Relative contribution of high and low elevation soil microbes and nematodes to ecosystem functioning
The metabolic theory of ecology predicts how metabolism controls ecological processes at the level of individuals, populations, and ecosystems. For instance, the amount of energy and organic matter that is circulated within ecosystems is largely dependent on soil nutrient recycling which, in turn, is driven by how metabolically active are the soil microbial and animal communities. Communities living along elevation gradients are affected by resource availability and environmental severity, which should directly affect their metabolic activity. Hence, elevation gradients represent excellent tools in ecological research for measuring the direct effect of climate adaptation of soil communities, and their relative effect on ecosystem functioning. In this study, we investigated the differentiation of soil microbial and nematode communities from the lower hilly to the sub-alpine environments. Specifically, by adding soil microbial and nematode communities that originated from low and high elevations to soils and vegetation communities at the two contrasted elevations, it was possible to assess the effect of climate adaptation on soil respiration and vegetation productivity. First, however, we needed to characterize the naturally occurring taxonomic and functional diversity of soil microbes and nematodes. By doing so, we observed reduced microbial diversity and activity at high elevation; specifically, high elevation microbial communities were less efficient in degrading a variety of carbon sources. Additionally, through nematode communities’ functional characterization, we found increased fungal-dominated versus bacterial-dominated energy channels at high elevation, indicating slower organic matter decompositions
processes. Then, with common garden experiments at high and low elevations, we observed that soil respiration was higher with soil biota originating from low elevation, especially at the low-elevation site. On the other hand, we found little effect of the origin of soil biota on plant biomass accumulation over the growing season. To summarize, our findings suggest that climate change, by spurring organisms’ upward expansion, will probably have a limited effect on plant growth, but by inducing more organic matter degradation though faster innate metabolic activity of low-elevation soil microbes, it will indirectly positively influence the rate of nutrient cycling and carbon fluxes from the soil to the atmosphere.
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