土壤水分及其垂直分布对内蒙古草原冰草和冷蒿竞争的影响

Effects of soil water and its vertical distribution on competition between Agropyron cristatum and Artemisia frigida in the Inner Mongolia grassland

内蒙古退化冷蒿草原围封恢复演替3—4年,植物群落更替出现半灌木冷蒿(Artemisia frigida)向禾草冰草(Agropyron cristatum)群落突然转变的现象,这对内蒙古草原植被恢复具有积极的作用,但目前关于冰草-冷蒿演替和竞争机制的研究鲜见报道。水分作为草原植被生长的主要限制因子,是影响群落演替的重要因素。气候干旱和过度放牧导致草原土壤水分垂直分布发生明显变化。由于冰草和冷蒿的根系分布深浅不同,土壤水分垂直变化可能会影响冰草-冷蒿的竞争。为探讨土壤水分及其垂直分布对冰草和冷蒿竞争的影响,本盆栽试验设置冰草、冷蒿单种以及混种处理,并进行不同土壤深度(0—30cm,30—60cm)的水分处理(上干下湿、上湿下干、上干下干),结果表明:(1)与冷蒿相比,冰草受土壤水分变化影响显著,相对于上干下干处理,冰草在湿润(上干下湿或者上湿下干)处理的地上、地下生物量均显著增加,而冷蒿没有显著变化;(2)上干下湿和上湿下干处理间,冰草、冷蒿的地上、地下总生物量和根长差异均不显著;(3)不同水分处理,冰草和冷蒿的根系均可分布在30—60cm土壤中,且土壤30—60cm层冰草单种的根生物量和根长显著高于冷蒿单种;(4)相对竞争强度和竞争攻击力系数表明:湿润处理冰草的竞争力大于冷蒿;上干下干处理冷蒿的竞争力大于冰草。土壤水分变化引起冰草、冷蒿的明显竞争,上湿下干与上干下湿处理间冰草与冷蒿竞争力差异不显著。由于冰草和冷蒿均为多年生物种,冰草-冷蒿的竞争实验仍需在今后的研究中反复地验证。

When the degraded Artemisia frigida(A.f)grassland was enclosed and recovered for 3—4 years,the plant community replacement showed a sudden transformation from semi-shrub A.f to Agropyron cristatum(A.c)community in the Inner Mongolia grassland.It has a great positive effect on the vegetation restoration from the A.f community to the A.c community in the Inner Mongolia grassland.However,few researches were reported on the succession and competition mechanisms of the A.c-A.f community.Water is a primary factor affecting plant growth and community succession.Climatic drought and overgrazing have led to changes in the vertical distribution of soil moisture in grassland.Due to the different depths of root distribution of A.c and A.f,the different vertical distributions of soil moisture may affect the competition between A.c and A.f.To explore the effect of soil water and its vertical distribution on the A.c and A.f competition,a pot experiment was set up,with three planting methods(A.c monoculture,A.f monoculture,intercropping of A.c and A.f)and three water treatments in upper(0—30 cm)and lower soil(30—60 cm)layers,including drought in upper and wet in lower soil(drought-wet),wet in upper soil and drought in lower soil(wet-drought),and drought both in upper and lower soil layers(drought-drought).The results showed that:(1)Compared with A.f,A.c was significantly affected by the change of the soil water content.Compared with the drought-drought treatment,the aboveground biomass and belowground biomass of A.c increased significantly in the wet(wet-drought or drought-wet)treatment.In contrast,the aboveground and belowground biomass of A.f did not change significantly in wet treatment.(2)There was no significant difference in aboveground and belowground biomass and root length of A.f and A.c between drought-wet and wet-drought treatment.(3)The roots of A.c and A.f could be distributed in a 30—60 cm soil layer under different water treatments.The root biomass and root length of A.c were significantly higher than those of A.f in the 30—60 cm soil layer.(4)The relative competition intensity and competitive attack coefficient showed that the competitiveness of A.c was greater than that of A.f under wet treatment,while the competitiveness of A.f was greater than that of A.c under drought-drought treatment.The changes in soil moisture caused obvious competition between A.c and A.f,but the competitiveness between A.c and A.f was similar in the wet-drought and drought-wet treatments.Due to both A.c and A.f being perennial species,the competition experiment of A.cA.f still needs to be verified repeatedly in the future.