ID43: Mountain soil biodiversity above the treeline

Abstract ID 799 | Date: 2022-09-14 16:10 – 16:20 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Angel, Roey (1); Doležal, Jiří (2); Dvorský, Miroslav (2); Rehaková, Klara (2)

Elevational diversity gradients of plants and animals are a well-established ecological phenomenon. However, despite some attempts to describe microbial diversity along altitudinal transects, it remains unclear if and to what extent microbes mirror the changes seen in plants and animals. In addition, most studies focused on mountains in temperate regions where temperature decrease with elevation is the primary abiotic gradient affecting biodiversity. We studied the bacterial diversity and population size of various microbial groups along an extreme-high elevation gradient ranging from 4700 to 6450 m.a.s.l in the western Himalayas, where a precipitation gradient exists inversely to the temperature gradient. This leads to the formation of three different vegetation belts: arid, alpine grassland and subnival.

Population densities of bacteria, archaea, fungi and cyanobacteria (determined using qPCR) and alpha diversity estimates for bacteria (determined using Illumina sequencing) all displayed a humped-shape trend peaking at around 5800 m.a.s.l, just below the subnival zone, coinciding with maximum plant diversity. Below this altitude, microorganisms were likely water-limited; they were about ten times less abundant, and the bacterial community was about 30—50% less diverse. Above this altitude, the temperature was likely the critical limiting factor. Population sizes were up to 100 times lower, and the bacteria were up to 70% less diverse. Members of the orders Sphingomonadales, Sphingobacteriales and Solirubrobacterales were abundant throughout the gradient and with Burkholderiales prevailed in the subnival soils, similarly to soils from soils hot and cold deserts. In contrast, lower elevations were dominated by Rhizobiales, Rhodospirillales, Micrococcales and Cytophagales. However, distinct communities dominated the different vegetation belts.

Taxa-elevation relationship and phylogenetic relatedness analyses showed only a little turnover of species along the gradient within each belt, especially within the alpine and subnival ones, and a strong deterministic selection, but a reasonably large one between the belts.

Our results show that soil microbes react to contrasting gradients of precipitation and temperate similarly to plants and demonstrate clear and predictable changes in dominant taxonomic groups with increasing altitude. In addition, we demarcate the importance of Sphingomonadales, Sphingobacteriales, and Solirubrobacterales as pioneer species dominating deglaciated soils.

Abstract ID 591 | Date: 2022-09-14 16:20 – 16:30 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Praeg, Nadine (1); Galla, Giulio (2); Rzehak, Theresa (1); Colla, Filippo (3,4); Seeber, Julia (3,4); Hauffe, Heidi C. (2); Illmer, Paul (1)

Biodiversity is a central keyword of the 21^st century and has been gaining increasing attention with regards to the stability and vulnerability of soil ecosystems, especially in the light of global change. The diversities of soil microbial communities are major regulators of fundamental ecosystem processes, such as organic matter decomposition, nutrient cycling and gaseous fluxes. Within the soil food web, archaea, bacteria and fungi interact with each other, with organisms of the soil micro- and mesofauna (such as nematodes and collembolans), as well as with soil macrofauna (earthworms, insects, spiders) and plants.

Alpine pastures have been traditionally managed for centuries and harbor specific soil animal and microbial communities; therefore, the concept of an “intact soil” and the definition of “disturbance” is of special concern in these sites. In the inner-Alpine EUREGIO region (Austria/Italy), Alpine pastures provide one of the dominant landscapes and are the basis for mountain agriculture, and a source of agrifood, biodiversity and tourism. Although we know that some soil functions depend on land management (e.g. capacity to sequester carbon), knowledge of the interactions and co-occurrences of microbial communities is critical and virtually non-existent.

The EUREGIO project MICROVALU “Evaluating microbial diversity in alpine pastures” has developed specific protocols to compare the prokaryotic and fungal community composition of different sample types, including bulk soil samples, rhizosphere soil of Carex spp. and Festuca spp., members of the micro- (nematodes), meso- (collembolans), and macrofauna (earthworms, ground and rove beetles), as well as fecal samples of wild mammals and domestic livestock at replicated sites along an elevational gradient from below to above the treeline (1000-2500 m a.s.l.). The elevational gradient is used as a proxy to determine the influence of climate on the respective sample-specific microbiota and the overlapping microbiota between sample types.

Our results indicate that soil, rhizosphere and faunal samples each have a unique microbial community composition, but also that these microbiota overlap to different degrees, depending on functional traits, trophic relationships and elevation. In addition to a comprehensive soil and meteorological dataset, the study is providing new information on the interactions of microorganisms in the soil-food web and their responses to climate-related environmental properties.

Abstract ID 674 | Date: 2022-09-14 16:30 – 16:40 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Steinwandter, Michael (1); Von Spinn, Julian (2); Seeber, Julia (1,2)

Since the 2010s, the number of studies on soil fauna studies increased considerably. However, still few studies focus on high alpine areas. Here we present a comprehensive pitfall trap survey on ground-dwelling invertebrates in alpine grazed grassland spanning from 1500–3000 m along three distinct elevation gradients. The study was conducted in the European Central Alps in the LTSER area “Val Mazia/Matschertal”, South Tyrol, Italy. The aim was to investigate (i) the abundance of the soil fauna and especially those of ground-dwelling spider species, (ii) changes in community composition with elevation, and (iii) seasonal community dynamics. We are focusing on the 3000-m sites where soil fauna data is very rare.

On each of the 12 plots (3 for each 500-m step), we installed 3 pitfall traps per sampling period: 3x for 2 weeks at the lower and 2x for 3 weeks at the higher sites (in sum all were active for 6 weeks). All taxa were identified to family level where possible (Coleoptera, Myriapoda, Diptera larvae); Araneae to species level. Additionally, soil properties, soil temperature and humidity and the vegetation were surveyed.

First results show high and consistent taxa numbers for the 2500–3000-m sites, with on average 26.00 (±1.00) and 23.67 (±1.73) taxa per sample, respectively. In contrast, on the lower sites considerably lower and variable numbers of taxa were found (e.g., at the 2000-m sites 19.67 ±4.51).

Drawing first conclusions, we are surprised by the high macrofauna diversity in the high alpine sites, and especially by the high variable and species-poor community at the 2000-m sites. This is confirmed, for example, by the millipedes Julidae. They were almost absent in former investigations, but were recorded in many 3000-m pitfall traps along with Craspedosomatidae; the snow-rich winter 2020/2021 might have benefited their development. On the lower sites, Coleoptera show their highest activity in the peak of summer, along with mesofauna groups (Acari, Collembola). As already a highlight, we could find one new spider species for South Tyrol at the 2500-m sites (the Salticidae Pellens lapponicus (Sundevall, 1833)) and expect further new findings for these understudies high alpine ecosystems.

Abstract ID 209 | Date: 2022-09-14 16:40 – 16:50 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Mazel, Florent (1); Malard, Lucie (1); Lara, Enrique (2); Guisan, Antoine (1)

Protists are abundant and play key trophic functions in soil. Documenting how their trophic contributions vary across large environmental gradients is essential to understand and predict how biogeochemical cycles will be impacted by global changes. Here, using amplicon sequencing of environmental DNA in open habitat soil from 161 locations spanning 2600 m of elevation in the Swiss Alps (from 400 m to 3000 m), we found that, over the whole study area, soils are dominated by consumers, followed by parasites and phototrophs. In contrast, the proportion of these groups in local communities shows large variations in relation to elevation. While there is, on average, three times more consumers than parasites at low elevation (400-1000 m), this ratio increases to twelve at high elevation (2000-3000 m). This suggests that the decrease in protist host biomass and diversity towards mountains tops impact protist functional composition. Furthermore, the taxonomic composition of protists that infect animals was related to elevation while that of protists that infect plants or of protist consumers was related to soil pH. This study provides a first step to document and understand how soil protist functions varies along the elevational gradient.

Abstract ID 215 | Date: 2022-09-14 16:50 – 17:00 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Taylor, Andy Forsyth Scott (1,2); Fielding, Debbie (1); Freitag, Thomas E (1); Oddi, Ludovica (3); Robinson, Lucinda (1); Van Paassen, José (4); White, Duncan (1); Britton, Andrea (1)

High spatial heterogeneity of abiotic conditions and plant community composition are important and well-recognised features of alpine ecosystems, contributing to their status as hotspots of biodiversity. Topography and altitude interact with snow cover and meso-climate, leading to steep gradients and high spatial variability in abiotic conditions and the development of heterogeneous mosaics of plant communities. Heterogeneity is therefore an intrinsic and vital component for the functioning of alpine systems. However, most ecological importance attributed to heterogeneity is derived from above ground vegetation studies, with much less known regarding soil biodiversity distribution. Here, we report on the spatial congruence across six kingdoms of soil biodiversity associated with vegetation mosaics in an alpine ecosystem on Ben Avon in the eastern Highlands of Scotland, UK. Fifteen plots (9 in late snow beds) were sampled from each of seven distinct vegetation types for a range of environmental, chemical and biological parameters. We analysed soil communities beneath the vegetation mosaic using DNA metabarcoding approaches, using the 18S, 16S and ITS regions, which provided distribution data on the Animalia, Archaea, Chromista, Eubacteria, Fungi, and Plantae kingdoms. Data were also gained from the kingdom Protozoa, but diversity was too low to allow any spatial analyses.

A total of 13113172 reads were generated across the three barcodes, giving 773 Animalia, 98 Archaea, 741 Chromista, 16473 Eubacteria, 3415 Fungi, and 207 Plantae distinct entities. The Plantae were restricted to Chlorophyta (green algae). The 18S eukaryotic data also included 1524 unknowns which could not be assigned to any kingdom.

Ordination analyses of the community data from each of the six major kingdoms recovered by the metabarcoding demonstrated strong to very strong spatial segregation of communities, corresponding to the highly distinctive plant assemblages above ground. The challenge will now be to distinguish between the biological and abiotic drivers maintaining this remarkable congruity across the breadth of classified biodiversity.

Abstract ID 232 | Date: 2022-09-14 17:00 – 17:10 | Type: Oral Presentation | Place: SOWI – Lecture hall HS1 |

Kashyap, Priyanka; Uniyal, Virendra Prasad

Earth’s climate has been changing and evolving, which can be seen by comparing the status of the Indian Himalayan Region (IHR). Changes in Snow water equivalent, snowmelt, and glacier melt runoff have altered the soil structure and fauna, especially soil nematodes at various trophic levels. Soil nematode community structure influences the soil ecosystem functioning as they play an important role in some crucial soil ecological processes and are considered a potential instrument for assessing soil conditions and biomonitoring system. Keeping this in consideration, an experimental study using an Open top chamber (OTC) was conducted in high altitude region of Gangotri valley in Western Indian Himalaya to understand the effect of altered temperature on abundance, diversity, and metabolic footprint of soil inhabiting nematodes.

To assess the effect of temperature on soil nematodes of the study area, soil cores were collected from experimental (OTC) and control plots with its replicates. Nematodes were extracted, identified up to the genus level, allotted to trophic groups and ecological indices were calculated. Data loggers were installed in the OTC and the adjacent control plots at the height of 14-15 cm above and 5 cm below the surface for recording air and soil temperature every hour.

Soil and the air temperature was ~1 °C higher inside OTC compared to the control plot for almost throughout the year except for August- September, and the temperature difference was nearly 1.9 °C higher inside OTC in the second year. Forty two genera belong to 20 families, and eight orders were recorded for the study region. Nematode community structure analysis showed that bacterial feeder abundance is higher in OTC. Acrobeloides and Rhabdolaimus are the only bacterial feeder whose density significantly increased by the elevated condition of OTC. Predatory nematode abundance was slightly lower in OTC compared to the control plot. Maturity Index (an indicator of disturbance) was lower in OTC and significantly differed. Dissimilarity tests showed that nematode communities in OTC were significantly different from the control plots. The soil moisture was different among the treatment and control plots, suggesting that warming indirectly affects nematode diversity by affecting soil moisture in the treatment plot. As a result, it can be hypothesized that warming-induced soil moisture could be the primary reason for differences in nematode responses between OTC and Control. The experimental baseline information regarding nematode community structure and nematode-specific indices can be used as soil health indicators and long-term climate change impact assessment studies.

Abstract ID 769 | Date: 2022-09-14 17:45 – 17:47 | Type: Poster Presentation | Place: SOWI – Garden |

Rzehak, Theresa (1); Praeg, Nadine (1); Galla, Giulio (2); Colla, Filippo (3,4); Seeber, Julia (3,4); Hauffe, Heidi C. (2); Illmer, Paul (1)

The soils of Alpine pastures provide diverse habitats for animals, plants and microorganisms and are known as hotspots for biodiversity. In particular, soil microbes have a significant role in soil function. The international project MICROVALU is evaluating the microbial diversity in Alpine pastures by analyzing different components of the soil food web including soil, rhizosphere soil, invertebrate fauna and fecal samples of dominant above-ground mammals and tries to provide a more complete understanding of the relationship between soil organisms and their effect on soil processes.

The association of plants with plant growth-promoting microbes (PGPM) is substantial for plants to cope environmental stress, e.g. caused by climate change, and is essential for fruitful and sustainable agriculture in Alpine regions. Therefore, in addition to assessing overall microbial diversity patterns, we are focusing on possible driving factors for the abundance and composition of PGPM that live in close association with the roots of plants. These organisms provide the plant with beneficial services ranging from nitrogen fixation and phosphate solubilization, to phytopathogen suppression via antibiotic production, resulting in better plant growth, faster germination, enhanced root growth, and higher resistance against abiotic and biotic stress. Since the impact of factors like elevation, temperature, drought and interactions and/or transmissions via the soil fauna on PGPM is limited, this particular study is also ground-breaking.

For this study, samples from bulk soil, rhizosphere soil of two common plant genera in Alpine pastures (Carex spp. and Festuca spp.), belowground fauna (micro-, meso- and macrofauna) and fecal pellets of above ground fauna (wild animals and domestic livestock), were collected along an elevational gradient of an inner-Alpine valley from below to above the treeline (1000-2500 m a.s.l.). Microbial abundance, community composition, and diversity were determined in all sample types, and special focus is now being paid on the abundance and diversity of PGPM.

Our results will identify the associations of PGPM in the rhizosphere and the associations and possible transmission of PGPM between soil and soil animals in Alpine pastures under changing environmental conditions.

Abstract ID 278 | Date: 2022-09-14 17:47 – 17:49 | Type: Poster Presentation | Place: SOWI – Garden |

Mandolini, Edoardo; Probst, Maraike; Telagathoti, Anusha; Rodriguez-Rojas, Miguel; Peintner, Ursula

Soil formation is the result of a complex network of biological, chemical, and physical processes. When ice fronts of glaciers retreat, they expose large expanses of deglaciated forefield, which become colonized by bacteria and fungi. These environments provide unique chronosequences of different soil developmental stages and are ideal for studying the role of keystone microbes, whose interaction promotes mineral soil fertility and pioneer plant growth. Very few studies have investigated the soil microbial community in the winter season and, although estimates suggest that cold-adapted bacteria and fungi are very active under the snow-cover, the quality of their diversity and interactions remains largely unexplored. In this study, we investigated the diversity of both the fungal and bacterial winter communities at the early stages of soil development (0-25 years) in four receding glaciers of the Alps, namely Hallstätter (AU), Marmolada (ITA), Griessen (CH), and Tsanfleuron (CH). These sites are characterized by a calcareous bedrock (i.e., CaCO₃). Therefore, they differ from other alpine glaciers already studied mainly by a soil pH close to neutral-basal values and lower water and nutrient retention. Our results show low nutrient concentrations, but increasing with soil maturation. Both soil fungal and bacterial richness increased along the developmental gradient. Most of the microbial taxa detected were unique for the different glacier forefields nevertheless, a shared core community existed. Based on network analysis, the developmental stage of the soil influenced the bacterial-fungal interactions, with fewer interacting nodes in late succession sites. We also speculate a change in trophic interactions among microbes with an increase in competition for nutrients and ecological niche in late succession, compared to more mutualistic relationships in earlier stages. Taken together, our results emphasize the importance of cold-adapted fungal-bacterial interactions to the development of soil in recently deglaciated ecosystems.