| Artificial multi-layer forest as a unique forest stand structure, can satisfy the new requirement of sustainable development proposed for forestry, not only to make up the lack of a single forest management system, such as poor stability and loss of biological diversity, soil fertility decline, low stands productivity, easy to outbreak of diseases and insect pests, etc, but also have higher ecological benefits and economic benefits than single forest. In the multi-layer forest, due to the upper keep out of sunlight sun shade plants, understory light environment will have different degrees of impact, Light plays an important role on the growth and development of plants, physiological, biochemical, morphological structure of plants, etc. So changes in the light environment will tend to have a profound impact on the plant.In the subtropical climatic conditions of southern district in Guangxi, application of light environmental control technology, to create different upper densities in Pinus massoniana Lamb and Cinnamomum cassia Presl artificial multi-layer forest. With a fixed sample investigation and laboratory testing analysis techniques to research the growth, photosynthetic characteristics of Cinnamomum cassia and the difference of components in cinnamon oil. The main results were listed as follows:(1) In four different upper densities of multi-layer forest, when the upper canopy density of Pinus massoniana was 0.5 (treatment 3), the DBH, height growth of lower Cinnamomum cassia close to the pure plantation (full sunlight). However, the DBH, height growth in other treatments of multi-layer forest had different degrees decreasing. Showed that when the upper canopy density of Pinus massoniana was 0.5, the DBH and height growth of lower C. cassia had the best growth, that was the most appropriate upper stand density.(2) In each treatment condition, in addition to the leaf area of C. cassia in CK control significantly different to treatment 1,2 and 3, the leaf area, perimeter and ratio between of C. cassia in remaining treatments were not significantly difference. Under different conditions of light intensity, the leaf area of C. cassia in four kinds multi-layer forest were more than full sunlight conditions, indicating that C. cassia by increasing leaf area to increase the photosynthetic capacity. That morphological changes was conducive to get more light in low-light conditions, thereby enhancing the competitive advantage.(3) With the lowering of the upper canopy density, chlorophyll a, chlorophyll b, total chlorophyll of C. cassia leaf all exhibited increased after the first reduction, then further reduced. Chlorophyll a/b had a stable change among the treatments, only had significantly reduced in the upper canopy density of 0.5.(4) Addition to Gs, the C. cassia PAR, Pn and Tr were significantly changed in different upper canopy densities. With the decrease of upper canopy density the C. cassia PAR and Pn increased, indicating that C. cassia had the fastest accumulation of organic matter in the full light condition. In five kinds of lighting conditions, the C. cassia Tr and Gs showed similar trends, with the decrease of the upper canopy density showed increased and then decreased, increased again of the "N" type changes. The minimum value all appearing in the upper canopy density of 0.5. Meanwhile, the C. cassia WUE in the upper canopy density of 0.5 (Treatment 3) significantly higher than C. cassia pure plantation, and the LUE similar to pure plantation. That indicated that there was a moderate upper shade will help C. cassia improve the water use efficiency and the ability to use low light.(5) The overall oil yield of C. cassia in pure plantation was significantly higher than in multi-layer forest, showed that full light condition more conducive to the synthesis and accumulation of C. cassia oil. From various parts of C. cassia oil distribution, the leaf was relatively stable, while the oil yield of twig and bark fluctuated, which were manifested as CK had a maximum, the upper crown density of 0.5 followed. For the composition of C. cassia oil, Benzaldehyde, Phenylpropyl aldehyde, Cinnamaldehyde,2-Methoxy cimnamaldehyde and Cinnamyl acetate accounted for about 90% of the total, which were the main chemical ingredient of C. cassia oil. The content of Cinnamaldehyde had the better performance under the upper crown density of 0.5 in the various parts, and the proportion maintained a high level in bark and twig.Comprehensive the above analysis, concluded that when the upper canopy density of Pinus massoniana was 0.5, C. cassia had the optimal growth. |
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