| With double reproductive advantages on sexual and asexual, Dicranopteris dichotoma hadextremely strong competitiveness and the repulsion force. And it often showed in the hydrophobic andpinus massoniana single optimal irrigation grass below a single optimal layer distribution. However, asthe starting by the pinus massoniana single optimal irrigation grass communities and succession ofevergreen broad-leaved forest community at last, Dicranopteris dichotoma began to present fadephenomenon. As a consequence, two assumptions were as follows.one was that shading by tall treesaffected, light became main environmental factors affecting the growth of Dicranopteris dichotomacontinuous intensive distribution.Another was some allelopathic substances of trees litter decompositionreleased inhibiting, had vital and ecological impacts on the growth of Dicranopteris dichotoma as asingle optimal.In order to investigate the effects of shading and littering for Dicranopteris dichotoma single layerdevelopment, this study, which set up four kinds of light intensity settings and selected four tkinds ofhighly representative objects of forest trees litter s a test of the donor, Potted Dicranopteris dichotomaas research materials, the research studies net photosynthetic rate, fluorescence parameters, pigmentcontent, reflectance spectroscopy, antioxidant enzyme activity, soluble protein and malondialdehydecontent indicators of Dicranopteris dichotoma. The main research conclusions were as follows.1. Under the condition of high temperature and strong lights from July to September, pottedDicranopteris dichotoma presented dead leaf spot, brown and dried up dead lastly.which showed that itwas not suitable for the growing of it under full light conditions.That Dicranopteris dichotomaresponsed to different shades of each treatment was mainly manifested in the demands of different lights.The Pn values of litter processing and the control group were maximum in the shading of50%.andDicranopteris dichotoma showed photoinhibition in the shade of80%and30%cover. The maximumvalue of Pn was Pinus massoniana under litter processing, and the minimum was Liquidambar litterprocess.Besides, the photosynthetic parameters were much lower in December, which indicated that theimpactions on Dicranopteris dichotoma were mainly in the differences in temperature and light intensity.Compared with October, the temperatures and light intensity were much lower andweaker in December.2. On the whole, under the three shade gradients, the regular of four kinds of fluorescenceparameters of litter processing performance was not obvious. Compared with October, every processing parameters in fluorescence were much more significant differences.in December, the Fv/Fm, Yield, ETRof Dicranopteris dichotoma were significantly lower than those in October, while NPQ was higher thanthat in October. The result of variance analysis showed that shading had a significant effect on thefluorescence parameters of Dicranopteris dichotoma.shading, litter cover and its its interaction witheach other had different influences on the different parameters of fluorescence.3. The ChlT, Chla, Chlb, Car content of Dicranopteris dichotoma were positively correlated withshade levels in the different degree. On the other hand, Chla/b was the opposite. The pigment contentmaximum was under the treatment of Masson pine litter, indicating that the treatment was good forpigment synthesis and promoting its photosynthesis under low light conditions.4. Under the various treatments, Dicranopteris dichotoma leaf reflectance spectral characteristicswere different rule, presenting trend of shade50%>30%shade>80%shade, which indicated thatshading differed the survival of small Dicranopteris environment. Masson pine litter treatment had themost siginificant effect on the trilateral parameters of Dicranopteris dichotoma.while diffrent shadingunder three different broadleaf litter treatments had different impacts on the trilateral parameters,basically the tendcy to increasing. Under the shading and leaf litter, Visible light and near infraredregion were sensitive areas of reflectance spectra.5. The antioxidant enzyme activity of Dicranopteris dichotoma leaves under shade degree ofreduction were presented with the rise after decling trend first, indicating that light intensity was one ofthe factors affecting its enzyme activity. When inhibited by light, it adjusted to a resistance to adversitystress. Masson pine litter treatment reduced the activity of POD, while SOD and CAT activities werepromoted. Three kinds of broad-leaved species litter processings weakened the antioxidant enzymeactivity of Dicranopteris dichotoma.6. Dicranopteris dichotoma soluble protein contents were increased with shade rate reduces,indicating that the light intensity was one of the factors affecting the soluble protein synthesis andaccumulation. And sclerophylla, pine and sweetgum litter treatments handled greater influence on MansDicranopteris dichotoma soluble protein. In October, Dicranopteris dichotoma MDA content waried inthe basic trends,50%shade>30%shade>80%shade. While in December, Dicranopteris dichotomaMDA content under pine, sweet gum, beech litter treatment was negative correlation with the degree ofshade. Under low temperatures of December, Dicranopteris dichotoma photosynthetic and physiologicalcharacteristics of response mechanism in weak light, allelochemicals double basically showed a trend ofdecrease under adversity stress, every adversity which reduced its photosynthetic and physiologicalparameters of the limiting factors were different. Low temperature stress had tne most siginificant onphotosynthesis, fluorescence parameters, antioxidant enzyme activity and soluble protein andmalondialdehyde, followed by weak light stress, and then was the litter matter releasing ofallelochemicals. |
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