We have created a video to promote the forthcoming conference
Megafauna and Ecosystem Function: from the Pleistocene to the Anthropocene, 18-20th March 2014
More details and registration information at the Conference Website
Mapping forest structure with airborne lidar: landscape-scale changes in forest structure and functional traits along an Andes-to-Amazon elevation gradient
We have a new paper, led by Greg Asner and his team at the Carnegie Airborne Observatory, which uses airborne lidar to understand how forest structure varies along our elevation transect in Peru. The plane flow over our plots in 2011, and gave unprecedented understanding of the differences in structure between lowland Amazonian and montane Andean forests. A wonderful demonstration of how new technologies (and some bold flying) can yield insights at large scale into some classic questions in ecology.
Asner, G. P., Anderson, C. B., Martin, R. E., Knapp, D. E., Tupayachi, R., Sinca, F., and Malhi, Y.: Landscape-scale changes in forest structure and functional traits along an Andes-to-Amazon elevation gradient, Biogeosciences, 11, 843-856, doi:10.5194/bg-11-843-2014, 2014.
Abstract. Elevation gradients provide opportunities to explore environmental controls on forest structure and functioning. We used airborne imaging spectroscopy and lidar (light detection and ranging) to quantify changes in three-dimensional forest structure and canopy functional traits in twenty 25 ha landscapes distributed along a 3300 m elevation gradient from lowland Amazonia to treeline in the Peruvian Andes. Elevation was positively correlated with lidar-estimated canopy gap density and understory vegetation cover, and negatively related to canopy height and the vertical partitioning of vegetation in canopies. Increases in canopy gap density were tightly linked to increases in understory plant cover, and larger gaps (20–200 m2) produced 25–30 times the response in understory cover than did smaller gaps (< 5 m2). Vegetation NDVI and photosynthetic fractional cover decreased, while exposed non-photosynthetic vegetation and bare soil increased, with elevation. Scaling of gap size to gap frequency (λ) was, however, nearly constant along the elevation gradient. When combined with other canopy structural and functional trait information, this suggests near-constant canopy turnover rates from the lowlands to treeline, which occurs independent of decreasing biomass or productivity with increasing elevation. Our results provide the first landscape-scale quantification of forest structure and canopy functional traits with changing elevation, thereby improving our understanding of disturbance, demography and ecosystem processes in the Andes-to-Amazon corridor.
The coffee forests of Ethiopia
I have just returned from the launch of our new project in Ethiopia. It is called ECOLIMITS, and is funded by the Department for International Development (DFiD) and the Natural Environment Research Council, NERC under the ESPA (Ecosystem Services and Poverty Alleviation) programme. The project examines the the interactions and thresholds of ecosystem services, poverty and human use of forest landscapes, looking at the cocoa producing landscapes of Ghana and the coffee landscapes of Ethiopia.
The project kick-off was in Addis Ababa, Ethiopia in Feb 2014, and was followed by a field visit to our research site in the Yayu Biosphere Reserve in SW Ethiopia, a long 15 hour drive from Addis, through the stunning landscapes of rural Ethiopia. Ethiopia has some stunning rainforests in its southern region (Oromia), and Arabica coffee originates in this region as a shrub that grows in the understorey of the rainforest. It was first cultivated by Ethiopians around a thousand years ago, and from there coffee culture spread to Yemen and Arabia (hence the name Arabica) and then on to western Europe and eventually around the world.
Montane forest root growth and soil organic layer depth as potential factors stabilizing Cenozoic global change
We have a new paper in Geophysical Research Letters, led by Chris Doughty, which uses data and insights from our Andean transect to come up with a new theory and model of how tree roots in tropical mountains have helped stabilise the Earth's climate. This is the first time we have linked out contemporary ecological studies with long-term geological and biosphere process - a product of a nice collaboration with Lyla Taylor and David Beerling at Sheffield University which originated from an informal chat with David Beerling at a conference. A nice example of how research can spin off in unexpected directions.
In a warmer world, tree roots are more likely to grow into the mineral layer of the soil, breaking down rock which will eventually combine with carbon dioxide. This weathering draws carbon dioxide out of the atmosphere and cools the planet. This theory suggests that mountainous ecosystems have acted like the Earth's thermostat, addressing the risk of 'catastrophic' overheating or cooling over millions of years. However these processes act too slowly to have any influence on contemporary global warming.
Doughty, C. E., L. L. Taylor, C. A. J. Girardin, Y. Malhi, and D. J. Beerling (2014), Cenozoic global change possibly stabilized by montane forest root growth and soil organic layer depth, Geophys. Res. Lett., 41, doi:10.1002/2013GL058737.
The story is covered in the Mail Online here: Tree roots act as 'Earth's thermostat': Mountain forest growth has stabilised the Earth's climate for millions of years
Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements - paper in Nature
We have a paper in Nature this week (it makes the cover of Nature) that answers a long-standing question about the net carbon balance of the Amazon forest. It uses aircraft flights throughout the year at four different locations to measure the change in carbon dioxide concentration if air as it passes over the Amazon Basin. The study shows that in wet years and wet seasons the Amazon is a net sink (i.e. absorbs carbon) from the atmosphere, but in dry years and dry seasons it is carbon neutral or a source of carbon. Our main contribution in Oxford was to provide analyses and insight from our RAINFOR-GEM intensive monitoring plots across Amazonia, which suggest that the loss of the carbon sink was caused by a reduction in photosynthesis.
Gatti L.V., M. Gloor, J. B. Miller, C. E. Doughty, Y. Malhi, L. G. Domingues, L. S. Basso, A. Martinewski, C. S. C. Correia, V. F. Borges, S. Freitas, R. Braz, L. O. Anderson, H. Rocha, J. Grace, O. L. Phillips & J. Lloyd Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements, Nature 506, 76–80.
Oxford has one of the longest weather records in the world, stretching back to the 1760s at the Radcliffe Meteorological Station. This January has been the wettest winter month ever recorded (winter months = December, January, February), with rainfall almost three times the average.
The result is floodplains that have become vast lakes, as seen in these photos of Port Meadow during my morning run/wade. Port Meadow tends to flood in most wet spells, but I have never seen it so awash with water.
Some wonderful photos here, all taken by Topher Bentley, of the landscapes and moods of the Andes transect during our field campaign last year.
Yadvinder Malhi is an ecosytem ecologist and Professor of Ecosystem Science at Oxford University