Analysis of some direct and indirect methods for estimating root biomass and production of forests at an ecosystem level

Abstract

The relationship of global climate change to plant growth and the role of forests as sites of carbon sequestration have encouraged refinement of the estimates of root biomass, and production has been highlighted. However, tremendous controversy exists in the literature as to which is the best method to determine fine root biomass and production. This lack of consensus makes it difficult for researchers to determine which methods are most appropriate for their system. The sequential root coring method was the most commonly used method to collect root biomass data in the past and is still commonly used. But within the last decade the use of rninirhizotrons has become a favourite method of many researchers. In addition, due to the high labour-intensive requirements of many of the direct approaches to determine root biomass, there has been a shift to develop indirect methods that would allow fine root biomass and production to be predicted using data on easily monitored variables that are highly correlated to root dynamics. Discussions occur as to which method should be used but without gathering data from the same site using different methods, these discussions can be futile. This paper discusses and compares the results of the most commonly used direct and indirect methods of deterrnining root biomass and production: Sequential root coring, ingrowth cores, rninirhizotrons, carbon fluxes approach, nitrogen budget approach and correlation's with abiotic resources. No consistent relationships were apparent when comparing several sites where at least one indirect and one direct method were used on the same site. Until the different root methods can be compared to some independently derived root biomass value obtained from total carbon budgets for systems, one root method cannot stated be the best and the method of choice will be determined from a researcher's personal reference, experiences, equipment, and/or finances.