Responses of Plant Growth to N or P Addition Vary With Mycorrhizal Strategy

Mycorrhizal fungi form symbiotic relationships with most terrestrial plants. Soil nutrients affect the mycorrhizal symbiotic formation, further determine plant growth. However, little is known on the role of mycorrhiza in response of host plant growth to nutritional additions in natural ecosystem. A new database was established including the index of plant growth and their mycorrhizal status based on a global database of interactive effects of nitrogen (N) and phosphorus (P) additions on plant growth. We examined effects of mycorrhizal strategy on the responses of plant growth to N or P addition. We found that plant growth was closely related to mycorrhizal strategies. N addition increased 35% aboveground biomass (AGB) of host plants associated with arbuscular mycorrhiza (AM), whereas decreased it by 9% in plants non-associated with AM (nonAM). P addition or NP addition all increased AGB regardless of mycorrhizal type, but the effect of nonAM plants was stronger than that of AM plants. Structural equation modelling (SEM) analysis showed that N addition had an positive effect on leaf N:P ratios through affecting leaf N of AM plants (r = 0.25) and nonAM plants (r = 0.33) whereas P addition had an negative effect on leaf N:P ratios through affecting leaf P of AM plants (r = 0.29) and nonAM plants (r = 0.45). Our results highlighted the biomass production of plants was controlled mainly by P addition and AM increased the accumulation of AGB by promoting plant P uptake. Moreover, AMF have different functions depending on the nutritional conditions, further regulated plant growth.