Fig. 1.

Seasonal changes in canopy LAI and understory LAI over the Amazon. Each 1° pixel represents the mean canopy LAI change (A–C) or understory LAI change (D–F) for three GLAS acquisition periods: March to June, June to October, and October to March (of the following year), using data pooled from 2003 to 2006. In all cases, the LAI change is expressed as the later period minus the earlier one. Spatial distribution of canopy greening-up coincides with the approximate start of dry season but in an asynchronous mode (A–C), as different parts of Amazon have different starting months of the dry season (Table 1 and Fig. S2). The understory also shows a seasonal cycle (D–F) but with an opposite variation to canopy. Note the different scale bars between canopy and understory. Gray pixels represent areas where the observed mean LAI change is less than standard error for that cell (Materials and Methods).