• 11:40 Improving understanding of the environmental controls of forest biomass and productivity: insights from permanent plot networks

  Stephenson, Nathan L; Das, Adrian J; van Mantgem, Phillip J

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  A mechanistic understanding of forest biomass and productivity depends, in part, on understanding of the population dynamics of strongly size-structured populations. While individual tree masses and productivity are functions of growth, at the scale of a forest stand the numbers of trees of different masses and productivities are functions of demographic rates (birth and death rates). Permanent plot networks, in which the fates of individual trees are tracked through time, can provide unique insights into environmental controls of demographic rates, thus potentially improving key assumptions in dynamic global vegetation models (DGVMs). As examples, we offer some findings from plot networks and suggest some implications for modeling. First, tree mortality rates follow global and regional patterns of site potential for productivity, with the most productive forest sites showing the highest mortality rates. Second, and contrary to some expectations, this pattern may be driven primarily by plant enemies (mostly insects and pathogens), not competition. That is, the same warm, moist environments that favor tree growth also favor the plant enemies that kill trees. Third, the latter finding argues for the importance of considering the effects of environmental changes not just individual tree physiology, but also on the higher trophic levels that influence tree population dynamics. Environmental effects on plant enemies can explain apparent paradoxes, such as lower forest biomass on sites with higher potential for productivity.

  
   

• 11:20 Biomass observations for an enhanced understanding of the terrestrial carbon cycle

  Carvalhais, Nuno (1,2); Matthias, Forkel (1); Martin, Thurner (3,1); Christian, Beer (3,1); Maurizio, Santoro (4); Markus, Reichstein (1) 1: Max-Planck-Institute for Biogeochemistry, Germany; 2: Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal; 3: Stockholm University, Sweeden; 4: Gamma Remote Sensing, Switzerland

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  Forests mediate the exchange of carbon, water and energy between the land surface and atmosphere and represent an important carbon sink globally. Improved knowledge of the spatial distribution and temporal dynamics of forest biomass is a prerequisite to understand the biotic and abiotic controls on long-term ecosystem dynamics. The emergence of mature remote sensing-based products of forest biomass provides a unique opportunity to evaluate our current understanding of the main mechanisms controlling the distribution of forests and the theoretical frameworks embedded in terrestrial ecosystem models. Here we provide examples, from in situ to regional and global spatial scales, on how exploring observations of forest biomass contribute to understanding the controls of the spatial variability of carbon stocks and related dynamics in Northern Hemisphere forests. By combining biomass observations with additional observation-based estimates of soil carbon stocks and fluxes we present a global analysis of whole ecosystem and vegetation carbon turnover times on land. Furthermore, we demonstrate how these datasets are unique in improving terrestrial biogeochemical cycle models, from testing alternative model formulations and providing consistent parameterizations in inverse modelling approaches, to the evaluation of carbon cycle dynamics in land surface schemes of state-of-the-art Earth System models. Model-data comparisons reveal substantial differences in the modelled temporal dynamics of carbon stocks and turnover times and its relationships with climate. These results reflect the current challenges in representing processes of growth, carbon allocation, and turnover in global terrestrial ecosystem models. These challenges emphasize the importance and value of upcoming remote sensing-based biomass retrievals to diagnose spatial variations of forest carbon and to integrate future multi-temporal information in Earth System models for an enhanced understanding and description of the terrestrial carbon cycle.

  
   

• 11:00 Modelling biomass dynamics at tropical sites in French guyana in the prospect of assimilation of spaceborne biomass measurements

  Nadjovski, Nicolas (1,2); Poulter, Benjamin (1); Chave, Jerome (3); Maignan, Fabienne (2); Luyssaert, Sebastiaan (2); Barichivitch, Jonathan (2); Peylin, Philippe (2); Ciais, Philippe (2,4) 1: Montana State University, United States of America; 2: Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL), France; 3: UMR 5174, Evolution et Diversité Biologique, France; 4: Sino-French Institute of Earth System Sciences, LSCE-IPSL and College of Urban and Environmental Sciences, Peking University

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  Process based models often termed as DGVMs struggle to simulate biomass, especially in tropical forest closed canopies since they consider well mixed carbon pools fed by NPP and reduced by ad-hoc mortality factors. Individual-based models are more suitable to this purpose but they may lack upscaling, require heavy computational resources and usually work on time steps that do not resolve fast physiological and gas exchange processes. A hybrid model is developed from the ORCHIDEE-CAN DGVM that resolves tree competition and its impact on the vertical structure of the canopy, and CO2, water and energy fluxes with the atmosphere. The model includes competition for light among different diameter classes, class-specific mortality and recruitment of young individuals. Applications and evaluation at site scale in French Guyana will be presented and prespects for the assimilation of spaceborne measurements of biomass and stand structure state variables

  
   

• 12:00 Plenary Discussion - BIOMASS

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  Plenary Discussion - BIOMASS

  
   

Highlights

In May 2013, the Biomass mission concept was selected to become the next in the series of satellites developed to further our understanding of Earth.

Released: 21/06/2013

REPLAY EARTH EXPLORER 7 USER CONSULTATION MEETING (PART 1)

Released: 11/03/2013

POLinSAR 2013 Workshop

Released: 22/02/2013