| The problem of how to scientifically utilize for limited water resources and meliorate ecology and environment continually are urgent requirement for important project currently. From March to November,2002, the field experiment was carried out in Clover Experimental Station(3934'N, 11628'E;elevation 50m) of Clover Group,which is located in Chaoyang District, Beijing ,with an accumulated temperature of 4200℃ above 10℃ and an annual precipition of 600mm .Perennial ryegrass,Kentucky bluegrass and tall fescue were used and drilled on April 28,2002,with 3 cm in depth and 20g m-2 in sowing quantity. Three moisture gradients(30%-50%FC,50%-70%FC,70%-90%FC) were arranged in different rectangular plots of 4m X 5m for every specie, with 0.5m isolation between plots.Irrigation amount was calculated according to different soil moisture treatment. The measured depth of soil moisture was from 0 to 30cm.The soil moisture was measured with drilling method and by the tensiometer instrument in the interval Of 5 cm once every ten days. The irrigation amount of the plots could be calculated using the following equation: 1= P (W2-W1) h. In this equation , I is the supplement of irrigation; p is the measured bulk density of soil in the experimental field;h is the measured soil thickness; W2 is upper value of three treatment grades; W1 is the water content of soil by weigt.The observation items including:(1)regeneration speed.(2)aboveground biomass (including fresh and dry weight):which were sampled in a 25cm X 25cm sample square every 7-10 days with 3 duplications.(3)underground biomass(dry weight): which were cored every 10 cm soil layer totaled 30 cm with 4.4cm diameter implement every month with 6 duplications.(4)transpiration and water use efficiency: which were studied with BAU Portable Photosynthesis System.(5)turfgrass quality.According to the experimental data,the responses of morphological characteristics of three kinds of cool-season turfgrass were studied. The results obtained are as follows:(l)In the treatment with different soil moistures, while increasing soil moisturecontent, growth rate and stem dry weight of three kinds of cool-season turfgrass increased gradually, but the difference between soil relative moisture of 50%-70%FC and 70%-90%FC was not remarkable.(2)Biomass allocation was significantly influenced by the water gradient.About 73.4%~92.2% roots distributed within the top 10 cm soil. Most roots distributed downwards in low water gradient, and distributed upwards in high water gradient, while increasing soil moisture content, underground biomass and aboveground biomass competed with each other. In treatment with soil relative moisture of 50%-70%FC ,both the top 10 cm soil roots and the 30 cm soil roots increased simultaneously.When the moisture gradient was 30%~50%FC, underground-biomass perpendicular allocation ratio in the soil layer of the top 10cm,between 10cm and 20cm and from 20cm to 30cm was 73.4%~89.5%,7.3%~16.8%, 2.7%~9.8% respectively; the moisture gradient was50%~70%FC,the ratio of each soil layer was 79.5%~-91.6%, 6.6%~ 13.6%, 1.7%~6.9% respectively; when the moisture gradient was 70%~90% FC, the ratio of every soil layer was 78.3%?2.2%,5.1%~14.2%,2.0%~6.0%.(3)The quantity and rate of water consumption were compared and analyzed in different water gradients. The results showed that different species had different water consumption in the same water status. Under the low water gradient, the water consumption of all the species decreased, but it increased the water use efficiency and otherwise decreased turfgrass quality.(4)Anova analysis showed that turfgrass quality was influenced remarkably by the water gradient. But when soil moisture content was about 50%-70%FC,turfgrass quality of the three species were all ideal(scored>6.5). Under the moisture of 30%-50%FC, Kentucky bluegrass(score=5.8) and perennial ryegrass(score=6.2) are not fit to the taste of all. But tall fescue still showed ideal properties.(5) The optimum soil moisture content is 50%-70%FC.
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