5 CONCLUSIONS
Seed production of the dominant species in the temperate steppe was
enhanced by N addition, but a high level of N addition stimulated seed
production more than a low N addition. Whereas seed production was
unchanged by P addition alone, it was increased when the latter was in
the presence of N addition. Seed production was enhanced mainly through
an increasing of tiller and inflorescence numbers under N addition, and
by decreased plant density stimulating plant height growth and enabling
seed number per inflorescence under P addition. Our results indicate
that N availability is the main factor limiting seed production, but
seed production can become limited by P availability as N enrichment
increases in the temperate steppe. These timely findings can facilitate
better understanding of grassland seed banks and plant community
structure responses to simultaneous multiple nutrient enrichment under
future nutrient enrichment scenarios.