Search

The smoke tree (Cotinus coggygria Scop.) is not only an important ornamental tree that changes the color of its leaves in autumn but also maintains red juvenile leaves on vigorous sprouting shoots. To elucidate the process of leaf reddening in the smoke tree, we examined the structure and function of its leaf venation system, anthocyanin levels, leaf water conservation ability in red juvenile leaves and green mature leaves, leaf temperature, stomata conductance and snap strength of petiole. A combination of thermography, image analyses and photosynthetic measuring technology was used to study the facts of leaf reddening of smoke tree. We found that spatial and temporal heterogeneity in the pattern of leaf reddening in the smoke tree illustrates the interaction between internal metabolism and environmental factors. These results indicate that there are periods that show water and energy imbalances at leaf lamina and that this phenomenon is essential to leaf reddening, especially during periods of leaf expanding and leaf shedding. We consistently observed a relationship between high temperatures and leaf reddening, which indicates the latter is a photoprotective response induced by imbalances in water and energy.

Thermography has been used in many fields to perform non-invasive temperature measurements of natural objects. In this paper, thermography was used to determine the temperature of leaves, stems and branch kerfs of Japanese spindle (Euonymus japonicus Thunb.) and glossy privet (Ligustrum lucidum Ait.) in the city of Jinan in China during winter. The temperatures of the leaves, stems and branch kerfs were monitored as the temperature decreased after the sample was subjected to hand heating or after the branch was cut. Differences in the specific heats and the latent heats of the leaves, branches and stems with different water contents and transpiration capacities were confirmed. The significant temperature difference obtained after hand heating between different leaf sections with varied water contents made it easy to obtain the thermal images, which were clear and exhibited reduced systematic errors. After hand heating, a significantly higher temperature was found at the major vein system of both Japanese spindle and glossy privet. This increased temperature difference made it possible to detect the water and the thermal state of these leaves. Therefore, it was possible to detect scorched area of the leaves, the twig dieback and the sap warming phenomenon in the leaves using thermography. In addition, the leaf bending phenomenon observed in Japanese spindle leaves during the deep freezing process indicates that the leaf scorch symptoms result from water stress and a lack of sap warming.

The spatial distribution and characteristics of fine roots (< 2 mm in diameter), and rhizosphere soil properties were studied in a mixed planted forest of black locust ( L.) and velvet ash ( Torr.) 27 years after planting in a coastal saline soil of the Yellow River delta, China. The results of fine root analysis showed that the fine roots of both black locust and velvet ash were mainly distributed in the soil layer at 0â20 cm depth and 50â150 cm from trees. The fine root distribution of both species suggests a strategy of avoiding salinity rather than salt âtolerance. The horizontal spread distance of fine roots of velvet ash was evidently longer than that of black locust. The fine root biomass, specific root length, specific root area, specific root volume and root activity were significantly higher for velvet ash in comparison with black locust. The results of soil analysis showed that rhizosphere soil pH of black locust and velvet ash were significantly lower compared with non-rhizosphere soil. The available N content in rhizosphere soil of black locust was higher than that of velvet ash. However, the contents of soluble salt, organic matter, available P and available K in rhizosphere soil of velvet ash were higher than those of black locust. The above results indicated that the differences between black locust and velvet ash in fine root distribution, characteristics and rhizosphere soil properties were the major reasons for that velvet ash showed stronger acclimation responses than black locust to the coastal saline soil.Robinia pseudoacaciaFraxinus velutina

At present the environment in Yellow River delta region is particularly badly eroded. In view of the situation, use of vegetation for environmental protection is most effective. In order to select suitable tree species, some physiological parameters such as proline content, ratio of bound water and free water, relative conductivity of leaves were applied to this experiment to probe the capability of trees to resist salinity stress. Based on the testing results, these tree species such as R. hispida, F. velutina, C. korshinskii, N. sibirica, T. chinensis, R. typhina, S. matsudana, A. fruticosa and A. altissima were chosen and planted in the area. The result of stand inventory implemented in the year showed that these trees grew well, especially for L. chinense, the biggest height increment reached 1.73 m, and the mean was 1.45 m; and the biggest basal diameter was 1.52 cm, the mean was 1.21 cm. Hence it was concluded that planting trees could prevent soils from salinization and protect lands from degradation.