Abstract
The space-for-time substitution approach provides a valuable empirical assessment to infer temporal effects of disturbance from spatial gradients. Applied to predict the response of different ecosystems under current climate change scenarios, it remains poorly tested in microbial ecology studies, partly due to the trophic complexity of the ecosystems typically studied. The McMurdo Dry Valleys (MDV) of Antarctica represent a trophically simple polar desert projected to experience drastic changes in water availability under current climate change scenarios. We used this ideal model system to develop and validate a microbial space-for-time sampling approach, using the variation of geochemical profiles that follow alterations in water availability and reflect past changes in the system. Our framework measured soil electrical conductivity, pH, and water activity in situ to geochemically define 17 space-for-time transects from the shores of four dynamic and two static Dry Valley lakes. We identified microbial taxa that are consistently responsive to changes in wetness in the soils and reliably associated with long-term dry or wet edaphic conditions. Comparisons between transects defined at static (open-basin) and dynamic (closed-basin) lakes highlighted the capacity for geochemically defined space-for-time gradients to identify lasting deterministic impacts of historical changes in water presence on the structure and diversity of extant microbial communities. We highlight the potential for geochemically defined space-for-time transects to resolve legacy impacts of environmental change when used in conjunction with static and dynamic scenarios, and to inform future environmental scenarios through changes in the microbial community structure, composition, and diversity.
Highlights
Long-term ecological observations provide valuable information for studying the impacts of climate change
We removed thirty-two operational taxonomic units (OTUs) classified as Chloroplast using the SILVA database, leaving a dataset containing 1,101 OTUs for downstream analysis
OTUs affiliated to Actinobacteria, order Solirubrobacterales; Chloroflexi, order Kallotenuales; Deinococcota, order Deinococcales; Acidobacteria, order Blastocaellales, and Abditibacteriota, order Abditibacteriales, were exclusively associated to dry and transition zone soils (Figure 7B and Supplementary Table 3)
Summary
Long-term ecological observations provide valuable information for studying the impacts of climate change. They form excellent resources to detect climate trends and patterns over time, study slow or highly variable ecological processes, validate modeled predictions of change, and support environmental policies (Kratz et al, 2003; Rustad, 2008). Space-for-time substitution approaches, such as ecological chronosequences, rely on the assumption that factors responsible for spatial turnover in species abundance are similar to those responsible for temporal turnover (Pickett, 1989; Wogan and Wang, 2018). To validate the use of this approach to assess the temporal effects of climate change on an ecosystem’s microbiome, a baseline study is required in an ecosystem that lacks trophic complexity and includes well-characterized deterministic gradients of species distribution
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