Chinese Journal of Agrometeorology

Distribution Patterns of Crop Phenology and Yield with Elevation and Slope Orientation in Ailao Mountain Area

Liu Yuhong Zhang Keying Ma Youxin Li Yourong (Institute of Ecology of Chinese Academy of Sciences, Kunming 650223)

1996, 17(06): .

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Based on the survey data from the eastern and western slopes of Ailao Mountain and the local climatic information, the distribution patterns of phenology and yield with elevation and slope orientation were analysed for crops grown in the area.

Studies on the Changing Patterns of CO_2 Concentration in Winter Wheat Canopy

Du Baohua Tong Chengfeng Yangping (Institute of Agrometeorology, Chinese Academy of Agricultural Sciences, Beijing, 100081)

1996, 17(06): .

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The distribution of CO 2 concentration and the effects of its reduction on wheat photosynthesis were analyzed using field-measured data. Following results were obtained: (1) In the daytime, CO 2 concentration was reduced in wheat field as a result of photosynthesis. The carbon dioxide from the atmosphere and soil surface was moved into the crop canopy and the lowest CO 2 concentration occurred where CO 2 flux was zero. During various developmental stages of wheat crop the lowest CO 2 concentration was always found in the segments of the plants with highest leaf area. (2) As shown by the CO 2 concentration isoplethic figures, there was a low concentration area between 9:00 and 18:00 on clear days (being 20～40μL/L lower than that measured 1 m above the crop canopy), and the center of which was located at 1/2 plant height. In this area, CO 2 concentration could be further reduced under conditions of weak wind and strong solar radiation. In addition, the gradients of CO 2 concentration near the ground level were steeper than in upper positions, which was produced by the CO 2 released from the soil.

The Grey-Markov Forecasting Model for Maize in Henan Province Based on the Periods of Yield

Chen Huailiang Zhang Xuefen Mao Liuxi (Meteorological Institute of Henan, Zhengzhou 450003)

1996, 17(06): .

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The grey-Markov forecasting model is suitable for the succession with large variations. In this paper, the concept of the periods of yield is put forward. The GM(1,1) grey model is applied to forecast the yield of maize in Henan Province. The transition possibility of Markov model is used for predicting the development direction of the system in the future and amending the GM(1,1) forecasted yield. The accuracy is improved by the simulation and forecasting.

Ecotypes and Growth Performance of Suitable Summer-sowing Varieties of Wheat in Northwest Plateau of Hebei Province

Cao Gungcai Wu Dongbing (Institute of Crop Breeding and Cultivation, CAAS, Beijing 100081) Fei Dao (Zhangjiakou Political Consultative Committee of Heber) Zhang Jinjing Wang Dongrui Li Xi Sun Qiuliang Li Jinrong (Zhangjiakou Bureau of Agricultu

1996, 17(06): .

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Experiments on Introduction and selection of summer-sowing varieties of wheat were conducted in northwest plateau of Hebei with an elevation of 1481.5m in 1994～1995. The results show that the ecological types of strong springness varieties (lines) are suitable summer-sowing ones among the 27 tested spring wheat varieties (lines). These varieties (lines) were sowed during the last 10 days of May and ripened in late August and early September. The main stems of these varieties possess only 6~7 blades. They do not need low temperature during the early growth and vernalization in the field. They have a high ecological adaptiveness to day-length and high temperature can promote their growth. At the 3 growing stages of sowing to jointing, jointing to heading, and heading to maturation, they show the characteristics of “short-short-long”. The rhythm for water requiment during the period of growth and development of these varieties coincides with that of natural precipitation. Summer-sowing wheat in cool areas of high latitude and high elevation with one crop per annum has a relatively high yield level and a high potential of yield increase. The development of summer-sowing wheat is one of the effective ways to increase the output of spring wheat.

Efficient Use of Light and Temperature Resources in Ecosystems of Crops and Fruit Trees Ⅰ.Measurement and Estimation of Light Penetration through Tree Crowns

Zhou Yunhua (Institute of Geograph, Chinese Academy of Sciences, Beijing 100101) Zhang Qiuying Zhang Xiaojie Ju Huiliang (Hebei University)

1996, 17(06): .

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Light (0.4～0.7μm) Penetration through individual peach, pear and apple tree crowns was measured with quantum sensors. Results from the 2-year experiment showed that for all the 3 fruit tree species and for normal years light penetration,τ d, can be expressed with an empirical formula, τ d= 7.85N -0.88, where N is the days counted from April 1. Varieties and ages of the trees have little impact on τ d. The effect of phenological stages on τ d can be removed by simply adjusting the formula according to phenological stages.

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