Plant diversity and density predict belowground diversity and function in an early successional alpine ecosystem

Abstract

Despite decades of interest, few studies have provided evidence supporting theoretical expectations for coupled relationships between aboveground and belowground diversity and ecosystem functioning in non-manipulated natural ecosystems. We characterized plant species richness and density, soil bacterial, fungal and eukaryotic species richness and phylogenetic diversity (using 16S, ITS, and 18S gene sequencing), and ecosystem function (levels of soil C and N, and rates of microbial enzyme activities) along a natural gradient in plant richness and density in high-elevation, C-deficient soils to examine the coupling between above- and belowground systems. Overall, we observed a strong positive relationship between aboveground (plant richness and density) and belowground (bacteria, fungi, and non-fungal eukaryotes) richness. In addition to the correlations between plants and soil communities, C and N pools, and rates of enzyme activities increased as plant and soil communities became richer and more diverse. Our results suggest that the theoretically expected positive correlation between above- and belowground communities does exist in natural systems, but may be undetectable in late successional ecosystems due to the buildup of legacy organic matter that results in extremely complex belowground communities. In contrast, microbial communities in early successional systems, such as the system described here, are more directly dependent on contemporary inputs from plants and therefore are strongly correlated with plant diversity and density.

Contrasting biogeographic patterns of bacterial and archaeal diversity in the top- and subsoils of temperate grasslands

“…Among the variables reflecting the effects of vegetation, plant species richness has a particularly strong negative effect on bacterial diversity (Table S2). This result stands in contrast with previous studies that reported either a positive correlation between bacterial diversity and plant diversity in the Rocky Mountains in Colorado, USA (16) or a neutral relationship in global temperate grassland (15, 50). For clades with different functions, the diversity of most oligotrophic clades is negatively correlated with plant species richness, consistent with previous studies (43, 45).…”

“…For clades with different functions, the diversity of most oligotrophic clades is negatively correlated with plant species richness, consistent with previous studies (43, 45). In contrast, the diversity of most copiotrophic clades (such as Betaproteobacteria ) is positively correlated with plant species richness (Table S1) (16, 50). Those results further corroborate the dominance of oligotrophic bacterial clades in infertile grassland.…”

“…Soil microbial diversity is influenced by a wide array of variables including edaphic properties (e. g. soil pH and nutrients) (11-14), vegetation (15, 16), contemporary climate (17-19) and historical climate change (20-22), etc. Compared to the topsoil, these variables may have differential controls on microbial diversity in the subsoil due to varied ranges and different orders of importance for these factors.…”

Soil Microbial Networks Shift Across a High-Elevation Successional Gradient

“…We classified plots as early, mid, or late succession by running a PCA of environmental and plant variables previously determined to change over successional gradients in alpine areas (Bekku et al, 2004;Schmidt et al, 2008;Porazinska et al, 2018)…”

“…Microbes are important regulators of ecosystem function, and much research has been directed at testing how soil microbial composition and diversity shift along environmental gradients. Work, thus far, has identified many important abiotic and biotic drivers that structure the composition and diversity of microorganisms in the soil, including pH, salinity, climate, soil nutrients, plant diversity, and plant functional traits (Fierer and Jackson, 2006;Lozupone and Knight, 2007;Nemergut et al, 2010;de Vries et al, 2012;Porazinska et al, 2018). However, how interactions among microbial taxa change across the landscape is much less well understood (Nemergut et al, 2013).…”