Arbuscular mycorrhizal fungi and its influencing factors across five mangrove ecosystems in southern China
Recent studies show that AMF also exist in wetlands, forming symbiotic relationships with many hydrophytic plants. Due to their special habitats and unique distribution pattern, mangrove ecosystems are quite different from other wetlands. In mangroves, AMF symbionts are also common. Many mangrove species, such as Acanthus ilicifolius, Acrostichum aureum, Aegiceras corniculatum, Sesuvium portulacastrum, Borassus flabellifer etc., form symbionts with AM fungi. But little has been known about the distribution of AMF and culturable microorganisms in mangrove ecosystems until now. Our aims of this study were to measure the AMF colonization rate and microbial community richness on a large scale across mangrove forests in southern China and identify the influencing factors, so we conducted field study across five mangrove ecosystems in southern China. Aegiceras corniculatum and Acanthus ilicifolius, both of which were commonly distributed throughout the five selected study sites, were chosen and studied. We took both soil and plant root samples in order to determine AMF and soil microorganisms, soil physicochemical properties were measured to analyze their influences on AMF in mangroves.
Our results showed that AMF were very common in the investigated mangrove ecosystems, with hyphae as the dominant structures in both species. Total AMF colonization rates ranged from 0.33% to 36.50%, which were much lower than in most terrestrial plants. The average spore density in soil samples for Aeg. corniculatum was 49.0 spores per 25g air dried soil, and 51.7 for Aca. ilicifolius. Data analysis revealed that soil P content (p < 0.05) and seawater salinity (p < 0.05) may be important factors influencing AMF in mangroves. As soil P content was very low in this study, it may be the limiting factor for AMF colonization, while abundant soil N content did not seem to affect AMF colonization rates and spore density. Our results also indicated that seawater salinity may be an important abiotic factor influencing AMF in mangrove ecosystems, while the interaction between AMF and soil microbial numbers was not significant. When analyzing AMF colonization rate and spore density data, it seems that AMF colonization rate for both plant species distributed a trend to first increase and then decrease from north to south, spore density for Aca. ilicifolius also shows the trend. And we think this might be an interesting topic for studying AMF in mangroves, when considering the distribution of mangrove plants under different latitudes.