Seasonality regulates the structure and biogeochemical impact of ectomycorrhizal fungal communities across environmentally divergent neotropical dry forests

Abstract

Ectomycorrhizal (ECM) symbioses support forest functioning globally, yet both the structure and function of ECM fungal communities in seasonally dry neotropical forests (SDTFs), known for extreme heterogeneity in vegetation and edaphic properties, remain under characterized. Here, we evaluated the relative influences of seasonal versus spatial variation in ECM fungal community structure in soils from four environmentally divergent SDTFs. We also assessed the importance of biotic and abiotic drivers of SDTF ECM fungal community structure at regional scales, as well as ECM impacts on soil carbon (C) and nitrogen (N) cycling. ECM fungal frequency, relative abundance and richness all increased in the wet season, but spatial rather than seasonal effects explained more variation in community composition. Across the four SDTFs investigated, differences in tree communities drove ECM fungal community turnover more than geographic distances, site abiotic conditions or soil chemistry. Although soil moisture and ECM tree basal area were stronger predictors of soil biogeochemistry, incorporating ECM fungal community composition and relative abundance added explanatory power to models of soil C and N cycling in the wet season. Synthesis: Our results highlight the importance of seasonality and plant community composition in shaping different aspects of SDTF ECM fungal community structure and diversity as well as the potential for both the plant and fungal components of ECM symbioses to impact soil functioning across heterogenous SDTFs. Furthermore, our findings suggest that alterations in SDTF plant community composition due to climate or land‐use change will have important consequences for ECM fungal diversity and associated effects on soil biogeochemical cycling.

Soil mycobiomes in native European aspen forests and hybrid aspen plantations have a similar fungal richness but different compositions, mainly driven by edaphic and floristic factors

“…A study in Austria found no Populus tremula- associated EcM taxa that were significantly associated with summer or autumn conditions ( Krpata et al, 2008 ). Yet many studies have found significance of seasonal factors on fungal relative abundance ( Zhao et al, 2023 ) and community compositions ( Vargas-Gastélum et al, 2015 ; Beidler et al, 2023 ). Others have suggested that host-tree characteristics have more impact than the seasonal factor alone in describing changes in fungal communities ( Park et al, 2020 ), thus the seasonal factor should be considered in interaction with tree or site characteristics.…”

Seasonality and longer-term development generate temporal dynamics in the Populus microbiome

“…4 and 6 ). The relative abundance of ectomycorrhizal fungi typically increases during seasons with high photosynthetic activity ( 20 , 35 , 81 ), likely explaining why relative abundance of these fungi was greatest during summer ( Fig. 6 ).…”

“…This evidence presents the possibility that tree microbiomes change continuously over time, causing seasonal fluctuations and longer-term shifts to occur simultaneously. However, studies of intra-annual variation in the composition of tree microbiomes typically span a single year ( 20 , 35 – 37 ). Consequently, it has remained challenging to disentangle seasonal variation from longer-term shifts in tree-associated microbial communities, as well as from numerous climatic, edaphic, and host genotypic differences that correlate with spatial variation in the composition of plant microbiomes ( 37 – 42 ).…”