Allometric equations for estimating biomass in agricultural landscapes: I. Aboveground biomass uri icon

abstract

  • Meeting the reducing emissions from deforestation and degradation (REDD) framework demands stringent carbon measuring, reporting and verifying methods. In most cases, estimates of aboveground carbon stocks rely on allometric equations. Although generic and species-specific allometries have been developed for conventional areas such as forests, their use in agricultural landscapes is questionable as agricultural trees are typically managed and rarely mono-specific. Therefore, there is a need to develop a robust generic allometry that accounts for the heterogeneity of tree diversity throughout the landscape. Allometric equations were developed from empirical destructive sampling of 72 trees (diameter at breast height (dbh): 3-102 cm) from three 100 km(2) benchmark sites in Western Kenya. Diameter at breast height alone provided reliable prediction for aboveground biomass (17 +/- 0.02 Mg C ha(-1)) with >95% accuracy. Published equations overestimated landscape biomass due to errors in either smaller trees (dbh <10 cm) which dominate the landscape (66%) or the few larger trees (dbh >40 cm) which constitute 3% of all the trees but hold most of the biomass (48%). The apparently small differences in the equations for small trees could add up to a large amount of carbon when looking at a landscape. This study recommends diameter as the basis for assessing tree biomass in Western Kenyan agricultural mosaics. The equations developed are a useful tool for assessing the potential for carbon sequestration in agricultural landscapes and represent key information for scaling biomass estimates for entire landscapes. (C) 2012 Elsevier B.V. All rights reserved.
  • The high heterogeneity and diverse management effects on trees in agricultural landscapes limit the use of standard allometric equations developed for forests; hence the need to develop robust allometric equations and root:shoot ratios (RS) for more accurate estimation of belowground biomass. Local generic equations were developed from 72 trees (diameter at breast height (dbh): 3-102 cm) destructively sampled across three 100 km(2) benchmark sites in Western Kenya. Belowground biomass of the harvested trees accounted for about 20% of the total tree biomass; yielding an overall RS of 0.26, which varied across an altitudinal and precipitation gradient. The equation based on dbh alone estimated belowground biomass carbon in agricultural mosaics of Western Kenya to be 5 +/- 0.01 Mg C ha(-1) with about 90% accuracy. Two of the equations recommended for tropical species produced estimates that were about 35 and 21% lower. The equation with dbh as predictor is therefore reliable for estimating belowground biomass in agricultural landscapes while RS should be used with great care depending on soil and management conditions as shown by the great variability among the blocks evaluated. Equations presented in this study will significantly improve the accuracy of root biomass estimates in agricultural landscape mosaics without the high investments in excavating the root system. (C) 2012 Elsevier B.V. All rights reserved.
  • The high heterogeneity and diverse management effects on trees in agricultural landscapes limit the use of standard allometric equations developed for forests; hence the need to develop robust allometric equations and root:shoot ratios (RS) for more accurate estimation of belowground biomass. Local generic equations were developed from 72 trees (diameter at breast height (dbh): 3â??102 cm) destructively sampled across three 100 km2 benchmark sites in Western Kenya. Belowground biomass of the harvested trees accounted for about 20% of the total tree biomass; yielding an overall RS of 0.26, which varied across an altitudinal and precipitation gradient. The equation based on dbh alone estimated belowground biomass carbon in agricultural mosaics of Western Kenya to be 5 ± 0.01 Mg C haâ??1 with about 90% accuracy. Two of the equations recommended for tropical species produced estimates that were about 35 and 21% lower. The equation with dbh as predictor is therefore reliable for estimating belowground biomass in agricultural landscapes while RS should be used with great care depending on soil and management conditions as shown by the great variability among the blocks evaluated. Equations presented in this study will significantly improve the accuracy of root biomass estimates in agricultural landscape mosaics without the high investments in excavating the root system

publication date

  • 2012
  • 2012
  • 2012
  • 2012