations of Pnof L.glaber and C.glauca exhibited a typical bimodal curve with obvious "midday depression"in May,August and November but had a monomodal curve in February.(2) The diurnal integral values of Pnof P.massoniana and C.sclerophylla were significantly higher in August than those in the other three seasons,while those of L.glaber and C.glauca were significantly higher in November than those in the other three time periods investigated.The average value of the diurnal integral value of Pnin the four dominant species differed significantly in all four seasons and was ranked in the order of:P.massoniana C.sclerophylla L.glaber C.glauca;(3) Compared with the other three dominant species,for P.massoniana,the light saturation point(LSP),light compensation point,maximum net photosynthetic rate,dark respiration rate(Rd),maximum rate of carboxylation and maximum rate of electron transport were highest in all four seasons,while the apparent quantum yield(AQY) was the lowest.The LSP and Rdof C.glauca were the lowest,while the AQY of C.glauca was the highest in the four seasons.Photosynthetic characteristics of C.sclerophylla and L.glaber were moderate among the four species.(4) In all four seasons,the relative chlorophyll content of C.glauca was the highest among the four dominant species,while that of P.massoniana was the lowest.All these results indicate that P.massoniana and C.sclerophylla are shade intolerant species and moderately shade intolerant species,respectively,while L.glaber and C.glauca are strongly shade tolerant species,although C.glauca is more strongly shade tolerant when compared with L.glaber.Based on these findings,we concluded that P.massoniana and C.sclerophylla will withdraw from the community during the succession.L.glaber and C.glauca will become the dominant species in the secondary forest surrounding Qiandao Lake as these forests mature.