A neat new 3D scan of an oak at Wytham Woods by Mat Disney's team from UCL. The team scanning all of our 18 ha ForestGeo research plot, where we are tracking 20,000 trees. We are increasingly interested in extracting information on tree form, mechanics and function from these images
A report on our Wytham plot is available here.
And below is a nice video explaining how information on tree structure can be extracted from these scans.
The RAINFOR consortium had a paper in Nature last week, describing the declining in the Amazon biomass carbon sink. This result is based on decades of monitoring of forest sample plots across Amazonia (particularly since the 1990s), and provides the only medium-term ground observational evidence for a carbon sink in tropical forests. Our previous work has shown the evidence for a carbon sink in Amazonian biomass (Phillips et al 1998, Science), and evidence that it briefly shut off after the 2005 drought (Phillips et al 2009, Science). The new study shows evidence of a gradual multi-decadal decline, apparently because growth stimulation has flattened out, but tree mortality rates are increasing gradually over time. The gradual nature of the increase in mortality suggests it is not driven by specific drought events, but reflects a general shortening of tree life times. On this trend the Amazon biomass carbon sink can be expected to disappear in about a decade.
The paper can be accessed here...
Brienen R.J.W. et al. (2015) Long-term decline of the Amazon carbon sink, Nature 519, 344–348. doi:10.1038/nature14283
The linkages between photosynthesis, productivity, growth and biomass in lowland Amazonian forests
We have a new paper out in Global Change Biology, the first spatial comparison of productivity and carbon cycling from our GEM plots in lowland Amazonia. The plots spread across five sites in Peru, Bolivia and Brazil, spanning gradients from wet to dry, and from infertile soils in eastern Amazonia to moderately fertile soils in western Amazonia.
The GEM approach gives us insights into the full carbon budget of forests, from total photosynthesis or GPP, through its allocation to NPP or plant respiration, through the allocation of NPP to canopy, wood or fine roots, and through to biomass stocks and mortality rates. In this paper we explore to what extent these processes are simply related to each other. Can growth rates of a forest be predicted from photosynthesis rates, can biomass be predicted from growth rates?
We show that there is little simple linkage between growth and photosynthesis, because shifts in carbon use efficiencieny (the fraction of photosynthesis used for biomass growth) and the allocation of NPP matter. There is also no simple linkage between growth rates and biomass - in mature forests in Amazonia the spatial patterns in biomass are determined more by the spatial variation in tree biomass residence times (or mortality rates) matters more than variation in production. To predict biomass, we need to understand why trees die more than how trees grow. This unfortunately is a much harder challenge.
The paper represents a huge effort by GEM field teams in all three countries, who spent many weeks per month over four years collecting and processing data (and continue to do so). It was supported by the Gordon and Betty Moore Foundation, and also the EU project GEOCARBON. The paper can be accessed below.
Malhi Y., C. E. Doughty, G. R. Goldsmith, D. B. Metcalfe, C. A. J. Girardin, T. R. Marthews, J. del Aguila-Pasquel3, L. E. O. C. Aragão, A. Araujo-Murakami, P. Brando, A. C. L. da Costa, J. E. Silva-Espejo, F. Farfán Amézquita, D. R. Galbraith, C. A. Quesada, W. Rocha, N. Salinas-Revilla, D. Silvério, P. Meir and O. L. Phillips (2015) The linkages between photosynthesis, productivity, growth and biomass in lowland Amazonian forests. Global Change Biology, DOI: 10.1111/gcb.12859. Supplementary Information.
For a few days we visited the Chiquibul forest nestled in the Maya Mountains, a biodiversity hotspot in Central America. This forest is a spectacular wilderness, breathtaking for a small country such as Belize, and packed with Mayan ruins. We stayed at the Las Cuevas Research Station.
I have just returned from a visit our new project in Belize, SUSFOR. The project is funded by the Darwin Fund and is aimed at building forest monitoring capacity in Belize. I was hosted by Percy Cho, who is with the Belize Forestry Department and also a postdoc at Oxford with me for this project.
Over our visit we spanned the length and breadth of this small but astonishingly varied country, from wet rainforest to pine savanna, from smallholder farms to vast agroindustrial clearings to breathtaking wilderness.
Three things are particularly fascinating to me about Belize's forests: (1) the frequency of hurricane damage; (2) the widespread limestone bedrock leading to non-acidic tropical soils and (3) the extensive past legacy of the Mayan civilization.
The hurricane damage can be spectacular even decades after the event, as if a giant invisible hand has snapped off the tree crowns, which for many trees have resprouted in twisted and eccentric forms.
Photosynthetic seasonality of global tropical forests constrained by hydroclimate
There is a new paper in Nature Geoscience that gives a unifying and elegant insight into how rainfall seasonality controls the seasonality of photosynthesis across the tropics
Guan, K., Pan M., Li H., Wolf A., Wu J., Medvigy D., Caylor K.K., Sheffield J., Wood E.F., Malhi Y., Liang M., Kimball J.S., Saleska S., Berry J., Joiner J., Lyapustin A.I., Photosynthetic seasonality of global tropical forests constrained by hydroclimate, Nature Geoscience, early online, DOI:10.1038/ngeo2382
We have just an intensive workshop of our CHAMBASA project, a busy but productive week focussed on really getting to grips with the data we had collected in Peru in 2013 , looking at the relationships between leaf properties, forest plot properties and landscapes along our transect in Peru, combining field data, theory and aircraft to tackle this question. Guests from far way included Brian Enquist from Arizona, and Greg Asner and Robin Martin from California. A real highlight was the inauguration and revelation of our database, which has been a huge amount of work.
Looking ahead, we have a follow-up in Hawaii in July, on a path to produce a special issue of papers later in the year.
We have a new paper in Nature this week (led by Chris Doughty) which demonstrates the carbon cycle influence of the 2010 Amazon drought through close monitoring of our intensive carbon cycle plots. It demonstrates the power of the intensive monitoring approach we have developed through the GEM network.
The paper is available here.
Doughty, C.E., Metcalfe, D.B., Girardin, C.A.J., Farfan Amezquita, F., Galiano Cabrera, D., Huaraca Huasco, W., Silva-Espejo, J.E., Araujo-Murakami, A., da Costa, M.C., Rocha, W., Feldpausch, T.R., Mendoza, A.L.M., da Costa, A.C.L., Meir, P., Phillips, O.L. and Malhi, Y. (2015) Drought impact on forest carbon dynamics and fluxes in Amazonia. Nature, 519: 78-82.
Yadvinder Malhi is an ecosytem ecologist and Professor of Ecosystem Science at Oxford University