| The impact of acid rain has become one of the global environmental problems,the harm ofacid rain to the forests is the hotpots of research on ecology. But there are still many problems inthe process of not clear about the role of the acid rain in China subtropical forest ecosystemdegradation and destruction. By taking Camellia sinensis and Quercus glauca seedlings ofsubtropical evergreen broadleaved forest species as the research object,setting severe acid rain（pH2.5）, moderate acid rain（pH4.0）,mild acid rain（pH5.6）and the study designs3different acidaction modes:（1）Acid rain is only leaching on the aboveground of seedlings;（2）Acid rain isonly directly input into the soil;（3）Acid rain is directly leaching on both the leaves and the soil.The blank control group. Plus a set of blank control group with equal parts water leaching.Through determination of seedling growth indicators（height and diameter）and the relativechlorophyll content and chlorophyll fluorescence parameters and the photosynthetic light responsecurves parameters and gas exchange parameters, Then through carrying systematical analysis andstatistical test, so as to reveal the direct effect, indirect effect,comprehensive effect of acid rain andthe control group to seedlings and their difference to elucidate the seedlings response mechanismto acid rain on Physiological Ecology, which can provide some referential theoretical basis forselecting anti-acid rain tree species, forest restoration,evaluating the damage of acid rain toforests.The results show that:（1）In a short-term, compared with the control group, direct effect of severe acid rainpromot the growth of Camellia sinensis seedlings height, indirect effects can promot growth ofdiameter. The comprehensive effect of moderate acid rain on relative chlorophyll content issignificant higher than the control group. The direct effect of Moderate and mild acid rain bothimproving the fluorescence parameters （Fv/Fm, Fv/Fo）. Under the comprehensive effect ofsevere acid rain, maximum net photosynthetic rate （Amax）was significantly higher than thecontrol group, but there was no significant difference between the direct effect, indirect effect, andthe comprehensive effect. under the direct effect and comprehensive effect of mild acid rain,maximum net photosynthetic rate (Amax) is significant greater than the control group and theindirect effect. （2）In a long-term, there is no significant difference on Camellia sinensis seedling growthindicators（height and diameter）under four different action modes. The comprehensive effect ofsevere acid rain had significantly improving the relative chlorophyll content; The direct effect andcomprehensive effect of mild acid rain both had significantly improving the relative chlorophyllcontent. Chlorophyll fluorescence parameters under four different action modes showed nosignificant difference. The indirect effect and comprehensive effect of severe acid rain and mildacid rain, maximum net photosynthetic rate（Amax）was significantly lower than the control group.（3）In a short-term, The direct effect of moderate acid rain can promote ground diametersignificantly of Quercus glauca seedlings. Under the indirect effect of severe acid rain on relativechlorophyll content is significant higher than direct effect,but there was no significant differencebetween indirect effect, the comprehensive effectand the control group. Under the direct effect ofsevere acid rain, the fluorescence parameters （Fv/Fm, Fv/Fo）are the lowest of the four differentaction modes. Under the direct effect of severe acid rain and mild acid rain, the maximum netphotosynthetic rate (Amax) is significant higher than the comprehensive effect, indirect effect andthe control group.（4）In a long-term, there is basically no significant difference on the growth indicators（height and diameter）under four different action modes. Under the indirect effect of moderateacid rain on relative chlorophyll content is significant lower than direct effect, the comprehensiveeffect, and the control group. Under the comprehensive effect of severe acid rain and moderateacid rain, the fluorescence parameters （Fv/Fm, Fv/Fo）are the lowest of the four different actionmodes and there is significant difference between the comprehensive effect and the control group.The direct effect, indirect effect,comprehensive effect of moderate acid rain and mild acid rain,there is no significant difference on the photosynthetic light response curves parameter. |
