Stoichiometric characteristics of different agroecosystems under the same climatic conditions in the agropastoral ecotone of northern China

Ecological stoichiometry affects the processes and functions of ecosystems, but the similarities and differences of stoichiometric characteristics among diverse agropastoral ecosystems under the same climatic conditions remain unclear. In this study, plant and soil stoichiometric characteristics of different agroecosystems, namely natural grassland (free-grazing and mowed grassland), artificial grassland (oat, Chinese leymus and corn silage), field crops (naked oats, flax and wheat) and commercial crops (cabbage and potatoes), were investigated in Guyuan County, China. Results showed total nitrogen (TN), total phosphorus (TP) and N : P ratios in plant tissue varied significantly among ecosystem types (P 0.05). However, the C : P ratio was lower in potato than cabbage sites (24.64 vs 33.17), and was lower at both these sites than in other agroecosystems (P 0.05). Above all, N is more likely to be limiting than P for biomass production in local agroecosystems. Soil C : P and N : P ratios decreased significantly with an increase in the utilisation intensity (from natural grassland to commercial crop). The findings of this study suggest that restoring, preserving and increasing soil organic carbon (especially for cabbage and potatoes), scientifically adjusting the application of N and P fertiliser and enhancing subsidies for low-loss soil nutrient systems, such as grassland, rather than commercial crops will help improve and sustain agroecosystems.