Bendix, J.; Silva, B.; Roos, K.; Göttlicher, D.; Rollenbeck, R.; Nauss, T. & Beck, E. (2009): <b>Model parameterization to simulate and compare the PAR absorption potential of two competing plant species</b>. <i>International Journal of Biometeorology</i> <b>OnlineFirs</b>, xx-xx.
Resource Description
Title:
Model parameterization to simulate and compare the PAR absorption potential of two competing plant species
Short Name:
Model parameterization
FOR816dw ID:
687
Publication Date:
2009-10-08
License and Usage Rights:
Resource Owner(s):
Individual:
Jörg Bendix
Contact:
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:
biene.tomate <at> gmx.net
Faculty of Biology, Chemistry and Geoscience
Department of Plant Physiology
Universitätsstr. 30
95440 Bayreuth
Germany
Individual:
Dietrich Göttlicher
Contact:
email:
dietrich.goettlicher <at> staff.uni-marburg.de
Faculty of Geography
Deutschhausstr. 10
Laboratory for Climatology and Remote Sensing
Philipps University of Marburg
35032 Marburg
Germany
Individual:
Ruetger Rollenbeck
Contact:
email:
rollenbe <at> staff.uni-marburg.de
Laboratory for Climatology and Remote Sensing
Faculty of Geography
Philipps University of Marburg
Deutschhausstr. 10
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:
Abstract Mountain pastures dominated by the pasture grass Setaria sphacelata in the Andes <br/>
of southern Ecuador are heavily infested by southern bracken (Pteridium arachnoideum), a major <br/>
problem for pasture management. Field observations suggest that bracken might outcompete the grass <br/>
due to its competitive strength with regard to the absorption of photosynthetically active radiation <br/>
(PAR). To understand the PAR absorption potential of both species, the main aim of the current paper <br/>
is to (i) parameterize a radiation scheme of a two-big leaf model by deriving structural (LAI, leaf angle <br/>
parameter) and optical(leaf albedo, transmittance) plant traits for average individuals from field <br/>
surveys, (ii) to initialise the properly parameterized radiation scheme with realistic global irradiation <br/>
conditions of the Rio San Francisco Valley in the Andes of southern Ecuador, and (iii) to compare the <br/>
PAR absorption capabilities of both species under typical local weather conditions. Field data show <br/>
that bracken reveals a slightly higher average leaf area index (LAI) and more horizontally oriented <br/>
leaves in comparison to Setaria. Spectrometer measurements reveal that bracken and Setaria are <br/>
characterised by a similar average leaf absorptance. Simulations with the average diurnal course of <br/>
incoming solar radiation (1998-2005) and the mean leaf-sun geometry reveal that PAR absorption is <br/>
fairly equal for both species. However, the comparison of typical clear and overcast days show that two <br/>
parameters, (i) the relation of incoming diffuse and direct irradiance, and (ii) the leaf-sun geometry <br/>
play a major role for PAR absorption in the two-big leaf approach: Under cloudy sky conditions (mainly <br/>
diffuse irradiance), PAR absorption is slightly higher for Setaria while under clear sky conditions <br/>
(mainly direct irradiance), the average bracken individual is characterized by a higher PAR absorption <br/>
potential. (~74 MJ m-2 a-1) . The latter situation which occurs if the maximum daily irradiance exceeds <br/>
615 W m-2 is mainly due to the nearly orthogonal incidence of the direct solar beam onto the <br/>
horizontally oriented frond area which implies a high amount of direct PAR absorption during the <br/>
noon maximum of direct irradiance. Such situations of solar irradiance favouring a higher PAR <br/>
absorptance of bracken occur in ~36% of the observation period (1998-2005). By considering the <br/>
annual course of PAR irradiance in the San Francisco Valley, the clear advantage of bracken on clear <br/>
days (36% of all days) is completely compensated by the slight but more frequent advantage of Setaria <br/>
under overcast conditions (64% of all days). This means that neither bracken nor Setaria show a <br/>
distinct advantage in PAR absorption capability under the current climatic conditions of the study area.
Literature type specific fields:
ARTICLE
Journal:
International Journal of Biometeorology
Volume:
OnlineFirs
Page Range:
xx-xx
Metadata Provider:
Individual:
Maik Dobbermann
Contact:
email:
dobberma <at> staff.uni-marburg.de
Laboratory for Climatology and Remote Sensing
Faculty of Geography
Deutschhausstr. 12
Philipps University of Marburg
35032 Marburg
Germany
