Interactive effects of nitrogen and silicon addition on growth of five common plant species and structure of plant community in alpine meadow

Great efforts have been made on the assessment of the effects of nitrogen (N) fertilization or silicon (Si) addition on plant growth and community composition. However, their interactive effects were not well documented. We here tested the effects of N addition (0, 70, 140 and 210 kg ha−1 of N) on the leaf N content, growth, photosynthetic characteristics of five common species and structure of community (biomass, height, abundance and species richness) with or without Si (14.36 kg ha−1) incorporation. Different species and whole community responded different. As compared to without Si, Si incorporation increased the net photosynthetic rate (Pn) and biomass of species Elymus nutans by 16.7 and 31.1%, Kobresia capillifolia by 10.4 and 11.1%, Oxytropis kansuensis by 42 and 18.0%, Anemone rivularis by 14.3 and 157%, Potentilla fragarioides by 12.5 and 91.7%, plant abundance and species richness of community by 6.2 and 11.8% under N addition of 210 kg ha−1. The effect of Si supply on species richness was more efficient under low N addition than high N addition. Together, our results indicate that N fertilization incorporation with Si addition benefits plant growth for higher-photosynthetic activity of individual species and higher-species richness of community in alpine meadow.