Effects Of Simulated Acid Rain On Cryptomeria Fortunei Of Tianmu Mountain

Acid rain is the precipitation that pH value is below 5.6. Acid rain is widely distributed in southern China and does seriously harms to ecosystems. Tianmu Mountain Nature Reserve also suffers from the negative impacts of acid rain. In recent decades, ancient Cryptomeria fortunei forest, the most vegetation type in this area, has been declining since 1990's. A previous survey indicated that acid rain plays a critical role in the decline of C. fortunei. I conducted a series experiments on the effects of simulated rain on the C. fortunei and the aims are: (1) to reveal the response of C. fortunei to acid rain, from growth to physiology, (2) to know the changes of soil characteristics under treatments of simulated acid, and (3) to propose some suggestions about the restoration of C. fortunei.1. The moisture, buffer capacity and organic matter content of soil increase with the increase of altitude, while bulk density and pH value decrease. Total nitrogen content and total phosphorus content of soil have no clear trend.2. Under the stress of simulated acid rain, damage and necrosis were found on the leaves of seedling and the seedlings of pH1.5 were dead after three months' treatment. The height of seedlings is decreased by stress.3. The ultra structure of seedlings chlorophyll and mitochondrion were affected by simulated acid rain. Plasmolysises were detected in chlorophyll at first, then the outer membrane was damaged, at last, the thylakoids were accreted and even degraded. Meanwhile, the mitochondrial membrane were uneven, cristaes and slice structure were damaged in different degree. Totally, the damage of chlorophyll is more serious than that of mitochondrion during the same period and its damage types were more than those of mitochondria, too. The chlorophyll concentration of seedlings increased at first and then decreased.4. Under the stress of simulated acid rain, the antioxidase content were basically increased at first and decreased, but had no trend with the treatments of acid rain with pH 4.5, 2.5 and 1.5 of MDA and SOD, pH3.5 and 1.5 of POD and CAT. There were two main reasons. Firstly, the temperature in greenhous was much higher than outside in July and August. So the seedlings were affected by drought stress. Secondly, as we can see from the research result, the standard deviation of enzymatic activities was comparatively large, it maybe caused by the difference among individuals. Furthermore, researches on antioxidase are mainly focused on acute effect with a shorter period of time, but our study is a long-term pollution, so there maybe changes in seedlings during the experiment. 5. Under the stress of simulated acid rain, the pH values of soil under seedlings were decreased, but its buffer capacity was increased. Meanwhile, soil organic matter content and total phosphorus content had no distinct change, soil total nitrogen content was increased at first and then decreased, maybe some kinds of nitrogen were dissolved by the stress of simulated acid rain and soil total nitrogen content were increased, nitrogen was run off by the later period stress of simulated acid rain and the soil total nitrogen content decreased.