Abstract
Summary 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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions. 3. Both cellulose and phenolic‐rich root C additions inhibited D. caespitosa growth in field microcosms, relative to controls. N additions reversed the negative effects of cellulose on plant growth but did not reverse the inhibitory effects of phenolic‐rich C additions. A companion soil incubation experiment showed that both types of C addition reduced N availability relative to controls, and there was a strong negative correlation between N availability and substrate‐induced soil respiration. 4. Our results indicate that root C inputs to soil can have substantial, negative effects on plant growth. Reduced plant growth was likely to be caused by (i) indirect interactions between root C and soil microbes lowering plant N supply; and (ii) a mechanism independent of N supply, possibly involving allelopathic effects of G. rossii phenolic compounds on D. caespitosa root growth. 5. Synthesis. Fine root inputs to soil (i.e. phenolic‐rich C and cellulose C) reduced a neighbouring plant’s growth and the chemical composition of the root C influenced whether growth inhibition could be overcome by increased plant N supply. Negative effects of phenolic‐rich root inputs on plant growth could be an under‐appreciated factor structuring plant communities, particularly in N‐limited systems dominated by phenolic‐rich species.
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Claims 8
Claim · model-written summary
Cellulose root carbon inhibited Deschampsia growth relative to controls.
Verbatim
e0“Both cellulose and phenolic‐rich root C additions inhibited D. caespitosa growth in field microcosms, relative to controls.”
Claim · model-written summary
Phenolic-rich root carbon inhibited Deschampsia growth relative to controls.
- Taxon
- D. caespitosae0
- Treatment
- phenolic‐rich root C additionse0
- Interactor
- G. rossii
.jpg?width=60)
Geum rossiie1othere0 - Outcome
- D. caespitosa growthe0
- Direction
- inhibitede0
- Comparator
- controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Both cellulose and phenolic‐rich root C additions inhibited D. caespitosa growth in field microcosms, relative to controls.”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
Nitrogen addition reversed cellulose-mediated growth inhibition.
Not reportedComparator
Verbatim
e0“N additions reversed the negative effects of cellulose on plant growth”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
Nitrogen addition did not reverse phenolic-rich carbon growth inhibition.
- Taxon
- D. caespitosae1
- Treatment
- N additionse1
- Outcome
- inhibitory effects of phenolic‐rich C additionse0
- Direction
- did not reversee0
Not reportedComparator
Verbatim
e0“did not reverse the inhibitory effects of phenolic‐rich C additions.”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
Both carbon additions reduced soil nitrogen availability.
Verbatim
e0“both types of C addition reduced N availability relative to controls”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
Soil nitrogen availability was strongly negatively correlated with substrate-induced respiration.
Verbatim
e0“there was a strong negative correlation between N availability and substrate‐induced soil respiration.”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
Root carbon likely reduced growth through microbial restriction of plant nitrogen supply.
Verbatim
e0“indirect interactions between root C and soil microbes lowering plant N supply”
e1“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 plant N supplies. We predicted that this effect could be overcome by fertilization with N. We also hypothesized that G. rossii root phenolics could allelopathically inhibit D. caespitosa growth, and we predicted that direct, allelopathic inhibition would not be reversible with N additions.”
Claim · model-written summary
A nitrogen-independent mechanism possibly involving Geum phenolics inhibited Deschampsia roots.
- Taxon
- D. caespitosae0
- Interactor
- G. rossiiGeum rossiie0other
- Compound
- phenolic compoundse0
- Outcome
- D. caespitosa root growthe0
- Qualifier
- possiblye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“possibly involving allelopathic effects of G. rossii phenolic compounds on D. caespitosa root growth.”