BSc-MSc (Integrated)

A study on “Modelling soil carbon dynamics of two major ecosystems of
humid tropics” was carried out in the Academy of Climate Change Education and
Research (ACCER) during 2014-2015. The study was done using two soil carbon
models such as Roth-C and CENTURY. The objectives of the study included the
evaluation of suitability of these two models in rice and teak ecosystems and also to
analyse the soil organic carbon changes due to predicted climate change scenarios.
The study was based on secondary data sets collected from experiments done
in paddy fields and teak plantations of Pattambi and Thrissur areas respectively
belonging to humid areas.
The simulated total soil organic carbon (1965 to 2050) by Roth-C and CENTURY
models was found to be declining in rice ecosystem. The active carbon in rice
ecosystem showed decreasing trend and thereafter it was showing an increasing trend.
In case of slow carbon it showed a gradual declining trend during the period from
1965 to 1990. There after it started to increase in a rapid manner during the next
eleven years and afterwards it started decreasing. The passive carbon in rice
ecosystem kept on increasing throughout the simulation period.
In teak ecosystem, both the models Roth-C and CENTURY predicted a
declining trend of total soil organic carbon. The active carbon of teak ecosystem
decreased by the end of third year and slowly increased by ninth year. By the end of
fifty five year it showed a rapid decline and slowly increased by the following years.
Slow carbon pool showed a declining trend up to thirty years and kept on increasing
to the next thirty years. Then it showed a rapid decline and thereafter it started to
increase. The passive carbon kept on decreasing throughout the period.
The model efficiency of Roth-C and CENTURY models for rice ecosystem
were 0.63 and 0.82, respectively whereas for teak ecosystem the values were 0.69 and
0.88. Hence it was concluded that for simulation of soil organic carbon, both the
models are suitable, but CENTURY model was more efficient than Roth- C model.
From the study based on different RCP scenarios, RCP 8.5 had predicted
higher temperature and precipitation values compared to others (RCP 6.0, RCP 4.5
and RCP 2.6) over both Pattambi and Vellanikkara. In rice ecosystem, it was noticed
that in 2015 and 2050, RCP 2.6 recorded the highest values of total soil organic
carbon and the lowest values were by RCP 8.5, respectively. In the case active
carbon, RCP 4.5 recorded the highest values and RCP 8.5 recorded the lowest values.
The highest value of slow carbon was recorded by RCP 2.6 and the lowest by RCP
8.5. The predicted values of passive carbon showed highest values by RCP 6.0 and
recorded the lowest by RCP 4.5.
In the study based on predicted climate change scenarios in teak ecosystem,
RCP 4.5 recorded highest values of total soil organic carbon in 2015 and 2050 where
as the lowest value was found by RCP 6.0 in 2015 and RCP 8.5 in 2050. The highest
value of active carbon was found in 2015 by RCP 4.5 and in 2050 by RCP 2.6. The
lowest values of active carbon were recorded by RCP 6.0 and RCP 8.5 in 2015 and
2050 respectively. In 2015 the highest value of slow carbon was recorded by RCP 4.5
and in 2050 by RCP 2.6. The least value of slow carbon was recorded in 2015 by
RCP 6.0 and in 2050 by RCP 8.5. The passive carbon simulated by different RCPs, it
was observed that RCP 4.5 predicted the highest value in 2015 and 2050. Then the
lowest values recorded by RCP 6.0, respectively
The present study indicated that modelling is suitable for studying carbon
dynamics in soils under rice and teak ecosystems. It highlights the potential of
CENTURY model over Roth-C model in terms of simulation of soil carbon. Using
different scenarios it is possible to know that, what might be the future conditions of
soil carbon and its different pools.