The role of soil chemistry and plant neighbourhoods in structuring fungal communities in three Panamanian rainforests

Abstract

1. Fungi play critical roles in ecosystem processes and interact with plant communities in mutualistic, pathogenic, and commensal ways. Fungal communities are thought to depend on both associated tree communities and soil properties. However, the relative importance of the biotic and abiotic drivers of soil fungal community structure and diversity in lowland tropical forests remains poorly understood. 2. We examined the community structure of trees and fungi at different levels of phosphorus (0Á17-16Á3 mg kg À1 ) in moist tropical forests in Panama. We predicted that arbuscular mycorrhizal (AM) fungal composition would be more strongly associated with soil properties than with local tree communities while the composition of other fungal clades would be more strongly correlated with local tree communities than soil properties. We also predicted that fungal operational taxonomic unit (OTU) richness would be negatively correlated with soil fertility and positively correlated with tree species diversity within and among forests. 3. We characterized soil chemistry, fine root biomass, and sequenced the ITS1 barcode region to describe fungal community composition from 70 soil cores across three 1-ha tropical rainforest sites in Panama. The sites vary in soil chemistry, including P, and in tree species community composition, but experience similar annual rainfall. 4. AM fungal community composition was partially correlated with soil chemistry (r = 0Á32, P ≤ 0Á001), but not with local tree communities, while non-AM fungal communities were nearly equally correlated with soil chemistry (Partial Mantel test, r = 0Á38, P ≤ 0Á001) as with tree communities (r = 0Á36, P ≤ 0Á001). Linear models showed that AM OTU richness was not explained by any independent variable. For non-AM fungi, phosphorus, pH, and soil moisture better predicted OTU richness across all cores than other biotic and abiotic factors. 5. Synthesis. Our results show that AM fungal structure is driven primarily by soil chemistry. For non-AM fungi, soil properties and the local tree community can play a joint role in structuring communities. Furthermore, we found that more diverse local tree communities did not harbour more fungal species. Our results suggest that soil properties act as an environmental filter for both trees and fungi, setting the stage for interactions between the two.

Nutrient limitation of soil microbial processes in tropical forests

“…, Schappe et al. ). Few studies specifically analyzed shifts in fungal, bacterial, and mycorrhizal community composition in response to nutrient additions (Kaspari et al.…”

“…Thus, changes in microbial community composition within functional guilds (Kaspari et al 2010, Camenzind et al 2014), but also among them (Liu et al 2013, Fanin et al 2016) will feed back on responses to nutrient additions (Leff et al 2012). Very broad parameters like soil microbial biomass or respiration are useful for assessing the response of the whole microbial community, whereas analyses of specific functional or taxonomic groups reveal essential information on group-specific demands, which remain poorly understood in tropical forests (Kaspari et al 2010, Schappe et al 2017. Few studies specifically analyzed shifts in fungal, bacterial, and mycorrhizal community composition in response to nutrient additions (Kaspari et al 2010, Camenzind et al 2014).…”

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

“…Several studies have shown the effects of soil nutrients, pH and moisture on both the amount of root colonisation and mycorrhizal community composition (Krüger et al 2015;Schappe et al 2017). Neighbouring plants in a community can also have strong effects on root colonisation by mycorrhizal fungi (Dickie et al 2004;Kennedy et al 2012;Teste et al 2014).…”

The role of plant mycorrhizal type and status in modulating the relationship between plant and arbuscular mycorrhizal fungal communities

“…Environmental conditions affect both plant and AM fungal communities directly and indirectly (Davison et al, 2015;Schappe et al, 2017). The relatedness of plant and AM fungal communities could therefore be a result of plant-fungal interactions (the driver-/passenger hypothesis; Hart et al, 2001) or simply covariation of both communities with environmental conditions (the habitat hypothesis; .…”