Testing the generality of below-ground biomass allometry across plant functional types

Abstract

Accurate quantification of below-ground biomass (BGB) of woody vegetation is critical to understanding ecosystem function and potential for climate change mitigation from sequestration of biomass carbon. We compiled 2 054 measurements of individual tree and shrub biomass from across a broad range of ecoregions (arid shrublands to tropical rainforests) to develop allometric models for prediction of BGB. We found that the relationship between BGB and stem diameter was generic, with a simple power-law model having a BGB prediction efficiency of 72-93% for four broad plant functional types: (i) shrubs and Acacia trees, (ii) multi-stemmed mallee eucalypts, (iii) other trees of relatively high wood density, and; (iv) a species of relatively low wood density, Pinus radiata. There was little improvement in accuracy of model prediction by including variables (e.g. climatic characteristics, stand age or management) in addition to stem diameter alone. We further assessed the generality of the plant functional type models across 11 contrasting stands where data from whole-plot excavation of BGB were available. The efficiency of model prediction of stand-based BGB was 93%, with a mean absolute prediction error of only 6.5%, and with no improvements in validation results when species-specific models were applied. Given the high prediction performance of the generalised models, we suggest that additional costs associated with the development of new species-specific models for estimating BGB are only warranted when gains in accuracy of stand-based predictions are justifiable, such as for a high-biomass stand comprising only one or two dominant species. However, generic models based on plant functional type should not be applied where stands are dominated by species that are unusual in their morphology and unlikely to conform to the generalised plant functional group models.

Tree size and climatic water deficit control root to shoot ratio in individual trees globally

“…This theory has been supported by recent research showing that the R : S of an individual plant is modulated by environmental factors (Poorter et al ., ; Fatichi et al ., ). However, understanding the mechanisms underpinning plant allocation and its response to environmental factors is an active field of research (Delpierre et al ., ; Paul et al ., ), and it is likely that plant size and species composition have an effect on R : S . Accounting for these sources of variation is an important challenge for modelling (Franklin et al ., ).…”

Separating Regressions for Model Fitting to Reduce the Uncertainty in Forest Volume-Biomass Relationship

“…In the bottom right part of each scatter plot, Bs and V have a significant linear relationship with all coefficients of determination greater than 0.6, although a few samples are located in the restricted zones for some species and forest types (No. 8,10,15,18,25,27,29,30). All regression curves (Bs-to-Bt) and lines (V-to-Bs) avoid falling in the "restricted zones."…”

“…Both analyses of the regression and simulation demonstrate that the wood density impacts the parameters more than the allometric relationship does. This paper presents an applicable method for testing the field data using reasonable wood densities, restricting the error in field data processing based on limited field plots, and achieving a better understanding of the uncertainty in building those equations.cannot be conducted directly [3,4] due to restrictions like heavy load of fieldwork [5,6], non-destructive measurement requirements [7], and difficulty of belowground biomass (BGB) measurement [8][9][10]. Indirect methods have been applied in estimating forest biomass through the amount of growing volume [11].…”

“…cannot be conducted directly [3,4] due to restrictions like heavy load of fieldwork [5,6], non-destructive measurement requirements [7], and difficulty of belowground biomass (BGB) measurement [8][9][10]. Indirect methods have been applied in estimating forest biomass through the amount of growing volume [11].…”

Stand Feature Associating With Climate Seasonality Determinate Root-Shoot Ratios of Forest Ecosystems in China

“…For example, natural forests generally featured with more species richness increase ecosystem carbon storage (Liu et al, 2018), while planted forests had higher productivity and thus higher carbon sequestration rates due to only highly productive species were planted (Guo and Ren, 2014). Root-shoot ratio, a key parameter to describe the biomass allocation between aboveground and belowground, provides a practical tool to estimate belowground biomass (BGB) by relatively easily measured aboveground biomass (AGB) (Marziliano et al, 2015;Mokany et al, 2006;Paul et al, 2019). It not only re ects a plant's speci c adaptive responses to its environment (Agathokleous et al, 2019), but also acts as a key descriptor for terrestrial ecosystem carbon modeling (Wang et al, 2008).…”