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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
23 Soil and Vegetation — Atmosphere Fluxes:
The tower based flux measurements are reported to provide
unbiased regional estimates of CO; fluxes (Baldocchi et al.,
2001). Initial efforts were made to identify the needs and
approach for developing flux net work over India
(Sundareshwar et al., 2007). As part of National Carbon Project
(NCP) initiative of ISRO-GBP a nationwide network of carbon
towers in major forests, croplands and grasslands for the
measurement and modeling of the net carbon flux using eddy
covariance techniques, satellite remote sensing data and models
is planned. Accordingly the Soil and Vegetation — Atmosphere
Carbon Flux study is being conducted with the following
objectives:
* Analysis of atmospheric CO; patterns to study spatio
— temporal Carbon source-sink relations over India.
Establishment of flux towers and measurement of ed-
dy covariance and meteorological parameters to study
the exchanges of carbon dioxide (CO;), water vapour
and energy balance between terrestrial ecosystems
and the atmosphere.
Measurement and spatial modeling of soil CO; fluxes
Integration of observations and component — wise
modelling for conducting full carbon balance ac-
counting of India and estimation of net carbon bal-
©,
hd
53
SS
SO,
ee
ance.
Figure 2: showing Flux tower in Mangrove with sensors and
the approach to the tower
Three towers at forest sites of 15-50 m height at Barkot,
Uttaranchal; Haldwani, Uttaranchal and Betul, M.P. were
established. A new tower in mangrove forests of Sunderabans
(Figure2) has also established where methane flux is also being
measured in addition to CO, and water. The daily peak CH,
flux in the month of March 2012 was around 2 micromol/m/s.
Site specific studies was also conducted for measurement and
modeling of soil respiration and emission fluxes using
automatic soil CO; exchange system at Haldwani tower site.
One 3 meter tower at Agriculture site (Meerut) with open Path
flux tower has been installed in an agro-ecosystem at
Modipuram, Meerut to measure net CO, exchange between
atmosphere and crop canopy. The biophysical data thus
generated is being analysed to understand diurnal, seasonal and
inter annual variation in carbon and water fluxes and NPP
modeling using RS based models.
The 10 Hz micrometeorological data are processed inclusive of
various corrections to derive half-hourly fluxes of carbon,
water vapour and heat fluxes by using various softwares. Field
measurements such as leaf area index, soil moisture and
chlorophyll content index were measured at weekly interval.
Half-hourly photosynthetically active radiation above and
below wheat canopy was measured on a weekly basis. Daily
GPP and ecosystem respiration was computed from half-
hourly NEE after applying gap filling, filtering and nocturnal
NEE-temperature relationship. Day-time ecosystem respiration
was computed by applying temperature response function to
half-hourly temperature data.
Light-response curves and its parameters were derived at
different growth stages of wheat by fitting rectangular
hyperbolic functions between measured GPP and absorbed
photosynthetically active radiation. Diurnal pattern in Net
ecosystem exchange (NEE) reveals negative NEE during day-
time representing CO, uptake and positive during night as
release of CO;. The amplitude of the diurnal variation in NEE
increased with growth of wheat and reached its peak around the
pre-anthesis stage. The mid-day uptake during this stage was
around 1.15 mg CO, ms” and night-time release was around
0.15 mg CO; m?s'. Large daily GPP above 30 g CO, m?d'
continued until mid of anthesis stage (15 march) and decline
rapidly during maturity stage. (Patel et al., 2010 and Patel et al.
2011).
The Haldwani flux tower is established over mixed plantation
and natural forests of Uttaranchal state. The flux tower at
Haldwani is equipped with CSAT sonic anemometer, LI-7000
closed path gas analyzer, radiation and soil thermal sensors.
Measurements are logged at 10 Hz interval using data logger.
Half-hourly CO, flux measurements corresponding to dry
period (18-28 Jan, 2009) and flush stage (April, 2009) were
processed to study the diurnal variation in net ecosystem
exchange and its response to environmental variables. Light-
response curves were derived for quantifying quantum
photosynthetic efficiency. Efficiency worked out to be 0.021
pmol CO, pmol photon! during flush stage. Respiration-
temperature response was also evaluated to derive Qio
coefficients. In order to quantify CO; fluxes over large region,
initial efforts are made to upscale site-specific data using
process based ecosystem models. Figure 3 shows one
representative CO, flux with day time CO, removal with a
daily peak mean of -3 mg/m//s and night time CO; build up due
to respiration alone from the Betul flux tower located in Teak
mixed forest from central India.
15
1
0.5
0
-0.5
[Mgl[mol-1][m-2)
Figure 3: showing CO; flux results from eddy covariance
method from Betul tower, M.P., India.
