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.