Host identity and neighborhood trees affect belowground microbial communities in a tropical rainforest

Variations of arbuscular mycorrhizal fungi following succession stages in a tropical lowland rainforest ecosystem of South China

Introduction

The grasslands in the Nature Reserve of Ganshenling, in the south of Hainan Island, were first formed after deforestation disturbance before a natural restoration of shrubs and secondary forests. However, the stages of grassland and shrubs in some parts of Ganshenling regions could not be naturally restored to secondary forests. In addition, the forest form of the secondary forest after 40 years (40a) of succession was similar to that of the secondary forest of 60 years (60a). However, it was not known whether the microorganisms recovered to the level of the secondary forest of 60a. Arbuscular mycorrhizal fungi (AMF) are plant root symbionts that can improve the nitrogen and phosphorus absorption of plants and play a key role in secondary forest succession. An understanding of the essential role of soil AMF in secondary forest succession of tropical rainforest in Ganshenling regions is still limited.

Methods

Therefore, the soil of 0–10 cm was collected with the help of a 5-point sampling method in grassland, shrubs, and second tropical lowland rainforest of 40a and 60a. We studied community changes in AMF with the succession and explored the impacts of soil physicochemical properties on soil AMF.

Results

Our findings were as follows: (1) Different successional stages showed divergent effects on soil AMF communities. (2) After 40a recovery, the alpha-diversity indices of AMF recovered to the level of secondary forest of 60a, but the similarity of soil AMF communities only recovered to 25.3%. (3) Species richness of common species, rare species, and all the species of AMF showed a significantly positive correlation with soil nitrogen. (4) OTU10; OTU6, OTU9, and OTU141; OTU3 and OTU38; and OTU2, OTU15, OTU23, and OTU197 were significantly unique AMF for grasslands, shrubs, and secondary forests of 40a and 60a, respectively. (5) The phylogenetic tree and the heatmap of AMF showed that the OTUs in grasslands and shrubs were in contrast to the OTUs in secondary forests of 40a and 60a.

Discussion

We concluded that the succession of a secondary forest after deforestation disturbance was probably limited by its AMF community.

Hidden Tenants: Microbiota of the Rhizosphere and Phyllosphere of Cordia dodecandra Trees in Mayan Forests and Homegardens

During domestication, the selection of cultivated plants often reduces microbiota diversity compared with their wild ancestors. Microbiota in compartments such as the phyllosphere or rhizosphere can promote fruit tree health, growth, and development. Cordia dodecandra is a deciduous tree used by Maya people for its fruit and wood, growing, to date, in remnant forest fragments and homegardens (traditional agroforestry systems) in Yucatán. In this work, we evaluated the microbiota's alpha and beta diversity per compartment (phyllosphere and rhizosphere) and per population (forest and homegarden) in the Northeast and Southwest Yucatán regions. Eight composite DNA samples (per compartment/population/region combination) were amplified for 16S-RNA (bacteria) and ITS1-2 (fungi) and sequenced by Illumina MiSeq. Bioinformatic analyses were performed with QIIME and phyloseq. For bacteria and fungi, from 107,947 and 128,786 assembled sequences, 618 and 1092 operating taxonomic units (OTUs) were assigned, respectively. The alpha diversity of bacteria and fungi was highly variable among samples and was similar among compartments and populations. A significant species turnover among populations and regions was observed in the rhizosphere. The core microbiota from the phyllosphere was similar among populations and regions. Forests and homegarden populations are reservoirs of the C. dodecandra phyllosphere core microbiome and significant rhizosphere biodiversity.