报告题目:陆地水文对热带雨林光合作用的影响
报告人:Dr. Ming Pan
单位:Department of Civil and Environmental Engineering, Princeton University, USA
时间:2015年3月20日上午10:00
地点:大气所40号楼319会议室
摘要:The response of tropical forests to droughts is highly uncertain. During the dry season,
canopy photosynthesis of some tropical forests can decline, whereas in others it can be maintained
at the same or a higher level than during the wet season. However, it remains uncertain to what
extent water availability is responsible for productivity declines of tropical forests during the dry
season. Here we use global satellite observations of two independent measures of vegetation
photosynthetic properties (enhanced vegetation index from 2002 to 2012 and solar-induced
chlorophyll fluorescence from 2007 to 2012) to investigate links between hydroclimate and tropical
forest productivity. We find that above an annual rainfall threshold of approximately 2,000 mm yr−1,
the evergreen state is sustained during the dry season in tropical rainforests worldwide, whereas
below that threshold, this is not the case. Through a water-budget analysis of precipitation,
potential evapotranspiration and satellite measurements of water storage change, we demonstrate
that this threshold determines whether the supply of seasonally redistributed subsurface water
storage from the wet season can satisfy plant water demands in the subsequent dry season. We
conclude that water availability exerts a first-order control on vegetation seasonality in tropical
forests globally. Our framework can also help identify where tropical forests may be vulnerable
or resilient to future hydroclimatic changes.