Studies On Phytomass Dynamics Of Poa Pratensis L.cv. QingHai Artificial Grassland And Cold Resistance In The Headwater Area Of Yangtze, Yellow And Lantsang Rivers

Studies on growth characteristics and phytomass dynamics of Poa Pratensis L.cv. QingHai artifical grassland. By adopting plant resistant cold physiology index to study cold resistance of four grasses which were P. Pratensis cv. QingHai, P. crymophilaL.cv.QingHai, Festuca sinensis Keng cv. QingHai and Bromus inermis in the artificial alpine meadow in the headwater area of Yangtze, Yellow and Lantsang Rivers. The mainly results are as follows:The growth characteristics of P. Pratensis cv. QingHai and it`s wild state were consistant after four years cultivated in the area of about 4000 m and growth duration was about 140 days .Aboveground growth of P.Pratensis cv. QingHai growed lowly from April to May, the growth fastigium was about from July to Autumn, the maximal height was 93.5 cm and P. Pratensis cv. QingHai didn't grow on September.The height curve was"S". The first peak value of net growth rate was in shooting stage at the middle of July and the second was in vegetative propagation stage at the middle of Autumn. The tillers of individual plant curve was"Logistic"and fit equcation was: y=25.9656/(1+3.2965e-0.338657x) (R2=0.9891,p<0.01). The first peak value of tillering speed appered before shooting stage and the second was in complete ripeness.The aboveground phytomass curve of P. Pratensis cv. QingHai was"Logistic"and fit equcation was: y=811.54/(1+2.7875e-0.827298x) (R2=0.9771,p<0.01); the accumulation of aboveground phytomass was in two main phases: from tillering to shooting stage and from heading period to complete ripeness. The first peak value of underground phytomass of P. Pratensis cv. QingHai appeared before fastigium of vegetative growth, and the second growth peak appeared after fastigium of vegetative growth of forage and underground phytomass increased at the end of September when nutrition matters transferred to soil before the above stopping growth. The main distribution of aboveground phytomass was under grass layers of about 0~50 cm, distribution of underground phytomass showed Inverse Pyramid Type and underground phytomass decreased with soil deepness increased.P. Pratensis cv. QingHai, P. crymophila cv.QingHai, F. sinensis cv. QingHai and B. inermis adapted to grow in harsh altiplano. The MDA contents of four forages were enhanced at differrent degree under chilling stress. MDA contents gain of P. Pratensis cv.