Detecting the response of plant functional traits to nutrient status in grassland by spectral reflectance measurements

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The challenge of present grassland research is to better understand the impact of environmental conditions and management on sward properties and productivity and, at the same time, to consider the impact of production on the ecosystem. Hence, knowledge is required to understand how managed grassland communities respond to manipulation by humans and animals and how this response can be detected non-destructively. In mixed grassland swards, the response of plants to manipulation can be interpreted by a new approach that is based on the expression of functional traits, often irrespective of floristic composition. It is known that traits affect spectral properties as measured above the canopy. The objective of the project is to learn how spectral reflectance signatures must be interpreted to identify functional traits of grassland communities along a gradient of soil nutrient content. Throughout two years, optical properties of canopy in the Rengen Grassland Experiment (since 1941) will be measured with a crane mounted high resolution spectrometer. Sophisticated spectral analyses will be applied to derive functional relations between spectral response and plant traits as affected by soil nutrient status. In the second and third year, the derived mathematical model describing the relationship between community functional traits and spectral reflectance will be validated on grassland fields elsewhere in Germany.