INTERACTIVE EFFECTS OF PLANT SPECIES DIVERSITY AND ELEVATED CO₂ON SOIL BIOTA AND NUTRIENT CYCLING

Abstract

Terrestrial ecosystems consist of mutually dependent producer and decomposer subsystems, but not much is known on how their interactions are modified by plant diversity and elevated atmospheric CO2 concentrations. Factorially manipulating grassland plant species diversity and atmospheric CO2 concentrations for five years, we tested whether high diversity or elevated CO2 sustain larger or more active soil communities, affect soil aggregation, water dynamics, or nutrient cycling, and whether plant diversity and elevated CO2 interact. Nitrogen (N) and phosphorus (P) pools, symbiotic N2 fixation, plant litter quality, soil moisture, soil physical structure, soil nematode, collembola and acari communities, soil microbial biomass and microflora community structure (phospholipid fatty acid [PLFA] profiles), soil enzyme activities, and rates of C fluxes to soils were measured. No increases in soil C fluxes or the biomass, number, or activity of soil organisms were detected at high plant diversity; soil H2O and aggregation remained unaltered. Elevated CO2 affected the ecosystem primarily by improving plant and soil water status by reducing leaf conductance, whereas changes in C cycling appeared to be of subordinate importance. Slowed-down soil drying cycles resulted in lower soil aggregation under elevated CO2. Collembola benefited from extra soil moisture under elevated CO2, whereas other faunal groups did not respond. Diversity effects and interactions with elevated CO2 may have been absent because soil responses were mainly driven by community-level processes such as rates of organic C input and water use; these drivers were not changed by plant diversity manipulations, possibly because our species diversity gradient did not extend below five species and because functional type composition remained unaltered. Our findings demonstrate that global change can affect soil aggregation, and we advocate that soil aggregation should be considered as a dynamic property that may respond to environmental changes and feed back on other ecosystem functions.

Changes in soil microbial substrate utilization in response to altered litter diversity and precipitation in a Mediterranean shrubland

“…Several studies evaluated the response of soil microbial properties to plant diversity (e.g., Eisenhauer et al 2010;Milcu et al 2013) or to climate change factors (in the Mediterranean context, see Bérard et al, 2012;Pailler et al 2014;Yuste et al 2014). However, very few studies addressed the combined effects of plant diversity and climate change factors (Niklaus et al 2007;Bloor and Bardgett 2012;Eisenhauer et al 2013;Vogel et al 2013). A synthesis of 12 studies with orthogonal manipulations of global environmental change factors and plant diversity (Takhur et al 2015) showed that effects of environmental change factors (such as drought or nutrient enrichment) and of plant diversity on the soil microbial biomass were independent with no evidence for interactions.…”

Belowground heathland responses after 2 years of combined warming, elevated CO2 and summer drought

“…Warming may consequently initiate a belowground shift in the primary producer controlled food-chain, based on plant litter amount and chemical composition (Graglia et al 2001;Hansen et al 2006;Briones et al 2009;Niklaus et al 2007). Due to changes in these substrates, shifts in soil microbial communities may occur (Hamer and Marschner 2002;Chung et al 2007).…”

Soil Biota and Plant Invasions: Biogeographical Effects on Plant–Microbe Interactions

“…Some experimental studies have found no relationship between plant species diversity and microbial diversity (Gastine et al 2003 ;Porazinska et al 2003 ;Niklaus et al 2007 ). Other experiments have found that plant diversity correlates positively with bacterial composition or diversity (Gr ü ter et al 2006 ;Wardle et al 1999 ;see Wardle 2002 ).…”