Study On Ecological Stoichiometric Characteristics Of Carbon And Nitrogen In Legumes And Grasses At Different Growth Stages

Carbon and nitrogen ecological stoichiometry has now been one of the most important topics in agriculture, ecology and global change. The temporal variation in carbon and nitrogen stoichiometry reflects the change in plant growth rate with time. So, related researches will be of great help to understand plant responses to environment. In this study, some widely used forages including lucerne (Medicago sativa cv. Longdong), sainfoin (Onobrychis viciaefolia) and vetch (Vicia sativa) and annual ryegrass (Lolium multiflorum) were used to investigate C, N ecological stoichiometric characteristics in different organs of the legumes and grasses at different growth stage. In addition, the relationship of C, N stoichiometry between forage and soil was analysed.1. Generally, forage C:N ratio was lower at the branching stage and was greater at the blooming stage. The ratio in the field tended to increase with the growth, while it increased firstly and then decreased, finally increased again in the glasshouse pot experiment. Forage organic carbon content increased with the growth, and total nitrogen content was various with the least value measured at the later growth stage.2. The C:N ratio of annual ryegrass was greater than those in other forages tested. The organic carbon content of annual ryegrass was obviously greater than those in the legumes, and the total nitrogen content was lower.3. Forage C:N ratio in leaves during the whole growing period was less than those in stems and roots. Organic carbon content in roots was less than those in leaves and stems. Total nitrogen content in leaves was significantly greater than those in stems and roots.4. Overally, there was no obvious correlation between organic carbon content and C:N ratio, while significant correlations were observed between total nitrogen content and C:N ratio, and organic carbon content. In the field, there were no obvious correlation between organic carbon content and total nitrogen content, and C:N ratio, while significantly negative correlation was observed between total nitrogen content and C:N ratio. In the pot experiment, significant correlations were observed between total nitrogen content and organic carbon content, and C:N ratio. There was no obvious correlation between organic carbon content and C:N ratio.5. There were significantly positive correlations of C:N ratio among forage leaf, stem and root.6. There was no obvious correlation of C:N ratio between forage organs and0-10cm depth of soils. Forage leaf C:N was observed to be very significantly positively correlated to C:N ratio in10-20cm soils. There was significant correlation of stem C:N ratio with the C:N ratio in soils at10-20and20-30cm depths. Between forage root and20-30cm depth of soils, significantly positive correlation was observed.