The Response Of Leymus Chinensispopulation Root System To Water And Nitrogen Gradient In Degraded Grassland

Typical steppe is one of the important grassland types in North China, resaerch on the response of root characteristics of Leymus chinensis to water gradients has an important scientific significance for revealing root growth and development of steppe plants and theirs ecological stability. A lightly and a heavily degraded grassland communities were selected in Xilinguole typical steppe region of Inner Mongolia. A water gradient experiment was designed to research the response of root system characteristics of Leymus chinensis population to water gradient and nitrogen gradient in different degraded degree grassland.The main results as follows:(1) With the decrease of water yield, the aboveground height of Leymus chinensis gradually decreased while main root length and root volume increased gradually in both types of grasslands, the root surface area had a increasing trend, but only significant correlated to water yield in heavily degraded grassland, root diameter had a decreasing trend, but only significant correlated to water yield in lightly degraded grassland. Comparing different degradation degree of grasslands, Most of root characters of Leymus chinensis have no significant difference on most water gradient, except that, under moist condition (600mm), the root surface area and root volume in lightly degraded grassland was much higher than that in heavily degraded grassland. Under drought condition (150mm), the main root length in heavily degraded grassland was much higher than that in lightly degraded grassland. (2) Add a low concentration of nitrogen (30g/m2), the root surface area and root volum and the main root length is gradually increased in heavily degraded grassland of Leymus chinensis,the aboveground height of leymus chinensis increasing trend in lightly degraded grasslands; In moderate concentration nitrogen add (50g/m2), leymus chinensis underground roots is miniaturization trend in heavily degraded grassland. Lightly degraded grasslandground aboveground height of Leymus chinens and underground root system was the trend of the growth and elongation;Add a high concentration of nitrogen (80g/m2), the main root length is gradually increased,the root volume and root area did not change significantly, fibrous root system is reduced, the aboveground height of Leymus chinens is gradually growth in heavily degraded grassland of Leymus chinensis. The lightly degraded the Leymus chinensis ground height increasing trend, root morphology characteristics did not change significantly. Correlation shows that only the heavily degraded grassland of Leymus chinens root area, volume was negatively correlated with the concentration of nitrogen, the aboveground height of Leymus chinens was a positive correlation with the concentration of nitrogen. The different degradation grasslands compare, Leymus chinensis root characteristics were no significant differences in add most of the nitrogen gradient, except that, the root surface area and root volume in heavily degraded grassland were much higher than those in lightly degraded grassland.Under high condition, the aboveground height of Leymus chinens the in heavily degraded grassland were much higher than those in lightly degraded grassland...