Experimental duration determines the effect of arbuscular mycorrhizal fungi on plant biomass in pot experiments: A meta-analysis

Abstract

Arbuscular mycorrhizal fungi (AMF) play various important roles in promoting plant growth. Numerous environmental and evolutionary factors influence the response of plants to AMF. However, the importance of the individual factors on the effects of AMF on plant biomass is not clearly understood. In this study, a meta-analysis using 1,640 observations from 639 published articles related to the influence of AMF on the plant shoot, root, and total biomass was performed; 13 different experimental setting factors that had an impact on the influence of AMF and their importance were quantitatively synthesized. The meta-analysis showed that AMF had positive effects on the plant shoot, root, and total biomass; moreover, the experimental duration, plant root-to-shoot ratio (R/S), AMF root length colonization, plant family, pot size, soil texture, and the soil pH all influenced the effects of AMF on the shoot, root, and total biomass. In addition, the plant root system and plant functional type had impacts on the effect of AMF on shoot biomass; AMF guild also impacted the effect of AMF on root biomass. Of these factors, the experimental duration, plant R/S, and pot size were the three most important predicting the effects of AMF on the plant shoot, root, and total biomass. This study comprehensively assessed the importance of the different factors that influenced the response of plants to AMF, highlighting that the experimental duration, plant R/S, and pot size should be taken into consideration in pot experiments in studies of the functions of AMF. Multiple unfavorable factors that may obscure or confound the observed functions of AMF should be excluded.

Keywords: Arbuscular mycorrhizal fungi; effect size; experimental duration; plant biomass; pot size; root/shoot ratio.

Figure 1

Effect of arbuscular mycorrhizal fungi (AMF) inoculation on the plant shoot, root, and total biomass.

Figure 2

Linear relationships between the effect size of arbuscular mycorrhizal fungi (AMF) on plant biomass (shoot, root, and total) and the AMF root length colonization (RLC), plant root-to-shoot ratio (R/S), and experimental duration. The significance test for the linear relationship was based on a random effects model with a residual maximum likelihood (REML) method. P-values ≤0.05 were considered significant. Values in parentheses are the number of observations included in the analysis.

Figure 3

Effect of arbuscular mycorrhizal fungi (AMF) number and guild, plant family, and root system on the effect size of AMF on plant shoot (A), root (B), and total (C) biomass. Values in parentheses are the number of observations included in the analysis. The significance test for between-level differences was based on a random effects model with a residual maximum likelihood (REML) method. P-values ≤0.05 were considered significant. Different capital letters indicate significant differences compared with the other groups as assessed using a random effects model with a REML method.

Figure 4

Effect of plant life history, plant functional type, pot size, soil texture, soil available phosphorus (AP), and soil pH on the effect size of arbuscular mycorrhizal fungi (AMF) on plant shoot (A), root (B), and total (C) biomass. Values in parentheses are the number of observations included in the analysis. The significance test for between-level differences was based on a random effects model with a residual maximum likelihood (REML) method. P-values ≤0.05 were considered significant. Different capital letters indicate significant differences compared with the other groups as assessed using a random effects model with a REML method.

Figure 5

Variable importance of the moderators for the effect of arbuscular mycorrhizal fungi (AMF) on plant shoot (A), root (B), and total (C) biomass. This weighted random forest analysis included the significant moderators in the previous random effects model.