PS 6-55 - Management impacts on forest carbon balance

Monday, August 3, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Daniel P. Bebber1, Terhi Riutta2, Nancy Khan3, Jeffrey Lombardo3, Robson Capretz4 and Indu Murthy5, (1)Earthwatch Institute, Oxford, United Kingdom, (2)Centre for the Environment, University of Oxford, Oxford, United Kingdom, (3)Smithsonian Environmental Research Center, Edgewater, MD, (4)Sociedade de Pesquisa em Vida Selvagem e Educação Ambiental, Curitiba, Brazil, (5)Centre for Ecological Studies, Indian Institute of Sciences, Bangalore, India
Forest carbon stocks and fluxes are amongst the least well-defined elements of the global carbon cycle, and great uncertainty remains in predicting the effect of climate change on forest dynamics. Human activities at varying scales and intensities also influence forest carbon directly, and through interactions with climate. In some cases, the management-climate interaction is well known, for example through increased fire susceptibility when tropical forests are logged. Elsewhere, these interactions are poorly understood, but are likely to be important in improving modelling of climate change, and in valuing forest carbon.  To improve understanding of management-climate interactions, a network of permanent sample plots has been established in five sites around the world – in the UK, USA, Brazil, India and China. The sites are near larger CTFS plots to facilitate comparisons. At each site, 1-ha plots have been placed in forest stands with differing management regimes and histories. Within each plot, all trees >5cm dbh are tagged, mapped, identified to species, and diameter is recorded. A subset of trees have dendrometer bands attached, to record seasonal change in growth. Dead wood and litterfall samples are taken. Microclimate is recorded using automatic sensors. Serial measurements will allow correlation of forest dynamics with weather.
The studies are at an early stage therefore results are incomplete. Above-ground biomass estimates are 300-350 t ha-1 for mature Liriodendron tulipifera-dominated stands in the USA, 200-300 t ha-1 for mature semi-natural evergreen sites in India, and 200-300 t ha-1 for plantations and semi-natural stands in the UK. Data from Brazil and China have not yet been analysed. In the UK, plantations had greater biomass than the semi-natural plots, due to differences in age structure. In the semi-natural plots, trees above 50 cm dbh comprised just 3% of stems but almost 50% of the biomass. A lack of regeneration of larger species suggest future insecurity of carbon stores in these stands. No strong edge-effects on biomass were detected, but future comparisons with smaller forests will enable estimation of fragmentation effects on biomass pools and dynamics. Preliminary data on biomass and spatial patterns of trees, litterfall, and microclimate are presented for three of five sites. Comparisons are made among the modes of forest disturbance, and how these could influence ecosystem responses to climate. Increasing human and climatic pressures on the world's forests will necessitate further studies of this type.
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