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The Temporal and Spatial Dynamics of Photosynthetically Active Radiation, Temperature and Relative Humidity in Maize Canopy

Author: QiHongYan
Tutor: ZhouGuangSheng
School: Chinese Academy of Meteorological Sciences
Course: Atmospheric Physics and Atmospheric Environment
Keywords: Corn Photosynthetically active radiation Temperature Relative humidity Extinction coefficient
CLC: S513
Type: Master's thesis
Year: 2008
Downloads: 245
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Abstract

With the accelerated process of urbanization, the available arable land resources in gradually reduced, which makes food security has become a major strategic issues, while using corn as the sustainability of bioenergy also mentioned on the national agenda corn by the people more and more attention due to the cultivation of a wide range of high yield advantages. Corn leaf when manufacturing organic matter through photosynthesis, canopy internal environmental factors, such as photosynthetic active radiation, temperature and relative humidity affect the net production of organic matter, thus an urgent need to understand the spatial distribution and dynamics of environmental factors in the canopy of maize growing characteristics. In this paper, Li-6400R photosynthesis system (Li-cor, Lincoln, NE, USA), photosynthetically active radiation within the canopy of maize growing in the China Meteorological Administration, Shenyang Institute of Atmospheric Environment Jinzhou Corn Agroecosystem Field Research Station , temperature and relative humidity measured dynamically, simultaneously determination of the different heights of corn leaves photosynthetic physiological ecology parameters and biological amount analysis of photosynthetically active radiation, temperature and relative humidity of the space distribution and temporal dynamics, to explore the Maize Population extinction coefficient of change characteristics, and build the the corn groups extinction coefficient model. The main conclusions are as follows: (1) photosynthetically active radiation in the canopy of maize growing between the different levels of attenuation rate is not the same, the Bill the model can be used only corn tasseling stage after noon. Photosynthetically active radiation within the canopy is not obvious vertical variation in the seedling stage, jointing stage vertical changes, and the attenuation of photosynthetically active radiation in the upper canopy larger than the middle and lower classes, in which the upper leaves absorb the total radiation about 80%; tasseling stage of the upper canopy leaves absorb 70% of the total radiation; up to 85% of the total radiation energy absorbed by the upper leaves in the canopy of the milk stage. The the corn maturity photosynthetically active radiation is mainly concentrated in the middle canopy height of about 120 cm above the leaves. Since the the corn tasseling period after, the lower canopy photosynthetic active radiation vertical distribution did not change significantly, the radiation intensity is also smaller. (2) canopy temperature varies with height showed small temperature vertical variation of the seedling stage; jointing stage before the 7:00 performance is less than the bottom of the canopy to the top of the canopy, and the crown layer at the top of the temperature rise is much higher than the bottom of the canopy, the maximum in around 13:00, and the rest of the time the temperature with a high degree of change is not obvious. Tasseling stage temperature in the morning and afternoon, and in the remaining time with the canopy height reduced, the temperature increase in turn. The the milky stage canopy temperature in the morning is the top level of the highest in the hierarchy, lower minimum, the remaining moments with the canopy height decreases from top to bottom a slight increase. Mature canopy temperature varies with height milky stage more similar, the main reason may be corn leaf blight caused. Daily temperature of different heights within the canopy dynamic performance for small changes in corn seedling and jointing stage performance tasseling stage after sunrise before sunset descending order from top to bottom, the maximum around 13:00 late in maximum photosynthetically active radiation; milky stage and mature daily temperature variations greater than 10 ℃. (3) canopy relative humidity vertical distribution in the seedling stage did not change significantly, while the morning in the jointing stage, the relative humidity was down from the decreasing trend above the canopy of the upper and lower canopy relative humidity of the middle to noon moment in the afternoon relative humidity vertical distribution did not change significantly; tasseling stage relative humidity in the morning was the first increases and then decreases variation, the gradual increase in the remaining moments with canopy height reduction, close to the surface reaches a maximum. Milky stage the relative humidity in the morning with the canopy height decrease, while the remaining time relative humidity can be reduced with the reducing of the canopy height. The relative humidity of the mature canopy temperature significantly, both were anti-phase changes, reduced height decreases with the canopy. Relative humidity daily performance of dynamic seedling stage was sooner or later the low and high features, jointing stage at noon for the morning and evening high and low noon; tasseling stage showing a standard \maximum of 84% around 8:00, and then decreases up to the minimum value, about 35% of the diurnal variation in the range of 50% fluctuations in 16:00; mature canopy relative humidity showed the first increase then decreases, additional features, up to maximum of 79% at 9:00, around 14:00 in the afternoon to reach the minimum 27%. (4) A maximum of photosynthetically active radiation in maize growing mostly occurred around 11:00, the maximum temperature occurs mostly around 13:00 lags behind the photosynthetically active radiation, but after tasseling stage, the relative humidity is affected by temperature the impact is more obvious, was the anti-phase variation. (5) corn population extinction coefficient has the daily dynamic characteristics, for the morning and evening high noon characteristics of low, but the change is not obvious in the tasseling stage. Small leaf area index, built Maize Population extinction coefficient model is superior to the Norman model. When the sun is located noon (solar elevation angle greater than 75 °), the extinction coefficient and leaf area index showed a significant parabolic relationship. Corn groups including the solar elevation angle and leaf area index extinction coefficient model is significantly better than the Norman the model.

The Temporal and Spatial Dynamics of Photosynthetically Active Radiation, Temperature and Relative Humidity in Maize Canopy

Abstract

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