Miguel F.Acevedo
ABSTRACTS
POTENTIAL EFFECTS OF GLOBAL CLIMATIC CHANGE ON THE PHENOLOGY AND YIELD
OF MAIZE IN VENEZUELA
Climatic
Change 29:189-211. 1995
Carlos E. Maytin 1, Miguel F. Acevedo 2,3, Ramon Jaimez 3, Rigoberto
Andressen
1,4, Mark A. Harwell 5, Alan Robock 6 and Aura Azocar 1
1 Centro de Investigaciones Ecologicas de los Andes Tropicales
(CIELAT),
Facultad de Ciencias, Universidad de Los Andes, Merida 5101, Venezuela.
2 Institute of Applied Sciences and Department of Geography, University
of North Texas, Denton TX 76203, USA. 3 Centro de Investigacion y
Proyectos
en Simulacion y Modelos (CESIMO), Facultad de Ingenieria, Universidad
de
Los Andes, Merida 5101, Venezuela. 4 Centro de Estudios Avanzados del
Clima
Tropical (CEACT), Ministerio del Ambiente y de los Recursos Naturales
Renovables
and Universidad de Los Andes, Merida, Venezuela. 5 Rosenstiel School of
Marine and Atmospheric Science, University of Miami, Miami FL, 33149,
USA.
6 Department of Meteorology, University of Maryland, College Park MD
20742,
USA.
A report of the PAN-EARTH Project, Venezuela Case Study
Abstract
Simulated impacts of global and regional climate change, induced by an
enhanced greenhouse effect and by Amazonian deforestation, on the
phenology
and yield of two grain corn cultivars in Venezuela (CENIAP PB-8 and
OBREGON)
are reported. Three sites were selected Turen, Barinas and Yaritagua,
representing
two important agricultural regions in the country. The CERES-Maize
model,
a mechanistic process-based model, in the Decision Support System for
Agrotechnology
Transfer (DSSAT) was used for the crop simulations. These simulations
assume
non-limiting nutrients, no pest damage and no damage from excess water;
therefore, the results indicate only the difference between baseline
and
perturbed climatic conditions, when other conditions remain the same.
Four
greenhouse-induced global climate change scenarios, covering different
sensitivity levels, and one deforestation-induced regional climate
change
scenario were used. The greenhouse scenarios assume increased air
temperature,
increased rainfall and decreased incoming solar radiation, as derived
from
atmospheric GCMs for doubled CO2 conditions. The deforestation
scenarios
assume increased air temperature, increased incoming solar radiation
and
decreased rainfall, as predicted by coupled atmosphere-biosphere models
for extensive deforestation of a portion of the Amazon basin. Two
baseline
climate years for each site were selected, one year with average
precipitation
and another with lower than average rainfall.
Scenarios associated with the greenhouse effect cause a decrease in
yield of both cultivars at all three sites, while the deforestation
scenarios
produce small changes. Sensitivity tests revealed the reasons for these
responses. Increasing temperatures, especially daily maximum
temperatures,
reduce yield by reducing the duration of the phenological phases of
both
cultivars, as expected from CERES-Maize. The reduction of the duration
of the kernel filling phase has the largest effect on yield. Increases
of precipitation associated with greenhouse warming have no effects on
yield, because these sites already have adequate precipitation;
however,
the crop model used here does not simulate potential negative effects
of
excess water, which could have important consequences in terms of soil
erosion and nutrient leaching. Increases in solar radiation increased
yields,
according to the non-saturating light response of the photosynthesis
rate
of a C4 plant like corn, compensating for reduced yields from increased
temperatures in deforestation scenarios. In the greenhouse scenarios,
reduced
insolation (due to increased cloud cover) and increased temperatures
combine
to reduce yields; a combination of temperature increase with a
reduction
in solar radiation produces fewer and lighter kernels.
Key words: mayze, deforestation, climate change, Venezuela
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