Guidelines

Document Sample
Guidelines Powered By Docstoc
					           SIMULATION IN PLANT-WATER RELATION: A CASE STUDY FOR HUNGARY
                                                       1                  2
                                   Angela Anda and László Dióssy
                                                                                          1
           University of Pannonia Georgikon Faculty P. O. Box 71 Keszthely Hungary H-8361
                                    E-mail: anda-a@georgikon.hu
                                                                                       2
             Ministry of Environment and Water P. O. Box 351 Budapest Hungary H-1394
                                     E-mail: diossy@mail.kvvm.hu

Abstract

We investigated the Hungarian consequences of global climate change on the basis of the simulated
stomatal resistance, transpiration and other plant characteristics as carbon-assimilation with the help
of Goudriaan’s Crop Microclimate Simulation Model, CMSM (Goudriaan 1977, Goudriaan and van
Laar 1984). To represent the expected modifications, Keszthely’s „average” weather, maize and soil
characteristics in July in the time period of 1961-1990 served as a starting point. We collected all
meteorological, plant and soil data locally during the past three decades. Beside the downscaled IPCC
A2 and B2 SRES scenarios Bartholy et al. (2007), which mean the „average” change in the individual
scenarios, our analysis also covered some extreme hot days, which has recently increased in number.
Altogether we applied eight scenarios including data of the past decade as well. The model calculates
the energy proportioning within the canopy after the reflection and transmission processes. After
calculating the sensible and latent heat fluxes, the micro-meteorological elements (air temperature,
humidity) and plant characteristics in the i layer may be estimated. The validation of modelled values
(stomatal resistance, photosynthesis, elements of microclimate) was carried out locally by earlier
investigations (Anda 2004, Anda and Lőke 2003, Anda et al. 1997). Model runs were evaluated by
using paired t-test that was performed by the free version of STATA 5.0 (1996) program package. The
process reduces the two-sample t-test to one-sample test since there is no possibility of repetition (so
of calculation of standard deviation) at the model runs. The significance level was fixed at 5% in the
course of the process.
         The basis result of simulation is the ratio if sensible and latent heat fluxes of applied eight
scenarios (Fig.1). Although the daily means have hardly changed, their diurnal variation varied.
Modification in plant properties related to climatic changes showed dependence on solar radiation
angle also.



                                                                      Sensible heat    Latent heat

                          100
                           80
              Energy, %




                           60
                           40
                           20
                            0
                                1961-   1997-   1961-90 1961-90 1961-90 1961-90 1961-90 1961-90
                                1990    2006    2XCO2 +3,8°C +4,8°C +6,0°C +9,0°C /1 +9,0°C /2
                                                           Scenario



  Fig. 1 Simulation of the ratio of sensible and latent heat fluxes in maize stand at Keszthely (July).
  Abbreviations of the x-axes are as follows: time periods; size of air temperature increase (sign +);
  /1: 10% precipitation depression; /2: 30% precipitation decrease. Doubled CO 2 concentration was
                               used from the third treatment, continuously.
         The use of the simulations containing relative large warming up was facilitated by the daily
distribution of the model. The daily average of stomatal resistance has significantly increased in all
scenarios, so has in the last decade (1997-2006). The doubled CO2 together with the unchanged
weather approximately halves stoma openings. It can be considered the advantageous impact of the
global warming up on the plant’s water loss since precipitation supply is scarce in Hungary. In scenario
A2 and B2 the increase of resistance was close to the one in the scenario containing doubled CO 2
concentration. It was a surprise that the increase of resistance in the extreme hot days was under the
expected. The common impact of the environmental and biological factors has been realized at the
normalized LAI values of daily average resistances, where the increases of stomatal resistance of
days simulating the highest warming up and having the highest precipitation decrease became the
highest ones compared to control. The daily evaporation and monthly transpiration amounts followed
the modifications of stomatal resistance, though we registered significant differences only in the
extreme hot days and at precipitation decrease of 30%. The development of the evaporation in
Keszthely has shown a certain amount of available soil humidity reserve even in the extreme
situations. Probably this is why fallback in the intensity of photosynthesis is not expected in the case of
either A2 or B2 scenarios. Decrease in carbon assimilation can occur in days with extreme
temperatures. Our scenarios did not contain significant precipitation decreases due to the forecast
uncertainties of the element. A significant precipitation decrease would fundamentally reshape our
results, so we do not propose to extend our conclusions in the case of significant modification in
precipitation.
         By now the warming up forecast to 2071-2100 has become an accepted prognosis, even by
its former opponents. Unfortunately there are rather uncertain concepts pertaining to the expected
precipitation. By knowing this the right way could be that we try to prepare some directions of the
changes in precipitation associated with warming up. The users of the presented scenarios do the
right thing if they do not forget about the results of the extreme hot days beside the scenarios
containing “average” weather.


Key-words: water relation, simulation model, global warming-local consequences

References

Anda A. 2004. Determination of the site of the mean stomatal resistance characteristics for
the whole plant. Acta Physiol. Plantarum, 26. 3:79-80.

Anda A. and Lőke Zs.2003. Simulation of factors influencing maize transpiration: stomatal
resistance, crop temperature and intensity of photosynthesis. (In Hungarian) Növénytermelés, Tom 52.
3-4:351-363.

Anda A., Páll J. and Lőke Zs. 1997. Measurement of mean stomatal resistance in maize.
Időjárás Vol. 101. 4:275-288.

Bartholy, J., Pongrácz, R., Gelybó, Gy. 2007. Regional climate change in Hungary for 2071-2100.
Applied Ecology and Environment Research 5: 1-17.

Goudriaan J. 1977. Crop Micrometeorology: A Simulation Study. Simulation Monographs. Pudoc,
Wageningen

Goudriaan, J. and van Laar, H. H. 1994: Modelling Potential Crop Growth Processes. Kluwer
Academic Publishers, Dordrecht-Boston-London. p:238

SRES 2000: Emission Scenarios. IPCC Summary for Policymakers. www.ipcc.ch/pdf/special-
reports/spm/sres-en.pdf

STATA 5.0 (1996) Stata Corporation LP Texas, USA. Available online: www.stata.com