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> On 
local characteristics. 
(p. To evaluate net primary 
productivity (NPP) to provide 
spatial information that can be 
used for land use planning 
usingc more recently developed 
and sophisticated oProduction 
Efficiency Model (PEM). 
PEM: |whichscan^adsorwuse remote- 
ly sensed data as inputs, has 
been successfully used for 
estimation of global NPP 
(Prince: ando Goward: 1995),::but 
no separate estimates for 
agricultural productivity has 
yet been attempted\on auregion- 
al and global'*scale. Thersfore, 
agricultural productivity 
estimation was takens up for 
india, ones of 'the»agricultural- 
ly dominant country, using PEM. 
2. Theory 
Productivity is the rate of 
atmospheric carbon uptake by 
vegetation through the process 
of: photosynthesis. Built up: of 
productivity is a complex 
phenomenon which is a 
culmination of many temporal 
plant processes. Recent methods 
to evaluate NPP involves 
decomposition of productivity 
into independent parameters 
such as Incoming solar 
radiation, radiation ‘absorption 
efficiency and conversion 
efficiency of absorbed 
radiation into. organici; matter 
(Kumar and Monteith, 1981). The 
models developed in these 
studies are an advancement over 
the statistical models properly 
accounting. for various steps -in 
the productivity built up 
process. 
Goward et.al.(1985) showed that 
vegetation indices, such as 
Normalized Difference Vegeta- 
thon Index 5 (NDVI;) are related 
to net primary production (NPP, 
g m year ) Monteith x (1977) 
Suggested that + NPP: under non: 
Stressed conditions is linearly 
related to the amount of photo- 
synthetically active ckpadiat ion 
(PAR, MJ mi"). uthat:is absorbed 
by green foliage (APAR, MJ m 
- Further, Kumar. and. Monteith 
(1981) showed how the fraction 
Of PAR absorbed (fAPAR) relates 
to the ratio of red reflectance 
(RJ to near infrared (NIR).. 
Asrar et.al. (1984) subsequent - 
iy reiated o the - NDVI -tó- the 
fAPAR; hence NDVI may be used 
to estimate NPP at global scale 
by the relationship: 
NPP-ceX(APAR)-eXZ (NDVI*IPAR) 
where E(APAR) is the annual sum 
of APAR, € is the PAR 
conversion: efficiency Ag MJ.) 
299 
and /IPAR£Mis. the/rincident PAR. 
This iis the simplest formo of 
the Production Efficiency Model 
(PEM). 
Eck and Dye (1991)mdescribed-.a 
simple, physically based, 
satellite remote sensing method 
for; estimating -1PAR that: uses 
ultraviolet (UV) reflectivity 
data from the Nimbus Total 
Ozone Mapping Spectrometer 
(TOMS) . Subsequently, Dye 
(1995) generated a time series 
global monthly IPAR »datairset 
using the same technigue, which 
Lis quite. -useful/sfor. :regionali 
and global productivity studies 
(Prince and Goward, 1995). Dye 
andi Goward. (1993) also. created 
a global APAR image using 
Spectral reflectance measure - 
ments from the NOAA-7 AVHRR and 
TOMS data. 
One.ofcthe major problemi in the 
NPPirestimations is: I the finding 
Of representative values ‘of € 
for various vegetation types as 
ith -changes:o withswthe »stype | of 
vegetation, temperature, water 
availability and metabolic type 
ofi the: planc iC or; € type). 
Princesd9945'"and^Ruimy *et..2$al. 
(1994) Searched through the 
literature and listed € values 
for various vegetation and 
ecosystem types. Hunt (1994) 
Suggested that global estimates 
of NPP based on vegetation 
indices should include a clas- 
sification among established 
forest, young: forest rand non- 
forest ecosystems to account 
for differences in e. 
3. DATA 
3.1 Satellite data 
3.1.1 NDVI data: NASA/NOAA 
Pathfinder AVHRR Land (PAL) 10 
day composited -NDVI data set 
for =the year 21987, 1988, - ‘ana 
1989 was procured from the 
Goddard Distributed Active 
Archive Center (DAACh, USA. :To 
generate » composited data: set, 
107 consecutive days of data are 
combined, taking the observa- 
tion- for each 8:km bin from the 
data with the fewest: clouds and 
atmospheric contaminants as 
identified by the highest NDVI 
value. There: are three; compo- 
sites: persmonthh foro each: year 
of datash Thet compositing tech- 
nique faeirdliy- removes the cloud 
contamination from the data to 
use in climatic modeling stud- 
ies: (Agbw and James, 31994). The 
data” is ‘available on. Goode*'s 
Equal Area Projection. 
data: Global IPAR 
generated by Dye 
using UV reflectivity 
351.2 IPAR 
data set 
(1995) 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996