Evaluation of Water Use Efficiency of Short Rotation Poplar Coppice at Bohemian

0480336 - ÚVGZ 2018 AT eng C - Konferenční příspěvek (zahraniční konf.)
Hlaváčová, Marcela - Fischer, Milan - Tripathi, Abishek - Orság, Matěj - Trnka, Miroslav
Evaluation of Water Use Efficiency of Short Rotation Poplar Coppice at Bohemian.
Geophysical Research Abstracts. Vídeň: European Geosciences Union, 2015. Geophysical Research Abstracts, 17. ISSN 1607-7962
Institucionální podpora: RVO:86652079

The water availability of the locality constitutes one of the main constraint for short rotation coppices grown on
arable land. As a convenient characteristic assessing how the water use is coupled with the biomass yields, so
called water use efficiency (WUE) is proposed. One method of water use efficiency determination is presented
within this study. The study was carried out at short rotation poplar coppice (poplar clone J-105) at the Test Station
Domanínek, Ltd. at Bohemian-Moravian Highlands during the growing season 2013. Diameters at breast height
(DBH) were measured for 16 sample trees where sap flow measuring systems (Granier’s Thermal Dissipation
Probe, TDP) were installed. TDP outputs are expressed as temperature differences (∆T) between the heated and
non-heated probes. Estimation of sap flux density (Fd) by the Granier method relies on the measurement of temperature
difference (∆T). Determination of maximum temperature difference (∆Tmax) is fundamental for sap
flux density (Fd) calculation. Although ∆Tmax can be theoretically defined as ∆T at Fd = 0, many factors may
prevent the occurrence of the zero flow state, such as night-time water movement for new growth (vegetative or
reproductive) or water loss from the canopy due to high vapour pressure deficit (VPD). Therefore, the VPD condition
was established for determination of ∆Tmax. VPD condition was established as follows: VPD reaching
values 0.2 at least 6 hours during night (from 21 p. m. to 3 a. m. and when the condition was fullfilled, the value at
3 a. m. was taken) because it is a supposed time after that the tree has no transpiration. The programmable part of
Mini 32 software (www.emsbrno.cz) was used for application of the script establishing ∆Tmax values under this
VPD condition. Nevertheless, another script was applied on ∆T data set to determination of ∆Tmax values for
every night at 3 a. m. (as this is when ∆T should be at its daily maximum) without VPD condition restriction for
comparison of both approaches. Since application of the two mentioned scripts led to two sets of resulting values,
calculations of Fd and consequent sap flow values were computed for both variants of ∆Tmaxvalues. The sample
trees were divided into 3 diameter classes according to DBH values at the beginning of regular measurements
(April 24, 2013). Allometry was carried out on February 20, 2014 to calculation of aboveground woody biomass.
The input data for calculations of WUE of aboveground woody biomass productivity was biomass increments and
monthly totals of sap flow for 16 sample trees. The total WUE for 16 measured trees reached 4.93 g kg−1
(when
calculated with data set without VPD condition) and 4.63 g kg−1
(when calculated with data set under VPD condition).
This study was funded by project "Building up a multidisciplinary scientific team focused on drought" No.
CZ.1.07/2.3.00/20.0248 and LD130030 supporting COST Action ES1106.
Trvalý link: http://hdl.handle.net/11104/0276135