Plant diversity - Sustainable adaptation

This project investigated and compared the ability of monocultures and mixtures to maintain ecosystem function under control and drought conditions.

Two field experiments in Switzerland showed clear over-yielding of forage from mixtures compared to monocultures under both control and drought conditions. Novel soil tracer techniques were developed and applied in this project (see picture with sampling grid), and provided some evidence for vertical belowground niche complementarity. Differences between deep- and shallow-rooting species tended to be larger under drought conditions, when resources were most limited. In general, species moved their nutrient and water uptake to deeper soil layers under drought conditions. The plant community in some cases affected the depth of resource uptake; however, we could find no evidence for increased niche complementarity in monocultures compared to mixtures.

15N methods showed that facilitation between legumes and non-legumes increased total N yields in mixtures compared to monoculture and showed that legumes regulate their activity of SNF to close the gap between their N-demand for growth and the availability of N from non-symbiotic sources in conditions with low availability of soil N.

Both monoculture and mixture yield and nutrient uptake was strongly affected by the drought treatment, but the benefit (overyielding) of the mixtures relative to monocultures was maintained under drought conditions. There was no conclusive evidence that deep-rooting species were less sensitive to drought stress, but under moderate drought stress, the legumes were less affected than the non-legumes.

For further information, contact Dr John Finn john.finn(at)teagasc.ie

Further information

Hoekstra, N.J., Suter, M., Finn, J.A., Husse, S. and Lüscher, A. 2015. Do belowground vertical niche differences between deep- and shallow-rooted species enhance resource uptake and drought resistance in grassland mixtures? Plant and Soil (in press)

Hoekstra NJ, Finn JA, Buchmann N, Gockele A, Landert L, Prill N, Scherer-Lorenzen M, Lüscher A (2014) Methodological tests of the use of trace elements as tracers to assess root activity. Plant and Soil, 380: 265-283.

Hoekstra, N.J., Finn, J.A., Lüscher, A. (2014) The effect of drought and interspecific interactions on the depth of water uptake in deep- and shallow-rooting grassland species as determined by δ18O natural abundance. Biogeosciences, 11: 4493-4506.

Hoekstra NJ, Finn J, Lüscher A (2013) Nutrient uptake in soil niches affected by plant species and drought stress. Agricultural Research Forum 2013, Tullamore, Ireland.

Hoekstra NJ, Finn J, Lüscher A (2013) Nutrient uptake in soil niches affected by plant species and drought stress. Grassland Science in Europe 18, Akureyri, Iceland.

Hofer D, Suter M, Hoekstra N, Buchmann N, Lüscher A (2013) N2 fixing legumes in intensively managed grassland are less affected by drought than non-fixing species. Plants in a Changing Climate – Plant Science Centre Symposium 2013, Zurich.

Hoekstra NJ, Landert LA, Finn J, Lüscher A (2012) Assessment of tracer methods for identifying belowground niche differentiation in grassland. Grassland Science in Europe 17.

Acknowledgements

N. J. Hoekstra was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments were supported by the European Community’s Seventh Framework Programme (FP7/2007–2013) under the grant agreements FP7-266018 (AnimalChange) and FP7-244983 (MultiSward).