A comparison of methods for converting rhizotron root length measurements into estimates of root mass production per unit ground area

Abstract

Rhizotrons provide valuable information about plant root production, but measurements are usually made in units of root length per unit surface area of observation window surface. These measurement units are not easily comparable to above-ground plant growth. To address this deficiency, several techniques have been developed to convert rhizotron measurement units into root mass production per unit ground area. In this study, four different conversion methods were applied to the same dataset of rhizotron measurements. This data was used to reveal the effect of conversion method upon estimates of the temporal variation in, and annual magnitude of, gross root mass production. Application of four different conversion methods resulted in gross root production estimates ranging between 2.1 and 11.4 t ha−1 year−1. Temporal variation in gross root mass production also varied between methods. All current methods for quantifying root production are likely to cause some disturbance and bias. Based upon a comparison of the sources of error present in each conversion method, we assess which methods are likely to produce the most reliable estimates of root biomass production per unit ground area, and propose additional measurements which could further improve accuracy.