Stoichiometric homeostasis in response to arbuscular mycorrhiza fungi supply in Morus in rocky desertification areas
Ecological stoichiometry is a pertinent theory to reveal the adaptability of mulberry-inoculated arbuscular mycorrhizal fungi to rocky desertification areas.Two sets of experiments were performed,one in which Funneliformis mosseae(Fm)and Rhizophagus intraradices(Ri)were inoculated and the other in which uninoculated plants were used as controls.After four months,soil and mulberry organs were sampled.Total carbon(C)and total nitrogen(N)were measured and the ecological stoichiometric ratio and stoichiometric homeostasis indices were calculated.With increasing soil depth,soil total organic C(TOC)content and the C∶N ratio decreased,but the total N(TN)content increased.The inoculation of Fm and Ri significantly(P＜0.05)increased TOC content from 0.93％to 5.00％and C∶N ratio from 1.81％to 16.20％(both P＜0.05),and reduced TN content from 1.49％to 9.48％.C content and C∶N ratio in mulberry leaves were lower than those in roots and stems,but the N content in the mulberry leaves was higher than that in the roots and stems.Inoculation with arbuscular mycorrhizal fungi significantly(P＜0.05)increased the C content from 1.30％to 3.64％,and C∶N ratio from 1.78％to 14.51％in mulberry leaves.The stoichiometric homeostasis indices were different for N and C∶N in mulberry organs.The second experiment did not involve inoculation.The N and C∶N homeostasis indices of mulberry stems and roots were lower than those in the inoculated experiment,indicating instability.Inoculation with Fm enhanced the homeostasis indices of N in mulberry roots(H=2.94)but reduced the indices of C∶N in leaves(H=2.32).Inoculation with Ri enhanced the homeostasis index of N in the stems(H=1.69).Inoculation of arbuscular mycorrhiza fungi increased TOC content of different soil profiles,reduced TN content in rocky desertification soil,and regulated C∶N changes.These findings support the"slow decomposition"hypothesis.Arbuscular mycorrhiza fungi promoted the uptake and transfer of N in mulberry roots.However,N and C∶N stabilities of mulberry organs are regulated by the species of arbuscular mycorrhizal fungi.
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