Experimental warming increases fungal alpha diversity in an oligotrophic maritime Antarctic soil

Abstract

The climate of maritime Antarctica has altered since the 1950s. However, the effects of increased temperature, precipitation and organic carbon and nitrogen availability on the fungal communities inhabiting the barren and oligotrophic fellfield soils that are widespread across the region are poorly understood. Here, we test how warming with open top chambers (OTCs), irrigation and the organic substrates glucose, glycine and tryptone soy broth (TSB) influence a fungal community inhabiting an oligotrophic maritime Antarctic fellfield soil. In contrast with studies in vegetated soils at lower latitudes, OTCs increased fungal community alpha diversity (Simpson’s index and evenness) by 102–142% in unamended soil after 5 years. Conversely, OTCs had few effects on diversity in substrate-amended soils, with their only main effects, in glycine-amended soils, being attributable to an abundance of Pseudogymnoascus. The substrates reduced alpha and beta diversity metrics by 18–63%, altered community composition and elevated soil fungal DNA concentrations by 1–2 orders of magnitude after 5 years. In glycine-amended soil, OTCs decreased DNA concentrations by 57% and increased the relative abundance of the yeast Vishniacozyma by 45-fold. The relative abundance of the yeast Gelidatrema declined by 78% in chambered soil and increased by 1.9-fold in irrigated soil. Fungal DNA concentrations were also halved by irrigation in TSB-amended soils. In support of regional- and continental-scale studies across climatic gradients, the observations indicate that soil fungal alpha diversity in maritime Antarctica will increase as the region warms, but suggest that the accumulation of organic carbon and nitrogen compounds in fellfield soils arising from expanding plant populations are likely, in time, to attenuate the positive effects of warming on diversity.

Wide divergence of fungal communities inhabiting rocks and soils in a hyper‐arid Antarctic desert

“…Interestingly, in addition to other abiotic parameters known to determine the abundance of soil fungal taxa in Antarctica, such as soil texture and cation concentrations (Canini et al, 2020, 2021; Connell et al, 2006), soil C and N concentrations also strongly affected the abundances of fungi and, as revealed by the PCA analysis, were discriminant variables separating soil samples. In agreement with studies showing increased abundances of yeasts in nutrient‐amended oligotrophic Antarctic soils (Newsham et al, 2022), two genera of yeasts, Naganishia and Meyerozyma , the main constituents of the soil fungal communities at the three study sites, showed positive correlations with cation concentrations in soil. These data confirm previous studies showing soil cation concentrations affect the richness and composition of Antarctic soil fungal communities (Canini et al, 2020).…”

“…Furthermore, previous studies of soil fungal diversity in Antarctica have typically been carried out using culturing methods (Arenz & Blanchette, 2011;Connell et al, 2008). Many recent studies using cutting-edge molecular techniques have been focused on the Maritime Antarctic (see for example, da Silva et al, 2020;Dur an et al, 2019;Newsham et al, 2021Newsham et al, , 2022Rosa et al, 2020;Santos et al, 2020) or coastal sites in continental Antarctica (Canini et al, 2020;Ji et al, 2016;Siciliano et al, 2014), and with comparatively few studies using these techniques on inner continental Antarctic fungal communities. The handful of molecular mycological studies hitherto carried out in inner continental Antarctica have revealed the dominance of a narrow range of fungal taxa in soils, primarily belonging to Ascomycota and Basidiomycota, with the latter mainly being represented by yeasts (Arenz et al, 2014;Pudasaini et al, 2017;Wei et al, 2016).…”

Rapid Response to Experimental Warming of a Microbial Community Inhabiting High Arctic Patterned Ground Soil

“…We anticipated that, as in vegetated Arctic soils, warming and irrigation would rapidly affect the rates of exchange of greenhouse gases between the atmosphere and soil [ 23 , 24 ]. However, in contrast with the majority of studies on densely vegetated Arctic soils [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], but in accordance with those on barren soils in maritime Antarctica [ 25 , 26 , 27 ], we anticipated rapid treatment effects on the size and composition of the soil microbial community.…”

“…In agreement with previous studies on Arctic soils [ 23 , 44 , 45 , 46 ], we found that a 1 °C rise in summertime near-surface temperature in a sparsely vegetated patterned ground soil on Svalbard increased soil CO 2 efflux and CH 4 consumption rates after 4 years of treatment. However, in contrast with experiments on vegetated soils in the Arctic [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], but in accordance with those on barren maritime Antarctic soils [ 25 , 26 , 27 ], rapid impacts of the warming treatment on the size and composition of the soil microbial community were recorded. Other than a marginally significant positive effect on CO 2 efflux, irrigation had no effects on greenhouse gas flux rates or the soil microbial community.…”

“…At present, the reasons for the differences in the responses to warming of the soil microbial communities in the present and previous empirical studies are not clear. However, the rapid response of the bacterial community to warming in the sparsely vegetated soil studied here is similar to that of microbial communities in barren Antarctic fellfield soils warmed with OTCs, which respond to treatment within 5 years [ 25 , 26 , 27 ]. The relatively rapid response of the microbial community to warming reported here corroborates the view that delays of up to 15 years in microbial responses to elevated temperature in vegetated Arctic soils arise from gradual changes to the biomass and composition of the plant community [ 11 ].…”