| The Huang-huai-hai plain is the main planting area of the winter wheat farmland and important commodity grain base, the research of water heat flux and energy balance about the farmland ecosystem is one of the hot spot of the currently research in terrestrial ecosystem and global change. This study used the observation experiment of eddy covariance system. The research object of this study is winter wheat farmland ecological system which located in the Feng-Qiu agricultural ecological experimental station of the Chinese academy of sciences in the Huang-huai-hai plain. Using the eddy covariance system, bowen ratio energy balance and total factor automatic meteorological station to carry out the continuous observation test, and analyzes the conventional meteorological observation data of nearly 50 years and agricultural meteorological data in the region. Divided the winter wheat growth and development into nine stages: seeding time, seedling emergence stage and tillering stage, over-wintering stage, regreening stage and jointing stage, heading stage and filling stage, mature stage, comprehensive application the methods such as eddy covariance method, bowen ratio energy balance method, correlation analysis, Morlet wavelet analysis methods, analysis the characteristics of farmland micro environmental meteorological factors in the winter wheat, water heat flux characteristics and characteristics of energy balance in various growth period of the winter wheat, and the effect of the different scales of environmental meteorological elements on the growth period of winter wheat and energy balance. Reveals water heat flux characteristics and characteristics of energy balance in each growth period of winter wheat farmland ecological system, to understand the huang-huai-hai plain farmland artificial vegetation ecological system- hydrological processes and mutual feedback mechanism, optimize the water thermal structure model, and to provide the scientific basis for evaluation the major grain-producing areas in the plain and water use efficiencyscientific and reasonable. The main conclusions are as follows:?1? The daily range of the temperature is large in heading stage of the winter wheat in huang-huai-hai plain, the night temperature is near 9 ?, temperature condition is advantageous to the large grain formation. The air temperature of heading stage and filling stage is significantly higher than other period, an average of 4 ? or so. The temperature daily range is the largest in mature stage, temperatures as high as nearly 38 ?, the average daily temperature is 26.1 ?, high temperature is benefied for winter wheat mature and harvest. The total rainfall is 174.4 mm in study period, compared with 357.8 mm which is the best water requirement of winter wheat in huang-huai-hai plain, is severity shortage, need irrigation.The rainfall in seedling stage can satisfy the requirement of the emergence of aswp. The precipitation is 22 mm in tillering stage, lack of water. Early winter stage almost no precipitation, after February precipitation is more, can meet the demand of wheat growth. In early turning-green precipitation is abundant, in late phase is shortage of precipitation; The precipitation in jointing stage, heading stage and filling stage is 35.9mm, 13.0 mm and 48.5 mm respectively, cannot meet the demand of the winter wheat earing, shall be carried out in the late spring stage, heading stage and filling stage irrigation timing. Every stage of growth and development of daily maximum relative humidity changed little, between 85% and 95%. The diurnal range of the relative humidity is the largest in tillering stage, the minimum is heading stage. Heading stage is highest about the 10 cm soil temperature in individual growth development period, over-wintering stage is minimum and diurnal range lowest, daily variation consistent with the change of the temperature, peak lags behind the temperature. Every stage of growth and development of the diurnal variation about the soil moisture content is very small, daily change rate is within 1%.?2? The climate change is with the temperature rise, rainfall, sunshine time decreases significantly as the main characteristics for nearly 50 years in the study area. Three different scales cycle existence in theannual average temperature: 3 to 5 years, 16 and 17 years and more than 30 years; there are two major cycle about annual precipitation: 4 to 6 years, 15 to 20 years; there are three major cycle about relative humidity: 5 to 8 years, 12-14 years, more than 30 years. In each growth period, the temperature change is bigger, about within 7?. The temperature of the seeding-tillering stage, over-wintering stage, green returned- jointing stage is rising trend, the speed of the rise, respectively is 0.13 ? / 10 a, 0.24 ? / 10 a,0.44 ? / 10 a. The turning-green stage to jointing stage?1989-2009? is obviously shorten of Feng-Qiu,which is significant relationship to the temperature have rise of this time period. In each growth period, the precipitation have a large variations. The precipitation is fluctuations in seeding time and tillering stage,and filling-mature stage. Precipitation in green returned stage and jointing stage are falling most obvious,which time is winter wheat growing period, and the spring drought severity, needs timely irrigation. The growth development period of sunshine hours is obviously reduced. The sunshine time fell most serious in over-wintering stage, rate of 11.411 d/a year.?3? Diurnal variation characteristics of the net radiation, sensible heat and latent heat are obvious in the growth period of the winter wheat, are basic in inverted "U" type curve, but the the peak and peak time is difference. During the whole period of winter wheat growth and development, the farmland ecosystem net radiation most used in latent heat, sensible heat and soil heat flux, the energy distribution different during each growing period, comprehensive affected by environmental factors and growing conditions, the energy distribution is different in each growth period. Before wintering period, peak net radiation and diurnal range is small. Green stage, jointing stage and filling stage, the net radiation increased gradually and reached high values, to grout- maturity, the net radiation reach maximum(760W.m-2). In the seedling the latent heat is only 40%, the proportion of latent heat is above 80%, the ratio of latent heat flux has fallen but still dominant in mature period, the other growth Period accounted for more than 55% in all. As thewinter wheat growth, the proportion of sensible heat flux in net radiation is a downward trend, the filling stage, mature period for a slightly higher. The proportion is highest in sowing time and seedling stage, more than 55%. After the tillering stage sensible heat flux are below 35%, the proportion in jointing stage,heading stage, the proportion is smallest only about 10%; so, the daily variation trend of the sensible heat flux and net radiation are basically identical before over-wintering stage.The soil heat flux difference between each growth and development is not obvious, the soil heat flux over-wintering stage are negative,the proportion of 15%. The rest period is near the zero value, positive during the day and night for the negative, are all below 10%.?4?At various stages, energy closed degree is high, the seedling stage is 83%, the tillering stage is90%, after regreening stage all more than 90%, seeding time, wintering period energy closure is low, 62%,67% respectively. This shows that in the farmland ecosystem of the study area, the observation data of eddy covariance system is accurate and reliable. In different growth period, different times of the day, energy closure degree is different. The relationship are significant between the micro environmental meteorological elements of winter wheat farmland and flux of each growth stage of winter wheat. The temperature and the flux is a highly positive correlation; Negative correlation relationship between relative humidity and the flux, the correlation is very strong. The relations, between soil temperature and soil heat flux is the positive, soil temperature and the net radiation; latent heat flux, sensible heat flux had no significant correlation; Soil moisture content between seeding time, green period and the flux is negative correlation, in other reproductive stage has no obvious correlation. |
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