Critical analysis of root : shoot ratios in terrestrial biomes

Abstract

One of the most common descriptors of the relationship between root and shoot biomass is the root : shoot ratio, which has become a core method for estimating root biomass from the more easily measured shoot biomass. Previous reviews have examined root : shoot ratio data, but have only considered particular vegetation types and have not always critically reviewed the data used. Reliable root : shoot ratios are needed for a wide range of vegetation types in order to improve the accuracy of root biomass estimates, including those required for estimating the effects of land management and land use change in National Greenhouse Gas Inventories.This study reviewed root : shoot ratios in terrestrial biomes. A key facet of our analysis was a critical methodological review, through which unreliable data were identified and omitted on the basis of specific criteria. Of the 786 root : shoot ratio observations collated, 62% were omitted because of inadequate or unverifiable root sampling methods. When only the reliable data were examined, root : shoot ratios were found to be negatively related to shoot biomass, mean annual precipitation, mean annual temperature, forest stand age, and forest stand height.Although a single allometric equation derived in this study reliably predicted root biomass from shoot biomass for forests and woodlands, in general, the use of vegetationspecific root : shoot ratios were found to be a more accurate method for predicting root biomass. When the root : shoot ratio data collated here were applied to an analysis of the global carbon budget, there was a 50% increase in estimated global root carbon stock, and a 12% increase in estimated total carbon stock of terrestrial vegetation. The use of the vegetation-specific root : shoot ratios presented in this study is likely to substantially improve the accuracy of root biomass estimates for purposes such as carbon accounting and for studies of ecosystem dynamics.

Soil properties and species composition under different grazing intensity in an alpine meadow on the eastern Tibetan Plateau, China

“…Aboveground and belowground biomass are different forms to fulfill the plant function as a whole (Mokany et al 2006), which make aboveground and belowground biomass allocation a central issue in plant ecology (Yang et al 2009). Former researchers used the R/S ratio to gain a greater understanding of the relationship between aboveground and belowground biomass.…”

“…Former researchers used the R/S ratio to gain a greater understanding of the relationship between aboveground and belowground biomass. The R/S ratio is an index for the differential investment of plant photosynthates between the aboveground and belowground, a complicated process which is the cumulative response of vegetation to biotic, abiotic, and management influences (Mokany et al 2006). In order to adapt to the changing environment conditions, the R/S ratio of plants is often modified to maximize the ability to capture resources (Deng et al 2014a).…”

An overview of existing and promising technologies for national forest monitoring

“…Belowground forest components are often overlooked in forest resource assessments while they constitute a significant source of uncertainty in the global carbon stock (Mokany et al 2006). Belowground biomass is indeed one of the most difficult field variables to measure, particularly for destructive measurements (Picard et al 2012).…”

“…Belowground woody biomass or volume is often an overlooked component in forest assessment, despite its fundamental variation across biomes and forest types (Mokany et al 2006). Ground Penetrating Radar (GPR) is a nondestructive geophysical technique widely used in locating underground objects (e.g., restrictive soil horizons, stone lines, bedrock, water tables, buried artifacts, pipes, and cables).…”

Estimation of Forest Carbon Densities Using Sample Plots for Development of Forest Reference Level in Vietnam

“…In this work, the values proposed by Mokany et al (2006) for R, which is 0.205 for SSPs with tAGB/ha < 125 ton/ha or 0.235 for SSPs with tAGB/ha ≥ 125 ton/ha, are applied.…”