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Competitive interactions between two meadow grasses under nitrogen and phosphorus limitation
Article first published online: 5 MAR 2010
DOI: 10.1111/j.1365-2435.2010.01692.x
© 2010 The Authors. Journal compilation © 2010 British Ecological Society
Additional Information
How to Cite
Venterink, H. O. and Güsewell, S. (2010), Competitive interactions between two meadow grasses under nitrogen and phosphorus limitation. Functional Ecology, 24: 877–886. doi: 10.1111/j.1365-2435.2010.01692.x
Publication History
- Issue published online: 13 JUL 2010
- Article first published online: 5 MAR 2010
- Received 23 September 2009; accepted 14 January 2010Handling Editor: Gareth Phoenix
Keywords:
- Agrostis capillaris;
- Alopecurus pratensis;
- competition;
- N : P ratio;
- nitrogen;
- phosphorus;
- pre-emption hypothesis;
- N : P stoichiometry
Summary
1. Different grass species dominate grasslands fertilized with nitrogen (N) or phosphorus (P), possibly due to the impact of N : P stoichiometry on competitive interactions. How species compete for nutrients, and whether the mechanisms are similar for N and P, is still not fully understood.
2. We investigated whether the outcome of competition between Alopecurus pratensis and Agrostis capillaris depends on N : P stoichiometry, and on the ability to acquire supplied N or P. Monocultures and mixtures of the two species were grown in pots at nine combinations of N and P supply (N : P ratios 1·7, 15 and 135, all at three supply levels). After 3 months, we determined plant biomass, morphological traits and nutrient concentrations of plant tissues.
3. N : P supply ratios had similar effects on the growth of the two species but contrasting effects on their competitive strength, as assessed by comparing growth in competition to growth in monoculture: Alopecurus was the stronger competitor under N limitation (N : P ratio 1·7), whereas Agrostis was an equal or stronger competitor under P limitation (N : P ratio 135). This result resembled patterns of species distribution observed in the field.
4. The strong competitive response of Alopecurus at the low N : P supply ratio was associated with a high investment in root biomass and root length, and a high nitrogen productivity. The competitive response of Agrostis at the high N : P supply ratio was associated with low root mortality and high root phosphatase activity.
5. Our results obtained under N limitation support the pre-emption theory in which plants with the highest root length are able to acquire more N from the soil than their competitors, and therefore can suppress their growth. Under P limitation, however, plant investment in root length could not explain competitor suppression. Here, other factors important in competition for P, such as mycorrhizal hyphal length, root longevity, or exudation rates of P releasing compounds, merit investigation.