Effects of geography (longitude, latitude and elevation) on GF status in regional-scale GF episodes examined by generalized linear mixed models with binomial error structure.

*<p>p<0.05,</p>***<p>p<0.001,</p><p>The forest id was used as a random effect in the models.</p

Geographical Pattern and Environmental Correlates of Regional-Scale General Flowering in Peninsular Malaysia

<div><p>In South-East Asian dipterocarp forests, many trees synchronize their reproduction at the community level, but irregularly, in a phenomenon known as general flowering (GF). Several proximate cues have been proposed as triggers for the synchronization of Southeast Asian GF, but the debate continues, as many studies have not considered geographical variation in climate and flora. We hypothesized that the spatial pattern of GF forests is explained by previously proposed climatic cues if there are common cues for GF among regions. During the study, GF episodes occurred every year, but the spatial occurrence varied considerably from just a few forests to the whole of Peninsular Malaysia. In 2001, 2002 and 2005, minor and major GF occurred widely throughout Peninsular Malaysia (GF2001, GF2002, and GF2005), and the geographical patterns of GF varied between the episodes. In the three regional-scale GF episodes, most major events occurred in regions where prolonged drought (PD) had been recorded prior, and significant associations between GF scores and PD were found in GF2001 and GF2002. However, the frequency of PD was higher than that of GF throughout the peninsula. In contrast, low temperature (LT) was observed during the study period only before GF2002 and GF2005, but there was no clear spatial relationship between GF and LT in the regional-scale episodes. There was also no evidence that last GF condition influenced the magnitude of GF. Thus, our results suggest that PD would be essential to trigger regional-scale GF in the peninsula, but also that PD does not fully explain the spatial and temporal patterns of GF. The coarse relationships between GF and the proposed climatic cues may be due to the geographical variation in proximate cues for GF, and the climatic and floristic geographical variations should be considered to understand the proximate factors of GF.</p></div

Distribution patterns of major and minor GF (left), and meteorological stations with PD (centre) and LT (right) during the three regional-scale GF episodes.

<p>Plots show the presence or absence of PD and LT during the putative floral induction season: June–August (GF2001) or January–March (GF2002 and GF2005).</p

Effects of last GF status and the two plausible meteorological cues (PD and LT) on GF status.

*<p>p<0.05.</p><p>Results from GLMM using with binomial error structure were shown. The forest id was used as a random effect in the models.</p

Summary of climate at 14 meteorological stations in Peninsular Malaysia.

*<p>p<0.05,</p>**<p>p<0.01,</p>***<p>p<0.001.</p

Geographical distribution of GF from November 2001 to June 2005.

<p>Each site was scored for the density of fruiting dipterocarp trees (major GF, minor GF, sporadic fruiting or none). (a) Topography of Peninsular Malaysia. (b, d, f, h) GF scores in November–December 2001–2005 (the autumn type). (c, e, g, i) GF scores in June-July 2002–2005 (the spring type).</p

Occurrences of ENSO, PD and LT in Peninsular Malaysia from 2001 to 2005.

<p>(a) Niño 3 values as ENSO index, (b) months with PD (30-day moving total rainfall <40 mm) and (c) months with LT (daily minimum temperature <20°C). An El Niño episode occurred from summer 2002 to winter 2002–03, and La Niña from winter 2005 to spring 2006. Arrows indicate regional-scale GF episodes (GF2001, GF2002 and GF2005). Station names are identified in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079095#pone-0079095-t002" target="_blank">Table 2</a>.</p