Metabarcoding analysis of the soil fungal community to aid the conservation of underexplored church forests in Ethiopia

Abstract

Most of the Dry Afromontane forests in the northern part of Ethiopia are located around church territories and, hence, are called church forests. These forests are biodiversity islands and provide key ecosystem services to local communities. A previous study of church forest fungal species was based on sporocarp collections. However, to obtain a complete picture of the fungal community, the total fungal community present in the soil needs to be analyzed. This information is important to integrate church forests into global biodiversity conservation strategies and to understand what actions are required to conserve church forests and their biological components, including fungi, which are known for their exceptionally high diversity levels. We assessed soil fungal communities in three church forests using ITS2 rDNA metabarcoding. In total, 5152 fungal operational taxonomic units representing 16 fungal phyla were identified. Saprotrophs followed by ectomycorrhizal fungi and animal pathogens dominated fungal communities. Significant differences in diversity and richness were observed between forests. Non-metric multidimensional scaling confirmed that fungal community composition differed in each forest. The composition was influenced by climatic, edaphic, vegetation, and spatial variables. Linear relationships were found between tree basal area and the abundance of total fungi and trophic groups. Forest management strategies that consider cover, tree density, enrichment plantations of indigenous host tree species, and environmental factors would offer suitable habitats for fungal diversity, production, and function in these forest systems. The application of the baseline information obtained in this study could assist other countries with similar forest conservation issues due to deforestation and forest fragmentation.

Figure 1

Relative proportions of fungal operational taxonomic units (OTUs) according to their guild assignment at the genus level (trophic groups; the number of OTU; percentage).

Figure 2

The relative richness of the fungal operational taxonomic units (OTUs) of main fungal trophic groups among the three studied Dry Afromontane church forests. Values with the same letter in a group are not significantly different. Bars denote the standard error.

Figure 3

Patterns of fungal species were recorded in three Dry Afromontane forests in Northern Ethiopia. (a) Observed species accumulation curves across the fragmented forests using the rarefaction sample-based estimator of EstimateS. Data were extrapolated following procedures proposed in the EstimateS manual, the points to the right of the red vertical line are the curve that is extrapolated, (b) Rényi diversity profiles of log-transformed fungal OTU abundance data. The profile values for alpha = 0, 1, 2, and infinity indicate the species richness, Shannon diversity index, the logarithm of the reciprocal Simpson diversity index, and Berger Parker diversity index, respectively. If the profile for one sample was consistently higher than the profile for another sample, the sample with the higher-profile was considered more diverse. When curves for two communities intersect, this means that they cannot be ranked. Lines represent the species richness or diversity of the forests. The black lines are the 95% confidence intervals of each curve.

Figure 4

Non-metric multidimensional scaling (NMDS) ordination graph with fitted environmental variables based on dissimilarities calculated using the Bray–Curtis index of fungal community compositions of the three Dry Afromontane church forests in Northern Ethiopia with vascular tree richness displayed as isolines. Arrows represent environmental variables that were most significantly (p ≤ 0.005) related to ordination. Ellipses indicate forest groups. The explanatory variables are shown in blue. RF, annual rainfall; Tmax, average daily maximum temperature for 2019; BA, tree basal area; RF30d, cumulative rainfall 30 days before sampling; Elev, elevation a.s.l.; Lati, latitude; Long, longitude.

Figure 5

Map of the Amhara region in Northern Ethiopia showing the location of the three church forests in which the study plots were located.