Seasonal leaf dynamics in an Amazonian tropical forest Ana C.M. Malhado a, *, Marcos H. Costa a , Francisca Z. de Lima a , Kleber C. Portilho b , Daniel N. Figueiredo b a Biosphere-Atmosphere Research Group, The Federal University of Vic ¸osa, Vic ¸osa, MG, 36570-000, Brazil b LBA Office, Santare ´m, PA, Brazil 1. Introduction Anthropogenic changes in temperature and rainfall patterns are predicted to significantly influence vegetation dynamics and the spatial distribution of different biomes with accompanying changes in albedo and evapotranspiration which, in turn, feedback into global climate systems (e.g. Foley et al., 2003). The feedback between climate and vegetation dynamics is, of course, universal but may be particularly important in certain ecosystems, such as tropical forests, because of their enormous size and correspond- ingly vast stores of carbon. Unsurprisingly then, much attention has focused on the role of the Amazon, the Earth’s largest remaining area of continuous rainforest, in global change research. For example, Amazonian forests are thought to store 120  30 Pg C of biomass carbon (Malhi et al., 2006). In a recent review, Malhi et al. (2008) identified several ways in which the Amazon may influence global and regional climate cycles: first, widespread deforestation can have a positive feedback on externally forced climate change. It is thought that the Amazon had lost about 837,000 km 2 of forest by 2001 (Soares-Filho et al., 2006) and has lost a staggering 25,000 km 2 year 1 to deforestation throughout the 1990s (Achard et al., 2002). Second, intact forests, especially those in fertile western Amazonia may represent a carbon sink. Third, some models have predicted that continuing loss of forest may interfere with regional precipitation cycles and cause a qualitative change to a drier climate regime across the region (Costa and Foley, 2000; Senna et al., 2009). Finally, deforestation induced changes in aerosol loading may also influence regional patterns of precipitation. Monitoring and modelling the local and global effects of climate changes on the ecology of the Amazon rainforest is clearly essential for the development of effective mitigation and adaptation strategies and for effective forest management. It is equally clear that realistic climate models crucially depend on accurate data on vegetation dynamics and should ideally include information on several biophysical variables of the vegetation. One of the greatest barriers to the development of truly predictive simulations is the difficulty in obtaining detailed and realistic information on parameters such as plant cover, growth rate, biomass, etc. This gap in information is especially apparent in the Amazon rainforest where issues of scale and the technical challenge of estimating a complex interrelated suite of ecological metrics have hampered the development of sufficiently sophisticated assessment and monitoring programmes. Understanding the vegetation dynamics of forests requires an in-depth knowledge of changes in roots, stems, branches and leaves over time, and how these tree characteristics vary in relation to important environmental variables. Assessing the leaf dynamics of forest trees is especially challenging since turnover is often high Forest Ecology and Management 258 (2009) 1161–1165 ARTICLE INFO Article history: Received 8 April 2009 Received in revised form 30 May 2009 Accepted 2 June 2009 Keywords: Amazon Leaf area index Leaf residence time Leaf mortality Leaf biomass Leaf growth rate ABSTRACT The ecological consequences of climate change for large tropical forests such as the Amazon are likely to be profound. Amazonian forests strongly influence regional and global climates and therefore any changes in forest structure, such as deforestation or die-back, may create positive feedback on externally forced climate change. Monitoring, modelling and managing the impacts of anthropogenic climate change on forest dynamics is therefore an important objective of forest researchers, and one that requires long-term data on changes at the level of community, populations and phenotypes. In this paper we provide the most comprehensive study yet on the seasonal dynamics of various leaf traits: leaf area index (LAI), leaf mortality (LM), leaf biomass (LB), leaf growth rate (LG), and leaf residence time (TR) from 50 experimental plots in a forest site at Belterra, Para ´ State, Brazil. From this study we estimate annual mean leaf area index (LAI) to be 5.07 m 2 m 2 and annual mean leaf dry biomass to be 0.621 kg m 2 . The typical leaf grew at 0.049 kg m 2 month 1 and remained on the tree for 12.7 months. We compare these results to other similar studies and critically discuss the factors driving leaf demographics in Amazonia. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +55 31 3899 1902; fax: +55 31 3899 2735. E-mail addresses: anaclaudiamalhado@gmail.com, ana.malhado@geog.ox.ac.uk (Ana C.M. Malhado). Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco 0378-1127/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2009.06.002