Comparable early-stage decomposition but contrasting underlying drivers between surface and cave habitats along an elevational gradient

Decomposition is a major contributor to ecosystem respiration, determining the carbon emission and nutrient cycling rates. Our current understanding of decomposition dynamics and their underlying drivers has mainly focused on surface habitats but largely ignored in subterranean environments. Here we studied abiotic and microbial drivers of early-stage litter decomposition inside and outside caves along an elevational gradient in Tenerife. We found comparable decomposition rates (k) and litter stabilizing factors (S), with contrasting drivers and elevational variation. At the surface, we observed a mid-elevational trend in k, which tended to correlate with water availability, cooler temperatures, nutrient availability, and surface-specific bacterial taxa. In sharp contrast, caves showed no elevational impact nor influence of abiotic parameters and bacterial communities on k. Despite this, we found higher levels of S in caves, which were associated mainly with reduced water availability, lower temperatures and cave-specific bacterial taxa, indicating that conditions in caves are strongly linked with carbon storage. Our findings imply that our current perception of terrestrial habitat-based carbon cycling are underestimating the net carbon budget in areas with caves. Disentangling the role of the environment on decomposition in caves is key to fully characterize their roles in nutrient cycling and to understand how increasing anthropogenic pressures will affect fundamental processes in subterranean ecosystems.info:eu-repo/semantics/publishedVersio

Nutrient-limited subarctic caves harbour more diverse and complex bacterial communities than their surface soil

Background: Subarctic regions are particularly vulnerable to climate change, yet little is known about nutrient availability and biodiversity of their cave ecosystems. Such knowledge is crucial for predicting the vulnerability of these ecosystems to consequences of climate change. Thus, to improve our understanding of life in these habitats, we characterized environmental variables, as well as bacterial and invertebrate communities of six subarctic caves in Northern Norway. Results: Only a minuscule diversity of surface-adapted invertebrates were found in these caves. However, the bacte‑ rial communities in caves were compositionally diferent, more diverse and more complex than the nutrient-richer surface soil. Cave soil microbiomes were less variable between caves than between surface communities in the same area, suggesting that the stable cave environments with tougher conditions drive the uniform microbial communi‑ ties. We also observed only a small proportion of cave bacterial genera originating from the surface, indicating unique cave-adapted microbial communities. Increased diversity within caves may stem from higher niche specialization and levels of interdependencies for nutrient cycling among bacterial taxa in these oligotrophic environments. Conclusions: Taken together this suggest that environmental changes, e.g., faster melting of snow as a result of global warming that could alter nutrient infux, can have a detrimental impact on interactions and dependencies of these complex communities. This comparative exploration of cave and surface microbiomes also lays the founda‑ tion to further investigate the long-term environmental variables that shape the biodiversity of these vulnerable ecosystems.info:eu-repo/semantics/publishedVersio