Abstract
The facilitating effect of the exudation of carbon (C) compounds from roots on rhizospheric processes has been shown in controlled experiments; however, it still remains unclear how important this pathway of C from plants to the soil may be in energy and nutrient processes in grazed grasslands under natural conditions. Root exudation may be a particularly important C pathway in grazed grasslands and help promote positive feedbacks between large herbivores and plants. In this study we performed a 13C pulse-chase experiment on plots that were clipped or left unclipped in a mesic grassland in Yellowstone National Park. The dominant grass species in the plots was Poa pratensis and it was used to measure the effect of defoliation on root C exudation, the rhizospheric microbial community, and feedbacks on plant nutrient uptake over a time period of 24-72 h. Defoliation stimulated C exudation from roots by 1.5-fold, which concomitantly increased rhizospheric microbial biomass by the same factor. The facilitating effects of defoliation on rhizospheric processes resulted in positive feedback on soil inorganic N pools and leaf N content, which increased by 1.2- and 1.5-fold respectively. Changes in soil inorganic N pools during the experiment indicated that the effect of the C flush on the rhizospheric decomposer community of defoliated plants resulted in a 5-fold increase in rhizospheric daily net N mineralization rate. These findings demonstrate that in a natural grassland community defoliation-induced stimulation of C exudation stimulates rhizospheric N-mineralization which ultimately benefits defoliated plants. The results also indicate the important role that short-term root-rhizospheric microbe interactions play in the C and N processes in grazed grasslands.
Original language | English (US) |
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Pages (from-to) | 2865-2873 |
Number of pages | 9 |
Journal | Soil Biology and Biochemistry |
Volume | 40 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2008 |
Keywords
- Decomposition
- Defoliation
- Organic matter
- Poa pratensis
- Rhizosphere
ASJC Scopus subject areas
- Microbiology
- Soil Science