4 research outputs found
NDVI and PRI as indicators of diurnal changes in fraction of absorbed photosynthetically active radiation for fallow and selected species of crop plants
Frakcja akumulowanej energii fotosyntetycznie czynnej (fAPARcanopy) jest
ważnym parametrem ekofizjologicznym, stosowanym między innymi do szacowania produkcji
pierwotnej brutto (GPP) ekosystemów. W pracy przedstawiono zależności pomiędzy dobową zmiennością
frakcji akumulowanej energii fotosyntetycznie czynnej a dwoma spektralnymi wskaźnikami
roślinności – znormalizowanym różnicowym wskaźnikiem wegetacji (ang. Normalized Difference
Vegetation Index, NDVI) i wskaźnikiem odbicia fotochemicznego (ang. Photochemical Reflectance
Index, PRI). Pomiary wykonano 28 maja 2012 r. na poletkach eksperymentalnych z uprawami
jęczmienia jarego, żyta ozimego i pszenicy ozimej oraz na poletku wieloletniego odłogu. Pomiary
padającego, przepuszczonego i odbitego promieniowania w zakresie PAR (potrzebne do obliczenia
fAPARcanopy) wykonano z wykorzystaniem systemu pomiarowego firmy Delta-T (Delta-T Devices,
Cambridge, UK). Potrzebne do obliczenia NDVI i PRI pomiary promieniowania padającego i odbitego
o długościach fali 530, 570, 670 i 849 nm wykonano używając dwóch czterokanałowych czujników
SKR1850 (SKYE Instruments Ltd., Llandrindod Wells, UK), zamontowanych w pozycji zenit – nadir
na przenośnym urządzeniu SpectroSense2+. Z zaprezentowanych danych wynika, że NDVI stanowi
znacznie lepszy niż PRI spektralny wskaźnik dobowej zmienności fAPARcanopy roślin uprawnych.
Uzyskane wyniki świadczą o tym, że fAPARcanopy nie jest jedynym czynnikiem kształtującym zmienne
wartości wskaźników NDVI i PRI w cyklu dobowym.fAPARcanopy is an important ecophysiological parameter, widely used for Gross Primary
Production estimation. The paper presents the effect of diurnal changes in fAPARcanopy on two
spectral vegetation indices – NDVI and PRI. Measurements were made on 28th of May, 2012, for 4
measurement plots (fallow, spring barley, winter rye, winter wheat). Measurements of incident, transmitted
and reflected photosynthetically active radiation (used for fAPARcanopy calculation) were performed
using Delta-T measurements system (Delta-T Devices, Cambridge, UK). Measurements of
incident and reflected radiation at 530, 570, 670 and 849 nm were used for NDVI and PRI calculation.
They were performed using two SKR1850 sensors (SKYE Instruments Ltd., Llandrindod Wells, UK)
mounted in zenith-nadir position on the mobile Spectrosense 2+ device. Presented data showed that
NDVI was much better than PRI spectral indicator of diurnal variability of fAPARcanopy of crop plants.
Results indicated that the fraction of absorbed photosyntetically active radiation (although its impact
was noticeable) was not the only factor affecting diurnal changes in NDVI and PRI values
NDVI and PRI as indicators of diurnal changes in fraction of absorbed photosynthetically active radiation for fallow and selected species of crop plants
fAPARcanopy is an important ecophysiological parameter, widely used for Gross Primary Production estimation. The paper presents the effect of diurnal changes in fAPARcanopy on two spectral vegetation indices – NDVI and PRI. Measurements were made on 28th of May, 2012, for 4 measurement plots (fallow, spring barley, winter rye, winter wheat). Measurements of incident, transmitted and reflected photosynthetically active radiation (used for fAPARcanopy calculation) were performed using Delta-T measurements system (Delta-T Devices, Cambridge, UK). Measurements of incident and reflected radiation at 530, 570, 670 and 849 nm were used for NDVI and PRI calculation. They were performed using two SKR1850 sensors (SKYE Instruments Ltd., Llandrindod Wells, UK) mounted in zenith-nadir position on the mobile Spectrosense 2+ device. Presented data showed that NDVI was much better than PRI spectral indicator of diurnal variability of fAPARcanopy of crop plants. Results indicated that the fraction of absorbed photosyntetically active radiation (although its impact was noticeable) was not the only factor affecting diurnal changes in NDVI and PRI value
The full GHG balance of croplands under seven-year rotation scheme and conventional tillage practices in Poland
Greenhouse gases fluxes were measured with chambers on the selected plots of the experimental arable station of
Poznan University of Life Sciences in Brody (52o26’N, 16o18’E), Poland. This is a long term experiment, where
the same crops are cultivated under the same fertilization treatment schemes (eleven combinations) since 1957.
At the blocks of the full 7-year rotation, there are cultivated in permanent rotation: winter wheat ->winter rye
-> potato ->spring barley -> triticale and alfalfa (till the second year). GHG fluxes have been measured on plots
with the same fertilization level (Nmin-90kg, K2O-120 kg/ha, P2O5-60 kg/ha and Ca), which is very close to the
average amount of mineral fertilization applied in western Poland. No catch crops were cultivated between the
main crops. The soil was classified as Albic Luviosols according to FAO 2006 classification.
CO2 fluxes have been measured monthly since March 2011, while N2O and CH4 fluxes since March 2012
(weekly) and measurements were continued till October 2013. CO2 fluxes were measured with dynamic chambers,
while N2O and CH4 fluxes were measured with both static and dynamic chambers approaches (using
LOSGATOS gas analyser). Carbon net ecosystem exchange (NEE) and ecosystem respiration (Reco) have been
modelled for the entire period based on the measured fluxes (different management treatments were included in
the model), while N2O and CH4 fluxes were linearly interpolated between campaigns.
Taking into account the accumulation periods between 15th of October and 14th of October of the next year the
cumulated NEE was negative only in case of alfalfa, winter rye and winter wheat, reaching in average -3.5 tCO2-C
ha-1 for alfalfa and winter rye fields and around -0.4 tCO2-C ha-1 for winter wheat in seasons 2011-2012 and
2012-2013. While, cumulated NEE for spring crops (potato and spring barley) was positive for the same periods
and reached in average 1.1 tCO2-C ha-1 and 2.5 tCO2-C ha-1 for spring barley and potatoes, respectively. The
fields with spring crops have positive NEE, and hence negative climatic impact, because by more than half of the
year the soil was bared and no catch crops were cultivated between main crops.
For the entire 12-months period the highest N2O emission rates were recorded at plots of winter wheat and
winter rye and reached 2.2 kgN2O-N ha-1 and 2.0 kgN2O-N ha-1, respectively. At plots of alfalfa and potatoes
the emission rates were close to 1.5 kgN2O-N ha-1, while at spring barley plots the emission did not exceed 1.1
kgN2O-N ha-1. At the same time, the yearly CH4 uptake reached from -0.9 kgCH4-C ha-1 at plots of alfalfa, -1.5
kgCH4-C ha-1 at plots of winter wheat to around -1.7 kgCH4-C ha-1 at winter rye, potato and spring barley plots