It’s time for the third edition of the EGU’s Twitter Journal Club, our interactive online discussion about a timely scientific article. If you have not yet taken part in one of these discussions, read more about it in our introductory post and make sure to participate on this third edition!
This time, we will be discussing an article recently published in the EGU’s Open Access journal Biogeosciences that features an innovative way of calculating the amount of carbon stored in tropical forests which incorporates tree-height data. The discussion will take place on Twitter next Thursday 27 September at 17:00 CEST, and you can take part by following the EGU’s Twitter account (@EuroGeosciences) and using the hashtag #egutjc3 on your tweets. Please email the EGU’s Science Communications Fellow Edvard Glücksman if you have any further questions.
Happy reading – and don’t be scared of the equations, they won’t bite!
Incorporating tree-height data into calculations of the amount of carbon stored in tropical forests reduces the estimates by roughly 13%. (Source: Imaggeo.net, credit: Alina Mihaela Luchian)
Tree height integrated into pantropical forest biomass estimates
Biogeosciences, 9, 3381–3403, 2012
Abstract. Aboveground tropical tree biomass and carbon storage estimates commonly ignore tree height (H). We estimate the effect of incorporating H on tropics-wide forest biomass estimates in 327 plots across four continents using 42 656 H and diameter measurements and harvested trees from 20 sites to answer the following questions:
1. What is the best H-model form and geographic unit to include in biomass models to minimise site-level uncertainty in estimates of destructive biomass?
2. To what extent does including H estimates derived in (1) reduce uncertainty in biomass estimates across all 327 plots?
3. What effect does accounting for H have on plot- and continental-scale forest biomass estimates?
The mean relative error in biomass estimates of destructively harvested trees when including H (mean 0.06), was half that when excluding H (mean 0.13). Power- and Weibull-H models provided the greatest reduction in uncertainty, with regional Weibull-H models preferred because they reduce uncertainty in smaller-diameter classes (< or = to 40 cm D) that store about one-third of biomass per hectare in most forests. Propagating the relationships from destructively harvested tree biomass to each of the 327 plots from across the tropics shows that including H reduces errors from 41.8 Mg/ha (range 6.6 to 112.4) to 8.0 Mg/ha (−2.5 to 23.0). For all plots, aboveground live biomass was −52.2 Mg/ha (−82.0 to −20.3 bootstrapped 95% CI), or 13%, lower when including H estimates, with the greatest relative reductions in estimated biomass in forests of the Brazilian Shield, east Africa, and Australia, and relatively little change in the Guiana Shield, central Africa and southeast Asia. Appreciably different stand structure was observed among regions across the tropical continents, with some storing significantly more biomass in small diameter stems, which affects selection of the best height models to reduce uncertainty and biomass reductions due to H. After accounting for variation in H, total biomass per hectare is greatest in Australia, the Guiana Shield, Asia, central and east Africa, and lowest in east-central Amazonia, W. Africa, W. Amazonia, and the Brazilian Shield (descending order). Thus, if tropical forests span 1668 million km2 and store 285 Pg C (estimate including H), then applying our regional relationships implies that carbon storage is overestimated by 35 PgC (31–39 bootstrapped 95% CI) if H is ignored, assuming that the sampled plots are an unbiased statistical representation of all tropical forest in terms of biomass and height factors. Our results show that tree H is an important allometric factor that needs to be included in future forest biomass estimates to reduce error in estimates of tropical carbon stocks and emissions due to deforestation.
Questions to think about:
1. How would you summarise this article in a tweet?
2. What are the broader implications of this study? (hint: see recent Nature blurb linked to below)
3. What methods could be used to improve data within biomass maps?
4. What are the practical implications of this and similar studies on how we interpret carbon storage within biomass?
5. Could this article be improved – specifically, are there too many equations?
Related media coverage:
The European Geosciences Union, through publishing house Copernicus Publications, publishes 14 peer-reviewed Open Access journals. Biogeosciences (BG, IF 3.859) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions.