Agriculture Reference
In-Depth Information
Fig. 7.6 Effect of minimum temperature and rainfall on incidence of barley aphids
were also found to be negatively related
( r = −0.27, Fig. 7.6 ). Therefore, the rise in mini-
mum temperature and more intense rains in the
future as speculated might reduce aphid inci-
dence on barley.
The model was used to simulate the impact of
global warming on the rice bug by altering daily
minimum and maximum temperatures. It could
be concluded that up to 1 °C rise in daily average
temperature over the present temperature of
Delhi would not affect the gundhi bug population
much, but further increase would cause appre-
ciable decline in its population.
7.18.4 Simulation Models
Simulation models have been used widely to
assess the impact of climate change on yield
of various crops in different agroecological zones.
7.18.4.2 Coupling of Population
Dynamics Model to Crop
Growth Simulation Model
The population dynamics model can be coupled
to crop growth model at the appropriate level of
plant processes, depending on the pest damage
mechanisms. The damaging pest stage affects
plant growth and yield based on its number and
feeding rate of individuals. Crop pest model can
then be used to analyze the impact of climate
change on crop productivity, insect dynamics, as
well as crop-pest interactions.
7.18.4.1 Simulation of Population
Dynamics
Insect population dynamics model can be devised
based on various bioecological factors, viz., fecun-
dity, sex ratio, migration, abiotic and biotic mortal-
ity factors, threshold of development, and thermal
constant. Chander et al. ( 2009 ) have developed
such a model for rice gundhi bug, Leptocorisa
acuta , which is comprised of state, rate, driving,
and auxiliary variables (Fig. 7.7 ). State and rate
variable approach was followed in developing the
model. Insect population converted from one stage
to another in proportion to the ratio of effective
temperature to thermal constant of that stage and
stage-specifi c mortality. Depending upon the rate
of population change, total insect number in each
developmental stage was updated daily.
7.19
Adaptation
Adaptation refers to an adjustment in natural or
human systems in response to actual or expected
climatic stimuli or their effects that moderate,
harm, or exploit benefi cial opportunities.
 
Search WWH ::




Custom Search