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? Rhizodeposition, or the addition of C from roots to soil C pools, is expected to increase if net primary production is stimulated and some excess C is allocated below-ground. We investigated the effects of 5 yrs of elevated CO2 on below-ground C dynamics in a native, C3?C4 grassland ecosystem in Colorado, USA. ? Cylinder harvests following each growing season and monolith excavation at the end of the experiment provided data on root biomass, root C : N ratios, and root and soil ?13C values. We applied an isotopic mixing model to quantify new soil C inputs on elevated and ambient CO2 treatments. ? Root biomass increased by 23% and root C : N ratios increased by 26% after 5 yrs of elevated CO2. Species-specific...
1. Plant carbon (C) and nitrogen (N) inputs to soil interact with microbes and abiotic factors like climate and pH to influence soil fertility and plant productivity. Although root exudates and root litter are important factors affecting the cycling of nutrients critical to plant growth, many studies remain focused on effects of above-ground litter inputs. 2. Using two species that co-dominate alpine moist meadows as a model system (the phenolic-rich forb Geum rossii, and the fast-growing grass Deschampsia caespitosa), we asked whether C from G. rossii fine roots could reduce D. caespitosa growth. We hypothesized that root C would indirectly reduce D. caespitosa growth by stimulating soil microbes, thus restricting...
1 Phenolics are an important, biologically reactive component of the carbon (C) pool that moves from plants to soil. Once in soil, phenolics can regulate plant?soil feedbacks because of their influence on soil nitrogen biogeochemistry. 2 Roots are a largely overlooked potential source of below-ground phenolic C. We examined phenolic fluxes from plants to soil in an alpine ecosystem, where phenolics are associated with slow rates of nutrient cycling. Using a phenolic-rich forb (Acomastylis rossii) and a grass with low tissue phenolics (Deschampsia caespitosa), we asked whether leaves, leaf litter or roots are the dominant source of soil phenolics during the growing season. We also determined whether the composition...
The rhizosphere differs from the bulk soil in a range of biochemical, chemical and physical processes that occur as a consequence of root growth, water and nutrient uptake, respiration and rhizodeposition. These processes also affect microbial ecology and plant physiology to a considerable extent. This review concentrates on two features of this unique environment: rhizosphere geometry and heterogeneity in both space and time. Although it is often depicted as a soil cylinder of a given radius around the root, drawing a boundary between the rhizosphere and bulk soil is an impossible task because rhizosphere processes result in gradients of different sizes. For instance, because of diffusional constraints, root uptake...


    map background search result map search result map Rhizodeposition stimulated by elevated CO2 in a semiarid grassland Rhizodeposition stimulated by elevated CO2 in a semiarid grassland