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Permanent grassland productivity can be estimated using simple variables

Variables that broadly explain seasonal differences in biomass production and forage nutritional value in permanent grasslands are the taxonomic composition of the plant community, the phenological stages of the different forage grasses*, and forage dry matter content.

Parcel of permanent grassland located in the Marais Poitevin marshland, which is being monitored as part of a CASDAR project. © INRA
By Sylvie André, translated by Jessica Pearce
Updated on 01/25/2016
Published on 01/07/2016

To understand the economic and environmental benefits that livestock systems derive from permanent grasslands, it is important to better characterize the variables underlying grassland productivity. The goal of the research described here is to determine the degree to which vegetative characteristics predict biomass production and forage nutritional value along broad gradients of soil and climate conditions and as a function of different agricultural practices.

Accurately modelling grassland productivity

Using data and grass samples collected from a large range of permanent grasslands in France, two models were built to explore grassland productivity and quality. In the first, the predictor variables were grass species functional type**, the proportions of different plant families, and a range of climatic variables. In the second, grass species functional type was replaced by two proxy variables***: forage dry matter content and the mean stage of plant phenological development.

Data were obtained from 190 permanent grasslands that were studied over two years at four periods of the year (i.e., at the beginning and end of the spring and during regrowth in the summer and autumn). The analyses revealed that climate plays an important role, especially in explaining grassland production and quality during periods of regrowth in the summer and autumn.

The taxonomic composition of the plant community (family level), the mean stage of plant phenological development, and forage dry matter content helped explain biomass production and forage quality across the board during the different seasonal periods.

Reliably estimating permanent grassland productivity

In the permanent grasslands studied, vegetative characteristics and climatic variables explained around 50% of the variability in forage nutritional value and 20 to 40% of the variability in biomass production. The two models were found to be essentially equivalent because they yielded very similar results. This finding shows that simple vegetative characteristics can be used to reliably approximate the complex effects of plant diversity on productivity in permanent grasslands. Based on these results and after incorporating data on the relationship between plant community composition and certain environmental services, a classification system for permanent grasslands in France was developed and published in collaboration with the French Livestock Institute.

Helping to evaluate ecosystem services

These findings have been useful in the development of predictive models examining biomass production and forage nutritional value in permanent grasslands. Such models are handy when seeking to assess the ecosystem services provided by grasslands at different scales, from livestock systems to geographical regions.

 

*Phenology is the study of cycles (most often annual) of natural phenomena in the living world that are influenced by seasonal variation in climatic conditions.

**This classification system assigns grasses to one of six functional types based on their growth strategies (resource capture or retention), their phenological developmental stage (early or late), their ability to accumulate biomass, their frequency of use, and their nutritional value.

***Variables that approximate or can act as substitutes for other variables

Contact(s)
Scientific contact(s):

Associated Division(s):
Animal Physiology and Livestock Systems
Associated Centre(s):
Auvergne-Rhône-Alpes

References

Michaud A., Plantureux S., Pottier E. & Baumont R., 2015. Links between functional composition, biomass production and forage quality in permanent grasslands over a broad gradient of conditions. Journal of Agricultural Science, 153, 891-906. DOI: 10.1017/S0021859614000653
Rossignol, N., Andueza, D., Carrère, P., Cruz, P., Duru, M., Fiorelli, J.-L., Michaud, A., Plantureux, S., Pottier, E. & Baumont, R., 2013. Assessing population maturity of three perennial grass species: influence of phenology and tiller demography along latitudinal and altitudinal gradients. Grass and Forage Science DOI: 10.1111/gfs.12067.
Michaud, A., Andueza, D., Picard, F., Plantureux, S. & Baumont, R., 2012a. The seasonal dynamics of biomass production and herbage quality of three grasslands with contrasting functional compositions. Grass and Forage Science 67, 64–76.
Michaud, A., Plantureux, S., Amiaud, B., Carrère, P., Cruz, P., Duru, M., Dury, B., Farruggia, A., Fiorelli, J. L., Kerneis, E. & Baumont, R., 2012b. Environmental factors influencing the botanical and functional composition of permanent grasslands. Journal of Agricultural Science, Cambridge 150, 219–236.
Launay F., Baumont R., Plantureux S., Farrie J-P., Michaud A. et Pottier E., 2011. Prairies Permanentes : des références pour valoriser leur diversité. Ed. Institut de l’Elevage. 128 pages.
Duru, M., Cruz, P. & Theau, J.P., 2010. A simplified method for characterizing agronomic services provided by species-rich grasslands. Crop & Pasture Science, 61, 420-433.