杂花苜蓿与无芒雀麦混播群落种间竞争及稳定性

Interspecific Competition and Community Stability of Variegated Alfalfa+Awnless Brome Mixture

苜蓿(M ed icag o sa tiva)与无芒雀麦(B rom us innerm is)以0.3:0.7的播种量进行混播试验,测定组分种绝对生长率(AGR)、相对生长率(RGR)、相对产量总和(RYT)以及种间竞争率(CR),探讨不同苜蓿品种+无芒雀麦混播群落种间竞争及稳定性。结果表明:草地生物量的净积累主要在生育前期,单播和混播草地中杂花苜蓿的AGR和RGR平均值高于敖汉苜蓿(M.sa tiva CV.A ohan);同种苜蓿混播与单播草地生物量快速积累期相同,但不同品种间有所差异,敖汉苜蓿早于杂花苜蓿(M.varia M artin.CV.C aoyuan);苜蓿在孕蕾至初花期、无芒雀麦在拔节至抽穗期AGR和RGR最高,混播降低了苜蓿的AGR和RGR值;在组分频率下,春秋二季种间竞争小于种内竞争(RYT>1),而夏季种间竞争大于种内竞争(RYT<1),苜蓿的竞争力大于无芒雀麦(苜蓿的CR>1);甘农1号杂花苜蓿(M.variaM artin.CV.G annong N o.1)与无芒雀麦混播群落稳定性较好;在苜蓿+无芒雀麦混播群落中,光资源竞争是种间竞争的关键,温度对种间竞争有明显影响,夏季较高的温度减弱了无芒雀麦的竞争力,增强了苜蓿的竞争力;夏季是混播草地中无芒雀麦种群衰退的关键时期。

The constituent of cultivated mixed grassland is usually simple, with intensive interspecific competition, and community unstableness. An experiment on interspecific competition and community stability of a piece of cultivated grassland mixed sown with variegated alfalfa （Medicago varia） and awnless brome （Bromus inermis） of a ratio of 0.3：0.7 was conducted to determine the absolute growth rate （AGR）, relative growth rate （RGR）, relative yield total（RYT）, and interspecific competition rate（CR）. The experiment was performed at Tongliao,Inner Mongolia Autonomous Region , for three plant-growing seasons from 2003 to 2005. The net accumulation of the aboveground biomass occurred mainly in the plant early growth period （from 20th May to 9th July）. The AGR and RGR of both variegate alfalfa of monoculture and of mixed sown were higher than those of Aohan alfalfa （M. sativa, cv. Aohan）. For the same alfalfa variety, the fast biomass accumulation period of either that in monoculture or in mixture was very similar, while the fast biomass accumulation period of different varieties was variable. The AGR and RGR of alfalfa varieties were the highest during the period from the bud stage to the early flowering stage, while the highest AGR and RGR of awnless brome （B. inermis） occurred during the period from the elongation to the heading stage. Mix-sowing decreased the value of alfalfa＇s AGR and RGR. In spring and autumn seasons, RYT of the mixtures was greater than 1, indicating that interspecific competition was less intense than intraspecific competition. The competitiveness of Medicago was keener than that of awnless brome （Bromus inermis）（alfalfa CR〉I）. In the summer, there was sharp inter-specific competition in the mixture community （RYT〈I）. Competing for light resources was the conflict leading to interspecific competition, while temperature obviously provoked interspecific interfe-rence. The high temperature in summer curbed the competiveness of awnless brome （Bromus inermis） and stimulated that of alfalfa. Summer was the pivotal period of awnless brome when it declined in the mixture.