We do not currently know of any antonyms for quadrat.
The noun quadrat is defined as:
An area of land, marked for studying its plants, animals, soil, natural processes, etc. While originally rectangular, modern quadrats can be rectangular, circular, irregular, etc. (e.g.: Krebs, C.J., 1999. Ecological Methodology. Addison-Welsey Educational Publishing, Inc., Menlo Park, California; Wheater, C.P., Bell, J.R., Cook, P.A., 2011. Practical Field Ecology: A Project Guide. John Wiley and Sons, Chichester, West Sussex, England.)
