Species-Specific Shifts in Diurnal Sap Velocity Dynamics and Hysteretic Behavior of Ecophysiological Variables During the 2015-2016 El Nino Event in the Amazon Forest
VAPOR-PRESSURE DEFICIT
; STOMATAL CONDUCTANCE
; RAIN-FOREST
; HEAT PULSE
; EVAPORATIVE DEMAND
; CIRCADIAN-RHYTHMS
; TROPICAL FORESTS
; WATER TRANSPORT
; FOLIAR UPTAKE
; TREE
WOS学科分类:
Plant Sciences
WOS研究方向:
Plant Sciences
英文摘要:
Current climate change scenarios indicate warmer temperatures and the potential for more extreme droughts in the tropics, such that a mechanistic understanding of the water cycle from individual trees to landscapes is needed to adequately predict future changes in forest structure and function. In this study, we contrasted physiological responses of tropical trees during a normal dry season with the extreme dry season due to the 2015-2016 El Nino-Southern Oscillation (ENSO) event. We quantified high resolution temporal dynamics of sap velocity (V-s), stomatal conductance (g(s)) and leaf water potential (psi(L)) of multiple canopy trees, and their correlations with leaf temperature (T-leaf) and environmental conditions [direct solar radiation, air temperature (T-air) and vapor pressure deficit (VPD)]. The experiment leveraged canopy access towers to measure adjacent trees at the ZF2 and Tapajos tropical forest research (near the cities of Manaus and Santarem). The temporal difference between the peak of g(s) (late morning) and the peak of VPD (early afternoon) is one of the major regulators of sap velocity hysteresis patterns. Sap velocity displayed species-specific diurnal hysteresis patterns reflected by changes in T-leaf. In the morning, T-leaf and sap velocity displayed a sigmoidal relationship. In the afternoon, stomatal conductance declined as Tleaf approached a daily peak, allowing psi(L) to begin recovery, while sap velocity declined with an exponential relationship with T-leaf. In Manaus, hysteresis indices of the variables T-leaf-T-air and psi(L)-T-leaf were calculated for different species and a significant difference (p < 0.01, alpha = 0.05) was observed when the 2015 dry season (ENSO period) was compared with the 2017 dry season ("control scenario"). In some days during the 2015 ENSO event, T-leaf approached 40 degrees C for all studied species and the differences between T-leaf and T-air reached as high at 8 degrees C (average difference: 1.65 +/- 1.07 degrees C). Generally, T-leaf was higher than T-air during the middle morning to early afternoon, and lower than T-air during the early morning, late afternoon and night. Our results support the hypothesis that partial stomatal closure allows for a recovery in psi(L) during the afternoon period giving an observed counterclockwise hysteresis pattern between psi(L) and T-leaf.
1.Natl Inst Amazonian Res INPA, Manaus, Amazonas, Brazil 2.Lawrence Berkeley Natl Lab, Climate & Ecosyst Sci Div, Berkeley, CA USA 3.Univ Calif Berkeley, Dept Integrat Biol, Berkeley, CA 94720 USA 4.Embrapa Amazonia Oriental, Belem, Para, Brazil 5.Oak Ridge Natl Lab, Div Environm Sci, POB 2008, Oak Ridge, TN 37831 USA 6.Oak Ridge Natl Lab, Climate Change Sci Inst, Oak Ridge, TN USA 7.Los Alamos Natl Lab, Earth & Environm Sci Div, Los Alamos, NM USA 8.Pacific Northwest Natl Lab, Richland, WA 99352 USA 9.Univ Calif Berkeley, Dept Geog, Berkeley, CA 94720 USA
Recommended Citation:
Gimenez, Bruno O.,Jardine, Kolby J.,Higuchi, Niro,et al. Species-Specific Shifts in Diurnal Sap Velocity Dynamics and Hysteretic Behavior of Ecophysiological Variables During the 2015-2016 El Nino Event in the Amazon Forest[J]. FRONTIERS IN PLANT SCIENCE,2019-01-01,10