A Research For The Characteristics Of Canopy-air Temperature Difference With Time Variation And The Water-use Efficiency Of Tall Fescue Lawn

Water plays an important role in life, it also affect the species and distribution of plant of the earth’s surface. Water resources in North China’s is serious shortage, process research about water utilization efficiency (WUE) of plant leaves, and it’s mechanism in response to environmental factors, and the establishment of efficient water-saving irrigation system is the inevitable choice of these areas. In the May to December of2013in the garden of agricultural science and technology of Agricultural University of Hebei, Baoding City in Hebei Province, environmental factors were observed in real-time including t air temperature, air relative humidity, solar radiation, canopy net radiation, soil moisture, rainfall, wind speed, air saturation deficit on the lawn, the canopy-air temperature difference of the Tall fescue lawn conditions was calculated in the growth period of Tall fescue grass. This paper studied canopy-air temperature difference in different months, different weather conditions of diurnal variation; measured the stable carbon isotope composition of each month in Tall fescue grass (Stable carbon isotope ratio,δ13C), calculated utilization efficiency of water (water use efficiency, WUE) each month. Focus on the analysis of the environmental factors and soil moisture content on the turf canopy-air temperature difference and relationship between water use efficiency and response, and aims to provide a theoretical basis for solving the contradiction between water demand and supply, provide important guiding significance for water saving irrigation. The conclusions are as follows:(1)The canopy-air temperature difference of Tall fescue turf was negative in turf grasses establishment period of1day. After the influence of environmental factors, canopy-air temperature difference change process has obvious regularity on sunny days, reached the maximum at05:00, then decreased gradually, reaches a minimum at15:00, and then increases gradually. The canopy-air temperature daily variation on cloudy days is similar to sunny days, but the absolute value was significantly lower than that on sunny day, and the time valley value on cloudy days appeared delayed about2hours than sunny days. Canopy-air temperature difference on rainy days amplitude is not obvious, its value between-2℃to0℃.(2) Canopy-air temperature difference changed obviously and its values are below0℃on sunny days in each month in the growth of Tall fescue period. The time Canopy-air temperature difference value arived maximum value is07:00to08:00, and then canopy-air temperature difference became smaller, generally in14:00to15:00minimum and canopy-air temperature difference gradually become larger, more slowly increased to19:00. The best time to observe canopy-air temperature minimum value during the growth pired of Tall fescue is14:00to15:00.(3)The canopy-air temperature difference under the conditions of irrigation is less than no irrigation condition, the valley value appeared ahead of1hour, and canopy-air temperature difference value is larger.The analysis show that the influence of irrigation on the lawn to the canopy-air temperature difference is large.(4) In the whole growth period of Tall fescue turf, the δ13C values (%) and WUE (mmol C·mol1H2O) showed a more consistent trend, the values increased from June to July, decreased in August, increased September, then gradually decreased. Tall fescue leaf δ13C values changes at-30.5%o±0.11‰to-27.79‰±0.13%o, the mean value is-28.91‰±0.16%o. The highest value of Tall fescue turf δ13C values and the WUE appeared in September, respectively-27.78,19.37; the lowest value appeared in November, respectively-30.50,13.67.(5) The canopy-air temperature difference and environmental factors (air temperature, air relative humidity, solar radiation, canopy net radiation, soil moisture, wind speed, air saturation deficit) in the whole growth period of Tall fescue turf all of sunny days has relevance, the relevance from large to small basically is in trum:RH>VPD>Ta>W>Rn>Ra>SW-2>SW-1. Tall fescue turf canopy-air temperature difference significant in with RH and VPD correlation. The significant correlation with the air relative humidity remains significantly positive correlation at whole day, and the correlation coefficient of the day remained significantly negative correlation with air saturation deficit.(6) Tall fescue leaf δ13C values and sampling before the third day of the meteorological factors (air temperature, air relative humidity, solar radiation, air saturation deficit) has significant correlation, according to the size of Ta>VPD>Ra>RH. The WUE value and sampling before third days of the meteorological factors has significant correlation, according to the size of VPD>Ta>RH>Ra. The δ13C values and WUE and air temperature, solar radiation and vapor pressure deficit was positively correlated with relative humidity, and significant negative correlation between the air relative humidit.