Social and Behavioral Sciences Commons^™

Randomization Tests For Quantifying Species Importance To Ecosystem Function, Nicholas J. Gotelli, Werner Ulrich, Fernando T. Maestre

College of Arts and Sciences Faculty Publications

1. Quantifying the contribution of different species to ecosystem function is an important challenge. We introduce simple randomization tests (and software) for quantifying the average effect of species on ecosystem variables measured in multiple plots with and without the presence of a particular species. These randomization tests formalize the analysis of uncontrolled 'natural experiments' and quantify species effects in standardized deviation units. 2.We tested the method with data on ecosystem function in biological soil crust assemblages of lichens in semi-arid gypsum outcrops in central Spain. In sixty-three 50cm×50cm sample plots, we measured the presence and percentage cover of 17 species …