SHIFT OF LITTERFALL TIMING DURING EXTREME CLIMATEIN SECONDARY DRY...
ABSTRACT
Climate change and variability could result in a shift of forest phenology. The climate extremesare further projected
to be more frequent and server under future climate change. Thus its impact on forest ecosystem is crucial for evaluating
forest carbon sequestration, adaptation and ecosystem services. However, our understanding of interaction between phenology
and climate extreme in tropical forest is still poor. In this study, we investigated the monthly litterfall production for eight
years(2009-2017) in a secondary dry dipterocarp forest in Thailand. During the study period, El Niño and La Niña were
observed and its impacts on litterfall were evaluated. During these eight years, the amount of total litter production was in the
range of 5.37-9.62Mg ha-1yr-1 and 70-85% of litter production occurred in dry season (November- April of the following year).
The trend of the annual litter production has increased. However, the annual litter production was significantly dropped in the
El Niño years, compared to other years. In the El Niño years (2009/2010 and 2015/2016), the peaks of litterfall production was
in January, a shift of 1-2 months earlier than in the other years. In contrast, in La Niña year (2010/2011) peak of litter
production was in March, delayed1-2 months. The litterfall production for five months between November to March was
related to the rainfall amount at two months preceding of litterfall timing, to the level of soil moisture at one month preceding
of litterfall timing and to vapor pressure deficit, with the coefficient correlation of -0.70, -0.62 and 0.53, respectively. In order
to quantify the effects of this phenological shift, currently the relationships among the end of season, carbon sequestration and
nutrient cycle in this forest ecosystem are being investigated.
