Allometry for Biomass Estimation in Jatropha Trees Planted as Boundary Hedge in Farmers’ Fields

Abstract

Regrowth and planted trees in agricultural landscapes are rarely protected from clearing under national Forest Acts. There is, therefore, some question over the long-term security of any value they might provide to biodiversity and the global carbon cycle. Engaging landholders in carbon credits that are conditioned on planted areas being maintained into the future could improve the situation. To begin carbon trading, landholders need precise and accurate estimates of the carbon sequestered by the trees in their fields. Accurate estimates of carbon stocks depend to a greater degree on the availability and adequacy of the allometric equations that are used to estimate tree biomass. The present study has developed an allometric model for estimating the woody biomass of Jatropha trees planted as boundary hedges in agricultural landscapes under smallholder farming systems in Malawi. The predictive performance of the model was assessed and was subsequently compared with the published Jatropha models. The results showed that the statistical fits of our model were generally good, enabling one to use it with confidence for estimating wood biomass in Jatropha stands from which they were derived. The published Jatropha models consistently overestimated the woody biomass by as much as 55%, rendering them unsuitable for application in estimating woody biomass in our study sites.

Tree or shrub: a functional branch analysis of Jatropha curcas L.

“…Achten et al (2010), the first equation of Makungwa et al (2013) and Firdaus and Husni (2012) share similar patterns with the highest aboveground biomass estimations, whereas Ghezehei et al (2009) and juvenile stage of Baumert and Khamzina (2015) share the lowest aboveground biomass estimations. The second equation of Makungwa et al (2013), jatropha FBA, adult and mature stage of Baumert and Khamzina (2015) are situated in the middle of previous two patterns. The grouping pattern for increasing biomass with increasing diameter is likely due to similarities in age.…”

“…3 Comparison of predicted and measured aboveground tree biomass components: a measured total biomass, b measured branch biomass, c measured twig and leaf biomass and for belowground d measured total proximal root biomass using stem diameter to estimate aboveground biomass based on data obtained from 41 jatropha seedlings (up to 3 cm stem diameter), while Ghezehei et al (2009) used stem base diameter and other predictors to develop allometric equations for aboveground biomass estimation using 12 samples aged 16-24-monthold. Makungwa et al (2013) developed two aboveground biomass allometric equations based on stem diameter measured at 10 cm aboveground from 172 and 442 samples of one to three-year-old jatropha planted as smallholder crop boundary hedges, in five different regions. Firdaus and Husni (2012) determined allometric equations for aboveground and belowground biomass using stem diameter from 15 sampling of 6-46-month-old jatropha.…”

“…The grouping pattern for increasing biomass with increasing diameter is likely due to similarities in age. Moreover variations in jatropha biomass across different sources derived from empirical allometric and jatropha FBA can be caused by differences in planting material, site characteristics such as soil, vegetation and over-storey structure (MacFarlane et al 2014), or in silvicultural practices and development stage or age at the time data were collected (Ghezehei et al 2009;Makungwa et al 2013). As further explored in ongoing research for allometric equations of other species (Harja, pers.…”

“…Jatropha allometric research historically used empirical models and destructive sampling to determine aboveground biomass (Ghezehei et al 2009;Achten et al 2010;Makungwa et al 2013), with limited belowground data (Firdaus and Husni 2012;Baumert and Khamzina 2015). However, there are no data available for biomass partitioning in the generative stage (harvest index).…”

Biomass, Carbon and Nutrient Storage in a 30-Year-Old Chinese Cork Oak (Quercus Variabilis) Forest on the South Slope of the Qinling Mountains, China

“…However, there was no significant difference in tree components biomass estimation, with the exception of roots, among all the available allometric equations. In some cases the power function failed, and then transformed models were needed to develop significant allometric equations for different tree species, locations, and specific-components [7,25,27,28,[42][43][44][45][46][47].…”