Study On Leaf Gas Exchange And Chlorophyll Fluorescence In Pinus Massoniana Of Restoring Ecosystems In Changting County Of Fujian Province

As a special ecosystem, the ecological carrying capacity of granite mountainous area in subtropical regions is quite fragile. The problem of soil erosion caused by vegetation destruction increasingly conspicuous. So it is especially important to study the adaptation and responsion mechanisms of stress in soil erosion areas. To understand the mechanism of eco-physiological adaptation and response of plant species in Chingting Cuntry of Longyan region, Fujian Province, leaf gas exchange and chlorophyll fluorescence were examined, combining with microclimate and leaf water potential data, to investigate the characteristics of photosynthetic eco-phisiology of the pioneer species Pinus massoniana in three different restoring degree habitats.The results as followed:Pinus massoniana exhibited higher maximal values of Pn and LUE in high degree habitats than in low degree habitats (P＜0.01) .The diurnal curves of net photosynthetic rate (Pn) had two peaks. But the next one was indistinct. This phenomena indicated that Pinus massoniana had high adaptation mechanism. Under midday photosynthetic depression, Pinus massoniana can make use of photosynthetic active radiation in early morning in a rapid manner when environmental factors were appropriate. There were differences in the time and the value of the peaks occurred in two different restoring degree habitats. High degree habitat had high value of the peaks in Pn. The peaks occurred earlier in high degree habitat. The result explained the differences of the net primary production in different restoring degree habitats.Further studies were conducted on photosynthetic eco-physiological responses of Pinus massoniana to environmental stress. Both dynamic photoinhibition and chronic photoinhibition were experienced on the species. The results of three-way ANOVA and LSD multiple comparison on daily mean values of Fv/Fm revealed that different restoring degree habitats, different tree ages and different months all had significant differences. Chlorophyll fluorescence physiological process turned to more active state and weakened environmental stress coupling the advances of re-vegetation; Fv/Fm of seedlings, young trees and adult trees were gradually increased, indicated environmental adaption increased; Fv/Fm gradually increased in December, July and September.Primary discussion was also conducted on drought tolerance mechanism of Pinus massoniana. The result still showed high Pn ( 8.14μmol m^-2 s^-1) even when water potential was very low (-7.9 MPa), testifing that drought tolerance strategy was under the pioneer species. Both the values of non-photochemical quenching (NPQ) and dissipation (D) for Pinus massoniana were high, indicated that Pinus massoniana had high thermal dissipation to prevent photodamage in restoring ecosystems, Changting County of Fujian Province. But this high thermal dissipation depressed the growth of trees.The results revealed that Pinus massoniana had high adaptation in the restoring ecosystem of a granite mountain area in subtropical regions. Furthermore, our research primary explained the reason of vegetation hardly regeneration in restoring ecosystem of Changting county.