Biases and Errors Associated with Different Root Production Methods and Their Effects on Field Estimates of Belowground Net Primary Production

Abstract

Many estimates of root production in the literature were based on sequential coring of biomass methods now considered unreliable. New methods such as minirhizotron and isotope labeling were developed to overcome known biases of old methods, but also have different assumptions and biases that can have large effects on estimates. Variations on the old root ingrowth method are now widely used because it is easy, straightforward, and does not require expensive specialized materials. Only recently have there been sufficient studies of new methods to better define the importance of various potential biases and to compare among ingrowth, minirhizotron, and isotope labeling studies. How these three methods are executed in the field and/or in how data are used to calculate root production can have large effects on mitigating some of the potential biases of each of these methods. There are three main objectives of this chapter. First, known biases of each method are described and suggestions of procedures that reduce problems leading to over-and underestimation of absolute values of root production are made. Second, a comparative approach of methods is taken to assess the importance of biases, because the correct absolute answer is never known. Third, how method biases may manifest differently in annual, short-lived perennial, and long-lived perennial plant root systems are assessed. Comments on root biomass separation from soil and how this affects estimates of root production are also made, because all three methods rely either directly or indirectly on this procedure to derive an estimate of root production.

Proportion of Root Production in Several Temperate Grasslands of Central Europe

“…In order to assess yearly root increments (root production), the in-growth core technique (Milchunas, 2012) was used in all sites (see Fiala, 1998Fiala, , 2000Fiala, , 2001Fiala et al, 2009Fiala et al, , 2012Holub et al, 2013a, b;Tomaškin, Tomaškinová, 2012). The same method used in all sites enables us to compare reliably summarised data.…”

Root inclusion net method: novel approach to determine fine root production and turnover in Larix principis-rupprechtii Mayr plantation in North China

“…Two of the most commonly used methods that determine the fine root production are the in-growth core method and minirhizotrons method (Majdi et al, 2005;Milchunas, 2012). Both have drawbacks that influence the reliability of the observations, mostly related to the fact that a certain degree of soil environment disturbance is unavoidable before commencing the measurement.…”

Root growth of maize as studied with minirhizotrons and monolith methods

“…Discrepancies in root quantity data have been reported by other researchers using similar methods. This could be attributable to the experimental conditions, the method for installing the minirhizotron, and the root parameter used in the comparisons (Upchurch & Ritchie 1983;McMichael & Taylor 1987;Jose et al 2001;Bernier & Robitaille 2004;Milchunas 2012;Vamerali et al 2012;Taylor et al 2014). Furthermore, a high correlation of RLD between MT and QMM meant that MT was a reliable method, and the fact that the correlation was lower using the number of roots from MT has important implications on root parameters measured using MT.…”

“…Some indices of biomass, production, turnover, and longevity of fine roots have been constructed using MT (Smucker et al 1982(Smucker et al , 1987Cheng et al 1991;Bai et al 2005;Majdi et al 2005;Faget et al 2012;Vamerali et al 2012). Studies were conducted to compare MT with the soil-water-depletion, core, and monolith methods of quantifying plant root distribution (Majdi et al 1992;Heeraman & Juma 1993;Samson & Sinclair 1994;Kirkham et al 1998;Jose et al 2001;Liu et al 2009;Liao et al 2010;Milchunas 2012;Rytter & Rytter 2012;Taylor et al 2013;Liao et al 2014).…”