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91.
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Xu Jun-liang Ma Lv-yi 《中国林学(英文版)》2007,9(4):251-255
In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalis and Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalis and Pinus tabulaeformis. But peak times and stopping times of sap flow varied con-siderably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalis and Pinus tabu-laeformis were about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized. 相似文献
94.
A split-root apparatus for examining the effects of hydraulic lift by trees on the water status of neighbouring crops 总被引:1,自引:0,他引:1
We describe a split-root system for examining the effects of hydraulic lift by trees on crop growth. In this system, upper
lateral tree roots were grown in a container set on the ground through which the taproot of the tree could penetrate into
the moist soil below. The container, with a radius of 0.5 m and a height of 0.20 m, consisted of two compartments divided
by a waterproof barrier. A markhamia tree (Markhamia lutea (Benth.) Schumann) and upland rice (Oryza sativa (L.)) plants were planted in one compartment, with only rice plants planted in the other compartment. Irrigation of the container
was ceased at the start of the experiment. The stomatal conductance of the rice plants in the associated side, in which both
trees and rice plants were grown, declined more rapidly during the first drying period than in the rice-only compartment,
suggesting that there was competition for water between the tree and the crop plants. However, during the later drying period,
the rice plants in the associated side were green and viable, while those in the rice-only side became desiccated. Rice roots
were seen intermingling with tree roots, and the soil water content in the associated site tended to be higher than in the
rice-only side. It is likely that hydraulic lift occurred in the associated side and that water that had been transferred
to the surface roots was released into the soil, enabling the rice plants in this compartment to remain viable. This novel
system is useful for examination of the effects of hydraulic lift by trees on the growth of neighbouring crops.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
95.
以阿拉伯胶和明胶为壁材的凝聚法生产茶油微胶囊的工艺过程及条件如下5%阿拉伯胶和5%明胶与一定量油茶籽油在60℃下乳化1min,在pH4.4下凝聚0.5h,10℃下固化1h,经离心和真空干燥即可.该法制备的微胶囊,有较高的含油率和包埋率.其粒径与凝聚时的搅拌速度密切相关,但其水溶性较差. 相似文献
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99.
原料表面碱液处理对稻草碎料板力学性能的影响 总被引:1,自引:0,他引:1
在实验室条件下探索了稻草原料表面碱液处理对稻草碎料板力学性能的影响.试验表明,处理后的稻草碎料板的内结合强度比处理前有大幅度提高,弯曲弹性模量和静曲强度比处理前则有所下降,但都达到了相关的国家标准;2h吸水厚度膨胀率升高,超过国家标准.因此稻草表面碱液处理提高了稻草原料表面润湿性和胶合强度,但对稻草碎料板的力学性能有影响. 相似文献
100.
Four populations representing the entire natural distribution range of Pinus brutia (Ten.) in Crete (Greece) were sampled to determine: (1) Altitudinal variation within populations of Lassithi, Vorizia, Koustagerako, and Samaria, and; (2) Longitudinal variation among the four populations, based on morphological and anatomical differences in cone, needle and seed characteristics. Samples were collected from 10 trees per altitude, at three altitudes in each population. A total of 12 morphological and anatomical traits from needles, cones and seeds were analyzed to assess the altitudinal and longitudinal variations of the species in the island. The number of teeth per cm showed significant (P<0.01) differences between altitudes in Samaria, Vorizia and Lassithi, while needle length, width and the number of resin canals showed significant differences (P<0.01) between altitudes in Koustagerako. Cone width showed patterns of variation along the altitudinal gradient in Koustagerako, Samaria and Vorizia. Most traits had their highest means at the middle altitudes (650masl) in all the four populations. Overall, no clear altitudinal differentiation was detected, probably due to high rate of gene flow. Longitudinal variability showed a clear pattern of differentiation along the east–west climatic gradient. Needle length, width, sheath length, number of teeth per cm and the number of resin canals were the most useful traits for determining the climatic gradient clines. 相似文献