Figure 1.
Nine rainforest (blue) and fifteen dry forest (red) sites across six of the main Hawaiian Islands with precipitation isohyets (black lines).
Figure 2.
Comparison of relationship between rainforest and dry forest precipitation with rainforest and dry forest NDVI.
Relationship between windward and leeward precipitation anomalies from 9-year mean (P<0.001, r = 0.566, df = 107) (a). Rainforest and dry forest NDVI anomalies show no relationship (P = 0.475, r = 0.070, df = 104) (b).
Figure 3.
Asynchronous rainforest and dry forest NDVI and relationship to rainforest cloud frequency.
Rainforest NDVI (black line) and dry forest NDVI (grey line) showing 9-year leaf phenology on left axis, and windward precipitation (black line) and leeward precipitation (grey line) on right axis. Data shown are 3-month moving averages, while analyses were performed on monthly data (a). Average cloud frequency over rainforest sites for each 8-day period (grey bars) with 3-month moving average (black dotted line) on left axis and ΔNDVI (black line) on right axis (b). Grey bar highlighting 2002–2003 El Niño-driven drought.
Table 1.
Spearman rank correlations between rainforest NDVI and windward precipitation anomalies (N = 9, (*) two-tailed p<0.05, (**) p<0.01).
Table 2.
Spearman rank correlations between dry forest NDVI and precipitation anomalies (N = 9, (*) two-tailed p<0.05, (**) p<0.01).
Figure 4.
Spatial and temporal patterns in NDVI response to El Niño-driven drought.
Spearman rank correlation coefficients between NDVI anomalies from 9-year mean (2000–2008) and NINO 3.4 SST index, showing strongest leeward drought response (negative correlation) and windward green-up at an 8–9-month lag during 2002–2003 El Niño event (white regions are not statistically significant). (Precipitation isohyets on Fig. 1.)