The measurement and quantification of generalized gradients of soil fertility relevant to plant community ecology
Daou, L.;Shipley, B.. 2019. Ecology 100:e02549
Abstract
We propose an operational definition of soil “fertility” that is applicable to plant community ecology and develop a method of measuring and quantifying it, using structural equations modeling, that is generalizable to soils in different regions whose fertility has different causes. To do this, we used structural equation modelling (SEM). The measurement submodel predicts the latent “generalized fertility”, FG, of a soil using four indicator variables: the relative growth rates of Festuca rubra, Trifolium pretense, Triticum aestivum and Arabidopsis thaliana. The direct causes of FG in this study were the supply rates of, P and K as well as three indirect causes consisting in three physical soil properties, but these can change between studies. The model was calibrated using 76 grassland soils from southern Quebec, Canada and independently tested using aboveground net primary productivity (NPP) of the natural vegetation over two growing seasons. Both the measurement submodel and the full SEM fit the data well. The FG values predicted 51% of the variance in NPP and was a better predictor than any other single variable, including the actual nutrient flux rates. Furthermore, this model can be applied to grassland soils anywhere because of its modular nature in which the causes and effects of soil fertility are clearly separated.
