| Because all chlorofluorocarbons (CFCs), halons, carbon tetrachloride and other chemical pollution, ozone has drastically reduced the ozone layer becomes thinner. Thinning of the ozone layer will lead to increase ultraviolet B radiation when reaching the ground. UV stress is a big range, long-term impact, affecting production of terrestrial ecosystems and human life. The increase of human activities and extensive use of fossil fuels lead to emissions of a large number of sulfur, nitrogen compounds, causing acid rain, nitrogen deposition and other environmental stresses more and more serious Environmental stress affect the normal growth of plants, and exacerbating the imbalance in the ecosystem.The experimental site is located in Lin'an City, Zhejiang Province, the experiment selected four tree species, including Elaeocarpus, Schima ,camphor and Castanopsis . According to filter UVB, control, enhance UVB three gradient. simulated UVB stress, Experiments with ammonium nitrate NH4NO3 nitrogen deposition as a nitrogen source, were divided into control, low nitrogen, high nitrogen in the nitrogen and four processing gradient.The results showed that: (1) Other groups with L-UVB group compared to subjects ,evergreen broad leaf chlorophyll content is generally higher than the other two species. As time increases, the chlorophyll content of growth, especially in strengthening the UVB treatment group, significant increase of chlorophyll increased. The L-UVB group of chlorophyll content changes over time in different performance of different tree species Schima's chlorophyll content during the whole growth vary widely, and no significant difference between CK and UVB group of chlorophyll. Elaeocarpus and Camphor in L-UVB treatments in the early growth of chlorophyll did not change significantly, and the latter changed significantly. This shows that UVB radiation on plant species there are great differences in the sensitivity of some plant species. Some is more sensitive to the UVB radiation, and some types that they were affected by the incremental of UVB radiation is not obvious. Comparison of three different treatment plants found that UVB inhibited chlorophyll synthesis. For analysis of spectral reflectance of leaves on the Phase III trials, visible part of the spectral reflectance for the main differences concentrated in the red and green. At the same time, differences in the infrared significantly reduce. This place does not reflect changes of plants conditions in the UVB stress. Other parts of the difference is higher For evergreen broad spectral reflectance changes over time .The difference between the research results indicate that the spectral reflectance of three different treatments will be reduced in the May results show UVB increase or decrease ,and the rate of spectral reflectance change. In the August and November spectral reflectance of plant leaves reduce changes .In early "blue shift" occurred and in the late growth occurred "red shift", which may be leaf growth of plants, and plant ?s physiological changes adapt to the change of UVB.(2) The next results of simulated N deposition show that: Schima superba and Elaeocarpus in the low nitrogen and high nitrogen input grow better. Instead, the high nitrogen input change the inhibition for plant. Chlorophyll comparison results also verify this point; In the visible range can be more clearly seen that treatment to reduce nitrogen, but also shown as the red edge of the "red shift". Because nitrogen is the composition of chlorophyll .Nitrogen input can play on the effect of increasing the green. The results show for the characteristic bands that nitrogen and high nitrogen treatments with the other two have significant differences by the interaction analysis, there were significant about nitrogen deposition gradient and seasonal differences... |
PDF Full Text Request