Raffelsbauer, V.; Pucha-Cofrep, F.; Strobl, S.; Knüsting, J.; Schorsch, M.; Trachte, K.; Scheibe, R.; Bräuning, A.; Windhorst, D.; Bendix, J.; Silva, B. & Beck, E. (2023): <b>Trees with anisohydric behavior as main drivers of nocturnal evapotranspiration in a tropical mountain rainforest</b>. <i>PloS ONE </i> <b>18</b>(3), 1-1.
Resource Description
Title:
Trees with anisohydric behavior as main drivers of nocturnal evapotranspiration in a tropical mountain rainforest
email:
bendix <at> staff.uni-marburg.de
Faculty of Geography
Deutschhausstraße 10
Philipps University of Marburg
Laboratory for Climatology and Remote Sensing
35032 Marburg
Germany
email:
erwin.beck <at> uni-bayreuth.de
Universitätsstr. 30
Faculty of Biology, Chemistry and Geoscience
University of Bayreuth
95440 Bayreuth
Germany
Abstract:
This study addresses transpiration in a tropical evergreen mountain forest in the Ecuadorian<br/>
Andes from the leaf to the stand level, with emphasis on nocturnal plant-water relations. The<br/>
stand level: Evapotranspiration (ET) measured over 12 months with the Eddy-Covariance<br/>
(ECov) technique proved as the major share (79%) of water received from precipitation. Irre-<br/>
spective of the humid climate, the vegetation transpired day and night. On average, 15.3%<br/>
of the total daily ET were due to nocturnal transpiration. Short spells of drought increased<br/>
daily ET, mainly by enhanced nighttime transpiration. Following leaf transpiration rather<br/>
than air temperature and atmospheric water vapor deficit, ET showed its maximum already<br/>
in the morning hours. The tree level: Due to the humid climate, the total water consumption<br/>
of trees was generally low. Nevertheless, xylem sap flux measurements separated the<br/>
investigated tree species into a group showing relatively high and another one with low sap<br/>
flux rates. The leaf level: Transpiration rates of Tapirira guianensis, a member of the high-<br/>
flux-rate group, were more than twice those of Ocotea aciphylla, a representative of the<br/>
group showing low sap flux rates. Representatives of the Tapirira group operated at a rela-<br/>
tively high leaf water potential but with a considerable diurnal amplitude, while the leaves of<br/>
the Ocotea group showed low water potential and small diurnal fluctuations. Overall, the<br/>
Tapirira group performed anisohydrically and the Ocotea group isohydrically. Grouping of<br/>
the tree species by their water relations complied with the extents of the diurnal stem circum-<br/>
ference fluctuations. Nighttime transpiration and hydrological type: In contrast to the isohy-<br/>
drically performing trees of the Ocotea group, the anisohydric trees showed considerable<br/>
water vapour pressure deficit (VPD)-dependent nocturnal transpiration. Therefore, we con-<br/>
clude that nighttime ET at the forest level is mainly sourced by the tree species with aniso-<br/>
hydric performance.
