氮素和植物生长促进剂对羊草生长及竞争力的影响

选取羊草、斜茎黄芪、克氏针茅3种内蒙古典型草原常见植物,通过不同植物物种组合(单独种植或者羊草与其他两种混合种植)、施加不同剂量的氮素(0、0.1、0.2、0.4、0.8mg·g^-1)和植物生长促进剂——油菜素内酯(0.005 mg·g^-1)的温室盆栽试验,分析氮素和油菜素内酯对羊草生长及其与其他植物竞争力关系的影响.结果表明:添加氮素对羊草、斜茎黄芪的生物量影响显著,对克氏针茅的生物量影响较弱,并且氮素的影响因其伴生植物的不同而改变.氮素添加显著增加了羊草在单独种植和与斜茎黄芪混合种植时的地上生物量,但显著降低了与克氏针茅混合种植时的地下生物量.由于土壤可利用氮增加,羊草的地上与地下分配发生变化,表现为单独种植、与克氏针茅混合种植时,根冠比下降;与斜茎黄芪混合种植时,氮素添加对羊草根冠比的影响则不显著.油菜素内酯对植物生长的显著影响不普遍,仅显著降低了斜茎黄芪单独种植时的地下生物量;在羊草与斜茎黄芪混合种植时,显著增加了羊草地上生物量.油菜素内酯和氮适量联用可有效增加特定物种组合的生物量,从而在退化草地恢复中具有一定的应用前景.

Effects of nitrogen and plant growth promoter addition on the growth and competitiveness of Leymus chinensis

With a greenhouse pot experiment, we investigated the effects of nitrogen (N) and plant growth promoter (brassinolide, BR) addition on the growth and competitive ability of three common plant species of typical steppe in Inner Mongolia, including Leymus chinensis, Astragalus adsurgens and Stipa krylovii. We added N at rates of 0, 0.1, 0.2, 0.4, 0.8 mg·g^-1 soil and BR at rates of 0 and 0.005 mg·g^-1 soil during plant growth in monoculture or with L. chinensis being planted in mixing with other two species, respectively. There were significant effects on biomass of L. chinensis and A. adsurgens, but not on that of S. krylovii with increase of N and BR addition. The effects of N addition on the growth of L. chinensis varied with accompanying plant species. Nitrogen addition increased aboveground biomass production of L. chinensis when growing in monoculture and mixed with A. adsurgens, but decreased its belowground biomass when growing mixed with S. krylovii. With increasing soil N availability, plant biomass allocation of L. chinensis showed significant decrease in root-shoot ratio when it was in monoculture or mixed with S. krylovii, but similar changes were not found when it was planted in mixing with A. adsurgens. The significant effects of BR addition on plant growth appeared occasionally. BR addition significantly reduced belowground biomass of A. adsurgens in its monoculture and significantly increased aboveground biomass of L. chinensis when it was planted in mixing with A. adsurgens. The results indicated that the appropria-tely combined addition of N and BR could effectively enhance biomass production of specific species combinations in grasslands, which has application prospects in the restoration of degraded grassland.