Testing the generality of above‐ground biomass allometry across plant functional types at the continent scale

Abstract

Accurate ground-based estimation of the carbon stored in terrestrial ecosystems is critical to quantifying the global carbon budget. Allometric models provide cost-effective methods for biomass prediction. But do such models vary with ecoregion or plant functional type? We compiled 15 054 measurements of individual tree or shrub biomass from across Australia to examine the generality of allometric models for above-ground biomass prediction. This provided a robust case study because Australia includes ecoregions ranging from arid shrublands to tropical rainforests, and has a rich history of biomass research, particularly in planted forests. Regardless of ecoregion, for five broad categories of plant functional type (shrubs; multistemmed trees; trees of the genus Eucalyptus and closely related genera; other trees of high wood density; and other trees of low wood density), relationships between biomass and stem diameter were generic. Simple power-law models explained 84-95% of the variation in biomass, with little improvement in model performance when other plant variables (height, bole wood density), or site characteristics (climate, age, management) were included. Predictions of stand-based biomass from allometric models of varying levels of generalization (species-specific, plant functional type) were validated using whole-plot harvest data from 17 contrasting stands (range: 9-356 Mg ha(-1) ). Losses in efficiency of prediction were <1% if generalized models were used in place of species-specific models. Furthermore, application of generalized multispecies models did not introduce significant bias in biomass prediction in 92% of the 53 species tested. Further, overall efficiency of stand-level biomass prediction was 99%, with a mean absolute prediction error of only 13%. Hence, for cost-effective prediction of biomass across a wide range of stands, we recommend use of generic allometric models based on plant functional types. Development of new species-specific models is only warranted when gains in accuracy of stand-based predictions are relatively high (e.g. high-value monocultures).

Developing allometric models to predict the individual aboveground biomass of shrubs worldwide

“…(b) Mean relative errors [Error = (AGB est − AGB obs /AGB obs ) × 100] for the compared models across the observed aboveground biomass values. The compared models correspond to Model 1 proposed here; the global model proposed by Chave et al (), including diameter at breast height (DBH), height ( H ) and wood density (ρ); the model proposed by Jucker et al () for angiosperms including mean crown diameter (CD) and H ; and the shrub models proposed by Paul et al () using stem diameter at 10 cm height (D10) as a main variable (MULTI and SHRUB models). RMSE = root mean square error; Bias = average relative systematic error of model predictions [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…with both 3a and 3b developed by Paul et al () based only upon stem diameter at 10 cm height (D10) at the Australian continental scale.…”

Height-diameter allometry and above ground biomass in tropical montane forests: Insights from the Albertine Rift in Africa

“…However, building height-diameter allometric models for different species is often challenging as a great number of stems per size-class is required. A recent study form Australia showed that using generic allometric models based on plant functional types rather than species-specific models [80]. Moreover, in montane forests, the same species can have different heights for a given diameter depending on exposure to wind, windward/leeward side of mountain, slope or other factors (soil) (see [81]).…”

Conversion of sub-tropical native vegetation to introduced conifer forest: Impacts on below-ground and above-ground carbon pools

“…The above-ground biomass was estimated using general allometric relationships for softwood plantations and eucalypt vegetation for the Pinus sp. forest and adjacent vegetation, respectively (Paul et al, 2016). These allometrics were developed based on existing biomass datasets in Australia and were based on 455 individuals of softwoods (mostly Pinus radiata) and 6004 eucalypt individuals (Eucalyptus and closely-related genus of Corymbia and Angophora).…”