Understanding the resilience of Amazon floodplain forests
Funding: European Commission Individual Fellowship (grant no. 746181), National Geographic Explorer Grant (grant no. 165R-18), WGS Talent Postdoc Fellowship.
​
Main collaborators: Milena Holmgren (Wageningen University (WUR), the Netherlands), Arnold Lugo (WUR, Instituto Nacional de Pesquisas da Amazônia (INPA)), Jansen Zuanon (INPA), Bernardo Flores (Universidade Estadual de Campinas, Brazil), and Florian Wittmann (Karlsruhe Institute for Technology, Germany).
​
​
Climate warming is increasing the frequency and severity of droughts and fires in most of the Amazon basin. Although submerged during the wet season, Amazonian black-water floodplain forests, are highly susceptible to burn during drought years. After burning, they poorly regenerate, and with repeated fires can transition to a savanna-like state in which the forest appears unable to regenerate altogether (Flores et al. 2016, 2017). Why this collapse occurs is unknown. Previous research suggests that seed dispersal limitations may play a fundamental role in understanding the resilience of floodplain forests to fire perturbations. Fire destroys the seed bank completely, and the input of new tree seeds during the high-water season might be a crucial bottleneck for the regeneration of floodplain forests. In particular, the ability of tree seeds to reach ‘collapsed’ floodplain areas might depend on whether or not fish still exploit these areas. Amazonian fishes heavily consume fruits and seeds during the flood season and may
Catoprion mento
play a pivotal role in the successful dispersal of floodplain trees. As Amazonian fishes depend almost exclusively on the floodplain forests for food, the collapse of these forests will have dramatic consequences for fish communities, possibly creating a feedback loop that contributes to the sparse tree-cover state of burned floodplains. In this research project, we are investigating the ecological barriers that explain arrested regeneration of Amazonian floodplain forests after recurrent fire by evaluating the pathways of seed dispersal and the effects of fire on the composition and abundance of fish and tree communities.
Applying tree-ring techniques to growth rings in the ear bones (otoliths) of fish
Main collaborator: Bryan Black (Laboratory of Tree-Ring Research, University of Arizona)
This includes a variety of ongoing projects in which techniques originally developed to analyze growth rings in trees are used to analyze the growth rings formed in the ear stone, or otolith, of fish. Even more so than in terrestrial environments, determining the effects of global change in marine environments is hindered by a lack of long-term biological records. It is however, becoming increasingly clear that annual growth rings in fish bones, as well as bivalve shells and coral skeletons can provide exactly dated time series that span multiple decades, and in some instances, even centuries (e.g. van der Sleen et al. Climate Research 71). Given their accuracy, these growth increment chronologies can be directly integrated with instrumental climate records and so identify key climate variables associated with biological function, benchmark pre-industrial conditions, and allow assessing the effects of climate change in marine systems.
Is there a global signature of biological change in marine hotspots?
Main collaborators: John Morrongiello (School of BioSciences, The University of Melbourne) and Bryan Black (Laboratory of Tree-Ring Research, University of Arizona)
The world’s oceans are changing at an unprecedented rate due to climate change. In turn, a growing number of studies have identified the signature of oceanic warming in marine life through shifts in species distributions, abundances, and phenology (Poloczanska et al. 2013). But not all the world’s oceans are warming at the same rate: it is likely that the degree of biological sensitivity to environmental change is dependent on the rate of change itself. A recent study by Hobday and Pecl (2014) identified ~24 areas globally where the rate of warming is 90% faster than the rest of the oceans. Termed ‘global marine hotspots’, it is expected that there will be an intensification of biological response (either positive or negative) within these areas compared to neighbouring waters. In this project (led by John Morrongiello), we are preforming a global analysis of long-term trends in biological response to ocean warming inside and outside marine hotspots.