【摘要】 为了研究施氮对不同草地植物生物量及其分配的影响,以及温带草地生态系统碳交换过程对氮素的响应,在内蒙古太仆寺旗农田-草地生态系统野外站,以4种草地植物:紫花苜蓿(Medicago sativa L.)、高丹草(Sorghum bicolor L.)、羊草(Leymuschinensis T.)和小叶锦鸡儿(Caragana microphylia L.)为材料,进行了3种氮素水平[对照、中氮(30 gN/m2)和高氮(60 gN/m2)]的盆栽控制实验。研究结果表明:施氮显著促进了4种植物地上生物量的积累,紫花苜蓿在中氮水平地上生物量最大,较对照增加了24.8%,高丹草、羊草、小叶锦鸡儿在高氮水平地上生物量最大,分别较对照增加了45.6%、39.3%和72.2%。4种植物在中氮水平地下生物量最大,而细根(直径≤2mm)生物量随施氮量的增加显著减少。羊草根茎生物量及其分配比例随施氮量的增加而增大。施氮显著降低了4种植物的根冠比,紫花苜蓿的根冠比在中氮水平时最小,为1.62,高丹草、羊草、小叶锦鸡儿的根冠比在高氮水平时最小,分别为0.57、1.02和0.41。随施氮量的增加,植物地下部分特别是细根的分配比例显著降低,地上部分分配比例显著增加。不同植物对施氮水平的响应不同,相比豆科植物,施氮显著促进禾本科植物生物量积累,并使其生物量分配格局发生显著改变。更多还原

【Abstract】 In order to study the effects of nitrogen fertilizing on the biomass and its allocation of different grassland plants and thus on the carbon exchange in temperate grassland ecosystem,potted control experiments for four grassland species,i.e.Medicago sativa,Sorghum bicolor,Leymus chinensis,and Caragana microphylia,were conducted under three nitrogen levels,which were the control(CK) with no nitrogen addition,the medium(N1) with 30gN/m2 addition,and the high(N2) with 60gN/m2 addition,at Taipusiqi Grassland-Cropland Ecosystems Experiment Station of Inner Mongolia.Medicago sativa is a perennial legumes grassland species,Caragana microphylia is a legumes shrub,Leymus chinensis is a perennial C3 plant,and Sorghum bicolor is an annual C4 species.The results show that the above-ground biomass of all the four species increased significantly after nitrogen addition,with the largest above-ground biomass occurred under N1 level for Medicago sativa(with 24.8% higher than CK),but under N2 level for the other three species(with 45.6,39.3,and 72.2% higher than CK for Sorghum bicolor,Leymus chinensis,and Caragana microphylia,respectively).The stem biomass of Sorghum bicolor,Leymus chinensis,and Caragana microphylia was also increased significantly under increasing nitrogen level.The leaf biomass reached the largest under N1 level for Medicago sativa and Caragana microphylia(98.47g/m2 and 143.87g/m2),but under N2 level for Sorghum bicolor and Leymus chinensis(69.20g/m2 and 95.07g/m2).In contrast,the underground biomass of all the four species was the largest under N1 level.The biomass of coarse roots(with diameter >2mm) of Medicago sativa,Sorghum bicolor,and Caragana microphylia didn′t increase significantly,while the rhizome biomass of Leymus chinensis increased significantly.However,the biomass of fine roots(with diameter ≤2mm) of all the four species decreased greatly with higher nitrogen level.Overall,the aboveground biomass and fine root biomass of the four species were sensitive to nitrogen addition.The root/shoot ratio of all the four species declined after nitrogen addition,with the lowest ratio under N1 level for Medicago sativa(1.62),and under N2 level for Sorghum bicolor,Leymus chinensis,and Caragana microphylia(0.57,1.02,and 0.41 respectively).The stem/leaf ratio of Medicago sativa and Leymus chinensis decreased with increasing nitrogen addition,while that of Sorghum bicolor and Caragana microphylia increased.In summary,the four species,even the two legumes had different response to nitrogen addition,i.e.,higher nitrogen addition could increase the biomass of gramineous species significantly and change their biomass allocation pattern obviously,while the aboveground and underground biomass of Medicago sativa didn′t increased significantly,and the biomass allocation pattern didn′t change.The rhizome and leaf biomass of Leymus chinensis increased greatly with nitrogen addition,while Sorghum bicolor and Caragana microphylia allocated more biomass to stem.更多还原