Studies On Eco-physiological Characteristics And Interspecific Relationship For Forages Of Different Patterns Of Legume-grass Mixture Grassland

The artificial grassland which was established by mixing leguminous and gramineous forage can make full use of natural resources, show the forage production potential, improve forage quality, and the grassland ecological stability. In this study,4 forage species which included Agropyron mongolicum-Bromus inermis Leyss、Psathyrostachys Nevski and Astragalus adsurgens were selected. The artificial grasslands which were established by mixing Agropyron mongolicum+Bromus inermis Leys+Astragalus adsurgens (H1)、Agropyron mongolicum+Psathyrostachys Nevski +Astragalus adsurgens (H2)、Bromus inermis Leyss+Psathyrostachys Nevski+Astragalus adsurgens (H3) Agropyron mongolicum+Bromus inermis Leys+Psathyrostachys Nevski+Astragalus adsurgens (H4) and with only one species. By studying emergence rate, the growth rate, biomass, diurnal changes of Photosynthetic physiology,interspecific competition of different kinds of forages under different patterns of legume-grass mixture grassland, the ideal mixed combination were determined. The main conclusions are as follows:(1) Different patterns of Legumes-grasses mixture promoted emergence and tillering of gramineous and leguminous forage, especially Bromus inermis Leyss+PsathyrostachysNevski +Astragalus adsurgens mixed combination significantly improved forage seedling rate and tiller number.(2) Under different patterns of legume-grass mixture grassland, the growth rate of various forages showed upward-downward trends. Grasses grew fastest at 55-75d period, while legumes at 45-65d period. The growth rate of each forage species under mixture patterns were significantly higher than those of single patterns, especially that of Bromus inermis+Psathyrostachys nevski+Astragalus adsurgens were the highest throughout the growing season.(3) The grassland yields showed increase-decrease trends under different sowing patterns with a continuation of the growth period. The biomass accumulated rapidly from July 25 to September 5. The yields of different mixture grasslands were higher than those of single grassland during the whole growth period, especially of which Bromus inermis+Psathyrostachys nevski+Astragalus adsurgens combinations. The underground biomasses of each single grasslands were lower than those of mixture grasslands except for Bromus inermis single grassland.(4) Under different patterns of legume-grass mixture grassland, net photosynthetic rate (Pn) conductance (Gs), transpirations rate (Tr) and photosynthetic water use efficiency (WUE) of various forages showed bimodal curve, peaking at 10:00-11:00 and 13:00-14:00 respectively. Net photosynthetic rate (Pn), conductance (Gs) and photosynthetic water use efficiency (WUE) were higher in H3 combination, while transpirations rate (Tr) is lower in H3 combination. Intercellular CO2 concentration(Ci) among of various forages showed "U" shaped curves, and the lowest values appeared at 13:00-14:00. Net photosynthetic rate (Pn) and photosynthetic water use efficiency (WUE) of legume-grasse mixture grasslands were higher than those of single grasslands, especially of which Bromus inermis Leyss+Psathyrostachys Nevski+Astragalus adsurgens combinations.(5) Under different patterns of legume-grass mixture grassland, both gramineous and leguminous forage enhanced competitiveness for resources, and had yield advantages than those of single grassland. RDg、RD1 and RYT of different mixture grasslands were significantly above 1 at different growth period. Especially Bromus inermis Leyss+Psathyrostachys Nevski+Astragalus adsurgens combination can effectively promote forage germination, tillering and biomass accumulation.(6) The competitive pressures of grasses of under different mixture combinations mainly came from interior, which had advantages in the competition. The interspecific competitions of legumes were greater than intraspecific competition. The CRh values of grass species were significantly above 1, while the CRd values of legume species were all below 1.(7) Comprehensively considering the seedling emergence, tillering, growth rate, biomass, photosynthetic characteristics, competition coefficients and other index, Bromus inermis+Psathyrostachys Nevski+ adsurgens combination is ideal for artificial grassland establishment.