[Comparison of root traits of Stipa krylovii and Allium polyrhizum under grazing in typical steppe.]

Plant ecological adaptation is associated with root traits. To clarify the differences of root traits between two dominant species, Stipa krylovii and Allium polyrhizum, under different grazing intensities (light, moderate, and heavy grazing intensities), we measured root traits, including root length, root surface area, root diameter, root volume, root tips, root bifurcations, specific root length, and specific surface area. We analyzed the root morphological patterns of tip proportion, length proportion, surface proportion and volume proportion of both species, and examined their ecological adaptation strategies under grazing. The results showed that grazing inhibited aboveground and belowground growth of S. krylovii, but promoted belowground growth of A. polyrhizum. In addition, the effects of grazing on belowground part of S. krylovii was greater than aboveground part. These results indicated that the growth of S. krylovii was maintained by the aboveground part and that of A. polyrhizum was maintained by the belowground part under grazing. Root length, root bifurcations, root surface area and root tips were the main factors affecting root traits of S. krylovii, while root length, root surface area and root volume were the main factors affecting root traits of A. polyrhizum. S. krylovii could adapt to grazing stress by increasing length proportion, surface proportion and volume proportion of diameter class of 0-0.7 mm, while A. polyrhizum by increasing the length proportion, surface proportion and volume proportion of diameter class of 1.4-1.8 mm. The study on the differences of root traits between S. krylovii and A. polyrhizum could help provide a scientific basis for controlling grassland degradation.植物根系属性与其生态适应性密切相关。为明确不同放牧干扰下克氏针茅和多根葱两种优势植物根系属性差异,比较了轻度放牧、中度放牧、重度放牧下克氏针茅和多根葱地下根系长度、根系表面积、根系直径、根系体积、根尖数、根系分叉数、比根长和比表面积的形态特征,分析了2种植物根尖比、根长比、表面积比、体积比等根系形态格局,研究两种植物对放牧压力的生态适应性。结果表明: 放牧抑制了克氏针茅地上和地下部分生长,促进了多根葱地下部分生长,且放牧对克氏针茅地下部分的影响大于地上部分,表明在放牧干扰下克氏针茅通过地上部分来维持生长,多根葱通过地下部分来维持生长;根系长度、根系分叉数、根系表面积和根尖数是影响克氏针茅根系属性的主要因子,根系长度、根系表面积和根系体积是影响多根葱根系属性的主要因子;克氏针茅通过增加0～0.7 mm径级根长比、表面积比和体积比来适应放牧压力,而多根葱通过增加1.4～1.8 mm径级根长比、表面积比和体积比来适应放牧环境。研究克氏针茅和多根葱根系属性差异可以为草地退化防治提供科学依据。.