Figure 1: Time series of ground data and of the SPEI12 for the beech forest in Hesse.
From: Remotely-sensed detection of effects of extreme droughts on gross primary production
(a) SPEI12 and relative extractable water (REW); (b) leaf area index (LAI; determined from trapped litter; see29); (c) daily values for tower GPP; and (d) the results of the breakpoint analysis for GPP (with 8-day values). In (a), the blue line corresponds to SPEI12 and the black line to REW. The red line indicates the SPEI12 threshold of −1.5 (indicative of severe drought). Black symbols for LAI indicate the year after thinning. No thinning occurred in the years with open symbols for LAI. In (d), the seasonally adjusted data (abbreviated as ‘ad.’ in axis labels) are shown and the black line indicates the results of the breakpoint analysis. The grey area indicates the drought episode that is focused on in this study.
