Intercropping Acacia mangium stimulates AMF colonization and soil phosphatase activity in Eucalyptus grandis

<div><p>ABSTRACT: Arbuscular mycorrhizal fungi (AMF) are very important to plant nutrition, mostly in terms of acquisition of P and micronutrients. While Acacia mangium is closely associated with AMF throughout the whole cycle, Eucalyptus grandis presents this symbiosis primarily at the seedling stage. The aim of this study was to evaluate the dynamics of AMF in these two tree species in both pure and mixed plantations during the first 20 months after planting. We evaluated the abundance, richness and diversity of AMF spores, the rate of AMF mycorrhizal root colonization, enzymatic activity and soil and litter C, N and P. There was an increase in AMF root colonization of E. grandis when intercropped with A. mangium as well as an increase in the activity of acid and alkaline phosphatase in the presence of leguminous trees. AMF colonization and phosphatase activities were both involved in improvements in P cycling and P nutrition in soil. In addition, P cycling was favored in the intercropped plantation, which showed negative correlation with litter C/N and C/P ratios and positive correlation with soil acid phosphatase activity and soil N and P concentrations. Intercropping A. mangium and E. grandis maximized AMF root colonization of E. grandis and phosphatase activity in the soil, both of which accelerate P cycling and forest performance.</p></div

Principal coordinate analysis (PCoA) based on an OTUs matrix obtained in sequencing 16S (rRNA) through the Ion torrent platform.

<p>Groups based on the Bray-Curtis algorithm. 100A: <i>A</i>. <i>mangium</i> in a monospecific plantation system; A(A+E): mixed plantation of <i>A</i>. <i>mangium</i> and <i>E</i>. <i>grandis</i> with sampling at the <i>Acacia</i> base; 100E: <i>E</i>. <i>grandis</i> in a monospecific system; and E(A+E): mixed plantation of <i>A</i>. <i>mangium</i> and <i>E</i>. <i>grandis</i> with sampling at the <i>Eucalyptus</i> tree base. (A) refers to a total PCoA including all soil layers (0 to 800 cm) and all treatments; (B) refers to a soil layer depth between 0 and 100 cm, whereas (C) evaluates between 100 and 300 cm, (D) between 300 and 500 cm, (E) between500 and 700 cm and (F) from700 to 800 cm.</p

Abundance (n = 3) of the 16S rRNA gene.

<p>Treatments: 100A (<i>A</i>. <i>mangium</i> in a monospecific plantation system); A(A+E) (mixed plantation of <i>A</i>. <i>mangium</i> and <i>E</i>. <i>grandis</i>, with sampling at the <i>Acacia</i> base); 100E (<i>E</i>. <i>grandis</i> in a monospecific plantation system); and E(A+E) (plantation of <i>A</i>. <i>mangium</i> and <i>E</i>. <i>grandis</i>, with sampling at the <i>Eucalyptus</i> base). Asterisks indicate significant differences (p<0.05) between treatments.</p

Maximum contribution based on the SIMPER test of the bacterial phyla and classes.

<p>Results point to a significant separation of treatment 100E (Eucalypt monoculture) from the other cultivation systems.</p