Rhizosphere priming: a nutrient perspective

Abstract

Rhizosphere priming is the change in decomposition of soil organic matter (SOM) caused by root activity. Rhizosphere priming plays a crucial role in soil carbon (C) dynamics and their response to global climate change. Rhizosphere priming may be affected by soil nutrient availability, but rhizosphere priming itself can also affect nutrient supply to plants. These interactive effects may be of particular relevance in understanding the sustained increase in plant growth and nutrient supply in response to a rise in atmospheric CO2 concentration. We examined how these interactions were affected by elevated CO2 in two similar semiarid grassland field studies. We found that an increase in rhizosphere priming enhanced the release of nitrogen (N) through decomposition of a larger fraction of SOM in one study, but not in the other. We postulate that rhizosphere priming may enhance N supply to plants in systems that are N limited, but that rhizosphere priming may not occur in systems that are phosphorus (P) limited. Under P limitation, rhizodeposition may be used for mobilization of P, rather than for decomposition of SOM. Therefore, with increasing atmospheric CO2 concentrations, rhizosphere priming may play a larger role in affecting C sequestration in N poor than in P poor soils.

Nitrogen mineralization, not N<sub>2</sub> fixation, alleviates progressive nitrogen limitation – Comment on “Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis” by Liang et al. (2016)

“…However, due to the limited spatial extent of plant communities dominated by symbiotic N 2 fixation, the stimulation in BNF suggested by Liang et al (2016) is a special case only and is in agreement with the conceptual model by Rütting and Andresen (2015). In the majority of terrestrial ecosystems, with limited or no BNF, enhanced carbon inputs to the soil under elevated CO 2 stimulate the gross N mineralization rate (Dijkstra et al, 2013;Rütting and Andresen, 2015) in a priminglike mechanism, which can explain the absence of the development of a PNL in N-limited ecosystems (Fig. 2).…”

How a Root-Microbial System Regulates the Response of Soil Respiration to Temperature and Moisture in a Plantation

“…However, other studies have found that the increase of temperature reduced the rhizosphere priming effect [42]. The priming effect is determined by the availability of soil nutrients [43][44]. In general, high soil moisture produces a strong rhizosphere priming effect [45].…”

The Microbial Regulation of Global Biogeochemical Cycles

“…A very active research area in soil microbial ecology is presently how small amounts of labile carbon sources can trigger, or "prime," the decomposition of soil organic matter. A route toward a more general understanding of the regulation of plant-soil interaction for biogeochemistry, that may well facilitate our understanding of "priming effects," could be the incorporation of stoichiometric concepts (Dijkstra et al, 2013;Mooshammer et al, 2014). Stoichiometric variations in the concentration of nutrients, combined with variations in carbon and nutrient demands of different decomposer groups, also seems to be reflected in the degradation rate of plant litter .…”