Difference between Responses of Potato Plant Height to Corrected FAO-56-recommended Crop Coefficient and Measured Crop Coefficient

This study was conducted to establish a simple convenient method for calculating crop coefficient, and provide a certain basis for the research of the empirical formula for calculating crop coefficient with plant height which could be measured conveniently with regional differences, especially for the establishment of accurate irrigation schedule of potato in Yunnan. By the field experiment on potato under the condition of drip irrigation, it was found that the models of plant height with corrected FAO-56-recommended K and measured K were a quartic polynomial and a cubic polynomial, respectively, and the polynomial of potato plant height with measured crop coefficient was simpler with higher degree of fitting; and the differences between the period with the highest change rate of potato plant height and the periods with the greatest FAO-56-recommended K and measured K exhibited a differences of 3 d. In conclusion： In the future study of simple or empirical formula calculation of crop coefficient, plant height should be considered as a main dependent variable in that the calculation result would be closer to the measured crop coefficient with the problem of regional difference existing in the FAO method solved and the formula might be simpler; and the irrigation time of potato should be 3 d earlier than the irrigation time determined according to the corrected FAO-56-recommended crop coefficient, especially in the key water requirement stages of potato.

Study on Species Diversity of Alpine Vegetation with Different Altitudes in Daban Mountain

[Objective] The aim of this study is to investigate species diversity of alpine vegetation in different altitudes of Daban mountain. [Method] Plant communities were surveyed in three different altitudes （3 025 m,3 405 m,3 813 m） of Daban mountain,the eastern Qilian,and the richness or diversity index of vegetation in three different altitudes was comparatively analyzed. [Result] The species richness decreased with the gradual increase of altitude,and species diversity of plant communities was relatively lower in medium altitude. Furthermore,community similarity also decreased with the increase of altitude,and β diversity of communities had a significant change. [Conclusion] Environmental factor change caused by different altitudes and human disturbance are important reasons for the change of species distribution pattern in different altitudes.

Modeling Hydrothermal Transfer Processes in Permafrost Regions of Qinghai-Tibet Plateau in China

Hydrothermal processes are key components in permafrost dynamics; these processes are integral to global wanning. In this study the coupled heat and mass transfer model for （CoupModel） the soil-plant-atmosphere-system is applied in high-altitude permafrost regions and to model hydrothermal transfer processes in freeze-thaw cycles. Measured meteorological forcing and soil and vegetation properties are used in the CoupModel for the period from January 1, 2009 to December 31, 2012 at the Tanggula observation site in the Qinghai-Tibet Plateau. A 24-h time step is used in the model simulation. The results show that the simulated soil temperature and water content, as well as the frozen depth compare well with the measured data. The coefficient of determination （R2） is 0.97 for the mean soil temperature and 0.73 for the mean soil water content, respectively. The simulated soil heat flux at a depth of 0-20 cm is also consistent with the monitored data. An analysis is performed on the simulated hydrothermal transfer processes from the deep soil layer to the upper one during the freezing and thawing period. At the beginning of the freezing period, the water in the deep soil layer moves upward to the freezing front and releases heat during the freezing process. When the soil layer is completely frozen, there are no vertical water ex- changes between the soil layers, and the heat exchange process is controlled by the vertical soil temperature gradient. During the thaw- ing period, the downward heat process becomes more active due to increased incoming shortwave radiation at the ground surface. The melt water is quickly dissolved in the soil, and the soil water movement only changes in the shallow soil layer. Subsequently, the model was used to provide an evaluation of the potential response of the active layer to different scenarios of initial water content and climate warming at the Tanggula site. The results reveal that the soil water content and the organic layer provide protection against active layer deepening in summer, so climate warming will cause the permafrost active layer to become deeoer and permafrost degradation.

植物工厂立体照明及其应用策略

人工光植物工厂可采用LED照明和无土栽培技术生产绝大多数农作物种类,包括低矮(叶菜、根菜等)和高大植株种类(工业大麻、甘草等)。人工光植物工厂通常采用传统的顶部光照的生产模式,但由于照射灯具及其照射方位固定单一,植物冠层截获的光照强度和光质固定(仅随植株大小或株龄变化),而且冠层上部叶片必然遮挡过滤来自上方的光辐射。经冠层上层叶片充分过滤吸收后,冠层下方叶片的光照强度的锐减,导致叶片光照不足,易衰老,削减了植株光合效率和高产潜力。针对上述问题作者提出了LED立体照明的观点。本文重点阐述了立体照明的定义、内涵和生物学原理,并以工业大麻为例提出了立体照明的应用策略。

Effects of Elevated CO_2 and Drought on Plant Physiology, Soil Carbon and Soil Enzyme Activities

Global climate models have indicated high probability of drought occurrences in the coming future decades due to the impacts of climate change caused by a mass release of CO2. Thus, climate change regarding elevated ambient CO2 and drought may consequently affect the growth of crops. In this study, plant physiology, soil carbon, and soil enzyme activities were measured to investigate the impacts of elevated C02 and drought stress on a Stagn[c Anthrosol planted with soybean （Glycine ma,z）. Treatments of two CO2 levels, three soil moisture levels, and two soil cover types were established. The results indicated that elevated CO2 and drought stress significantly affected plant physiology. The inhibition of plant physiology by drought stress was mediated via prompted photosynthesis and water use efficiency under elevated CO2 conditions. Elevated CO2 resulted in a longer retention time of dissolved organic carbon （DOC） in soil, probably by improving the soil water effectiveness for organic decomposition and mineralization. Drought stress significantly decreased C：N ratio and microbial biomass carbon （MBC）, but the interactive effects of drought stress and CO2 on them were not significant. Elevated CO2 induced an increase in invertase and catalase activities through stimulated plant root exudation. These results suggested that drought stress had significant negative impacts on plant physiology, soil carbon, and soil enzyme activities, whereas elevated CO2 and plant physiological feedbacks indirectly ameliorated these impacts.