Australia: The Land Where Time Began

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Global Tropical Forests Seasonality Constrained by Hydroclimate

It is highly uncertain how tropical forests respond to droughts (Huntingford et al., 2013). Photosynthesis in some tropical forests can decline during the dry season, while others can maintain it at the same or higher levels than they reach in the wet season (Restrepo-Coupe, N. et al., 2013). It remains uncertain, however, to what extent declines of productivity in the dry season is caused by the availability of water (Restrepo-Coupe, N. et al., 2013; Saleska, de Rocha, Kruijt & Nobre, 2009). In this paper Guan et al. investigate links between hydroclimate and the productivity of tropical forests using global satellite observations of 2 independent measures of the photosynthetic properties of vegetation (enhanced vegetation index from 2002 to 2012, and from 2007 to 2012, solar-induced chlorophyll fluorescence). They found that the evergreen state is sustained during the dry season in tropical forests worldwide above an annual rainfall threshold of about 2,000 mm/yr, though this is not the case below that threshold. Guan, et al. used a water-budget analysis of precipitation, potential evapotranspiration and satellite measurements of changes in water storage to demonstrate that the seasonally redistributed subsurface water storage from the wet season can satisfy the demands for water in the subsequent dry season. Their conclusion is that in tropical forests globally a first-order control is exerted of the seasonality of vegetation. They also suggest that their framework could also help in the identification of tropical forests that may be vulnerable or resilient to Hydroclimate changes in the future.

Sources & Further reading

  1. Guan, K., M. Pan, H. Li, A. Wolf, J. Wu, D. Medvigy, K. K. Caylor, J. Sheffield, E. F. Wood, Y. Malhi, M. Liang, J. S. Kimball, S. R. Saleska, J. Berry, J. Joiner and A. I. Lyapustin (2015). "Photosynthetic seasonality of global tropical forests constrained by hydroclimate." Nature Geosci 8(4): 284-289.


Author: M. H. Monroe
Last updated: 11/04/2015
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