Yogesh Kant

Biomass and combustion characteristics of secondary mixed deciduous forests in Eastern Ghats of India

Abstract Biomass quantities at three different sites in tropical moist mixed secondary deciduous forests before and after burning have been quantified in the forest patches cleared for shifting cultivation purposes. The main objective of the experiments was to study the spatial variability in the amount of biomass burnt and the contribution of different components viz., bole, branch, and mixed leaf litter in the burning process affecting the combustion factors. Species composition at the three sites varied with respect to each other. The total density of species before burning at the three sites for more than 10xa0cm diameter were found to be 3192 (site 1), 1194 (site 2) and 1444 (site 3) stems/area, respectively. Analysis of the results from girth-class and density relationships suggests that nearly 80% of the stems occurred in the range from 10–40xa0cm girth for site one, 64.2% in 10–55xa0cm girth class for the site two and more than 80% of stems in 10–40xa0cm girth class for the site three, indicating very poor and secondary nature of the forest. The fire intensity is found to be high for site one with 60xa0847xa0kJxa0s −1 xa0m −1 , when compared to 31xa0086 and 42xa0789xa0kJxa0s −1 xa0m −1 for second and third sites, respectively. The values are comparatively higher than the mean value of 2566xa0kJxa0s −1 xa0m −1 reported for savanna fires. The individual combustion completeness suggested that among the different components of biomass, branch material with less than 10xa0cm and upto 5xa0cm dbh contributed to more than 60% of combustion. Mixed leaf litter contributed to about more than 50% of individual combustion completeness at all the sites, with third site having the highest (84%). The contribution of dry biomass material having more than 70xa0cm diameter is found to be very low indicating that most of the trunks were burnt superficially. The overall combustion completeness suggested that mixed leaf litter and branch material contributed to most of the combustion. Of all the three sites, site three had been found to be having highest combustion completeness of about 30.04% when compared to 20.18% and 16.1% for first and second sites, respectively. In the study, comparison of combustion factors for different vegetation types has also been made.

Biomass burning and related trace gas emissions from tropical dry deciduous forests of India: A study using DMSP-OLS data and ground-based measurements

Biomass burning is one of the major sources of trace gas emissions in the atmosphere. In India the major sources of biomass burning include deforestation, shifting cultivation, accidental fires, controlled burning, fire wood burning, burning from agricultural residues and burning due to fire lines. Studies on biomass burning practices gain importance due to increasing anthropogenic activities and increasing rates of deforestation. Satellite data have been widely used over the globe to monitor the rates of deforestation and also with respect to biomass burning studies. But, much of the polar orbiting satellites, due to their repetitive cycle, have limitations in observing such events and in the tropics, due to cloud cover, getting a cloud-free image during the daytime is difficult. In this study we used Defence Meteorological Satellite Program Operational Line Scanner (DMSP-OLS) night-time data to study the biomass burning events over a period of 10 years from 1987 to 1998 for the Eastern Ghats region, covering the northern part of Andhra Pradesh, India. Two ground-based experiments were carried out to quantify the emissions from biomass burning practices. The results of the study with respect to trace gases suggested emission ratios for CO, CH4, NOx and N20 during the burning to be about 12.3%, 1.29%, 0.29% and 0.07% at the first site and 12.5%, 1.59%, 0.29% and 0.05% at the second site, suggesting low inter-fire variability between the sites. The variation has been attributed to the fuel load, vegetation characteristics, site conditions and local meteorological parameters affecting the relative amounts of combustion. Using the DMSP OLS derived areal estimates of active fires, the trace gas emissions released from the biomass burning were quantified. The results suggested the emissions of 8.2 2 10 10 g CO 2, 1.8 2 10 8 g CO, 6.0 2 10 6 g N 2 O, 3.0 2 10 6 g NO x and 1.2 2 10 8 8 g CH 4 during March 1987. The emissions increased to 1.0 2 10 11 g CO 2, 2.3 2 10 g CO, 7.8 2 10 6 g N 2 O, 3.9 2 10 7 g NO x and 1.6 2 10 8 g CH 4, over a period of 10 years. The results of the analysis suggest the possible use of monitoring biomass burning events from DMSP-OLS night-time data.

Studies on aerosol optical depth in biomass burning areas using satellite and ground-based observations

Biomass burning in the tropics is a source of trace gas fluxes and particulate matter. During the last decade, the shifting cultivation practices have been increased in the tropical forest of Eastern Ghats, Andhra Pradesh, India. In order to quantify the fluxes emitted from the biomass burning due to shifting cultivation practices, a field experiment has been conducted on February 16-25, 1999. The present study provides the variation of aerosol optical depth over the shifting cultivation areas of Rampa Revenue Division, Eastern Ghats using a sunphotometer in synchronism with satellite data. Optical depth values increased up to 2.0 during the burning phase and then returned to normal values (0.2-0.5). The atmospheric correction of the satellite data using the optical depth values suggested improvement in the overall contrast of the image and increase in the dynamic range of the normalized difference vegetation index (NDVI) values of various features in the image.

NOx emissions from biomass burning of shifting cultivation areas from tropical deciduous forests of India- estimates from ground-based measurements

Abstract Biomass burning in the tropics is an important source of trace gases. Shifting cultivation in India is one of the major sources of biomass burning activities, during which due to combustion, several trace gases are emitted into the atmosphere. NO x emissions are relatively important as they affect the tropospheric photochemistry. In the present study, an attempt has been made to quantify the NO x emissions from shifting cultivation areas of tropical dry deciduous forests of India, at two sites. Fuel load, fuel characteristics, and nutrients with respect to carbon and nitrogen have been analyzed. Emission ratios have been calculated relative to CO 2 . Results of the study suggested that fuel load ranged from 12–15.3xa0txa0ha −1 . Fire intensity at the first site was 3207xa0kcalxa0s −1 xa0m −1 and 2882xa0kcalxa0s −1 xa0m −1 at the second site. The differences in the fuel moisture were found to be less than 10% at both of the sites. The CO/CO 2 ratio at the two sites did not vary much due to the low variation in moisture content. The carbon and nitrogen loads for the two sites ranged from 5603xa0txa0Cxa0ha −1 to 286xa0txa0Nxa0ha −1 and 6364xa0txa0Cxa0ha −1 and 239xa0Nxa0ha −1 , respectively. Using the relation of estimating the emission factor (EF) for estimating the NO x emissions (EF (NO x )=−1.5+3.9 nf , where, (r=0.95) EF(NO x ) is the emission factor for NO x in grams of nitrogen per kilogram of dry matter (gxa0Nxa0kg −1 xa0dm) burned and `nf’ is the percent of nitrogen bound within the plant matter, for tropical deciduous forests, suggests an emission rate of 7.0 (gxa0Nxa0kg −1 xa0dm) for the first site, and 4.7 (gxa0Nxa0kg −1 xa0dm) for the second site when compared to actual measured emission rates of 4.8 (gxa0Nxa0kg −1 xa0dm) for the first site and 3.5 (gxa0Nxa0kg −1 xa0dm) for the second site, indicating a higher estimate for the global regression relation used by Dignon and Penner. The emission factors computed from nitrogen content of the fuel material for tropical dry deciduous forests are nearer to the relation obtained for African Savanna fires. Comparison of the measured emission factors for the tropical deciduous forests with other ecosystems has been made in the paper.

CH4 emissions from biomass burning of shifting cultivation areas of tropical deciduous forests – experimental results from ground-based measurements

Abstract Context Abstract : Tropical deciduous fires from shifting cultivation process in India are characterized by the highly differential nature of fire behavior due to fragmented burning patterns. Our study from ground-based experiments from biomass burning of tropical deciduous forest fires suggests smoldering combustion as the dominating process during biomass burning which leads to evolution of more incompletely oxidized products such as Methane when compared to other ecosystems such as Savannas. In the study, we report emission ratios and emission factors for methane from biomass burning of tropical deciduous forests. As tropical deciduous forests in India cover more than 50% of overall forests, the emission factors obtained in the present study can be used widely for methane emission estimation from forest biomass burning studies in other parts of India and in modeling studies of Methane from forest biomass burning in India. Main Abstract : Biomass burning is an important source of trace gas emissions to the atmosphere. Methane emitted from the biomass burning contributes to the atmospheric greenhouse effect and is sufficiently long-lived to enter the stratosphere and take part in the stratospheric ozone cycles. In India, though CH 4 emissions from the different sources such as rice paddy fields and domestic animals have been well studied, there are relatively no field-based studies with respect to CH 4 emissions from biomass burning. In the present study, we report for the first time, the CH 4 emissions from biomass burning of tropical deciduous forests cleared for shifting cultivation purposes. Trace gas emissions from the biomass burning plumes have been collected through grab sampling in canisters as well as from online measurements through instruments. Site characteristics with respect to species composition, amount of biomass burnt and relative amounts of combustion, viz., flaming, mixed and smoldering have been determined. Modified combustion efficiency has been used to differentiate relative amounts of combustion. Emission ratios were calculated with respect to CO 2 and emission factors based on the amount of biomass consumed. Results of the study with respect to biomass estimations prior to burning suggested values of 12–14 t ha −1 at the first site and 13.5–15.3 t ha −1 at the second site. The mean modified combustion efficiencies during flaming, mixed and smoldering combustion phases for the first site were found to be 95.7%, 91.1% and 74.4% and 95.31%, 90.63% and 72.89%, respectively, for the second site. The average biomass consumed during the fire ranged from 4.7 t ha −1 (site 1) to 3.4 t ha −1 (site 2), indicating low amount of biomass burnt during the first phase of burning in shifting cultivation areas. Results suggested the CH 4 emission ratios of 1.29% at the first site and 1.59% at the second site. The CH 4 emission ratios obtained in the present study are closer to the most accepted estimates of 1.2±0.5% obtained for tropical forests elsewhere. Using the emission ratios obtained in the study and estimating the amount of methane emissions from biomass burning suggests that nearly 0.99 Tg of methane is emitted annually from shifting cultivation process in India. Also, in the study, a detailed comparison of emission ratios and emission factors of CH 4 has been made.

Studies on land surface temperature over heterogeneous areas using AVHRR data

The study addresses the use of the split-window method in tropical regions for estimation of surface temperature over heterogeneous surfaces from satellite sensor data. An attempt has been made to derive emissivity in the thermal channels using the NDVI in conjunction with fractional vegetation cover at pixel level. The estimated surface temperature values are compared with the in situ data over the region and are found to be within error limits of +/- 1.8°C. The utility of fractional vegetation cover in controlling surface temperature has been studied for the selected features over the area. The results suggest the utility of emissivity estimated from the NDVI in land surface temperature estimation.

Algorithm for detection of active fire zones using NOAA AVHRR data

Abstract Forest fires in tropical countries have become one of the important sources of Green House Gases and cause damage to the forest ecosystems. Information relating to the extent and location of active fire zones needs immediate attention to facilitate effective management and mitigation of forest fires. The spectral intervals that are most suitable for the detection of forest fires are 3.5–4.2 and 4.4–5.0 μm. The maximum thermal emission of fires is localized using middle infrared and thermal infrared bands for automatic recognition of fire active zones. The algorithm considers the thresholds for middle infrared on the basis of channel saturation to discriminate the fire zones from background warm surface and thermal infrared (10.3–11.3 μm) to ensure it to be free from cloud and water bodies. Advanced Very High Resolution Radiometer (AVHRR) data of 1 km resolution have been taken and we apply a spatial technique using background information to dynamically define thresholds appropriate for identifying fire pixels. The study suggests that satellite data provide a unique tool to detect and monitor active fire distribution.

CENTURY ecosystem model application for quantifying vegetation dynamics in shifting cultivation areas: A case study from Rampa Forests, Eastern Ghats (India)

In India, slash and burn agriculture is one of the major factors contributing to deforestation, especially in the hilly north-eastern region and Eastern Ghats. Studies on vegetation dynamics associated with slash and burn agricultural practices have been intensively studied in the north-eastern part of India. These have covered semi-evergreen/evergreen vegetation, but similar studies on tropical mixed dry deciduous ecosystems are not as common. In the present study, we used the century ecosystem model to study vegetation dynamics in shifting cultivation areas on the mixed dry deciduous forests covering the Eastern Ghats of India. The site-specific parameters, temperature, precipitation, biomass and nutrient pools were used, and, by collecting information from local management practices, a 12-year shifting cultivation cycle during a 70-year period from 1960 to 2030 was simulated. century estimated a total loss of 239 tonnes carbon (tC) in soil organic matter over the simulation period, and the total nitrogen content of the soil organic matter showed an initial increase followed by a decline (344.3 g m2 during 1960 to less than 318.3 g m2 during 2030). century estimated that 66 tC ha−1 would be lost from the forest system, reducing the initial forest system carbon level from 118.5 tC ha−1. An increase in productivity from 0.49 tC ha−1 during 1960 to 1.2 tC ha−1 during the initial forest slash and burn in 1962 was observed, but thereafter productivity declined to 0.7 tC ha−1 during the year 2030. Results obtained in other studies of similar types of agricultural practices are also reviewed.

Ground-based method for measuring thermal infrared effective emissivities: Implications and perspectives on the measurement of land surface temperature from satellite data

Thermal infrared emissivity is an important parameter for surface characterization and for determining surface temperature. The field-based measurements for ground and vegetation emissivities in 8-14 w m waveband were performed with an emissivity box. A theoretical analysis was carried out using the box and a correcting factor has been determined. The average value for thermal band emissivity of the exposed bare soil was found to be around 0.909; the average value measured for most of the varieties of vegetation present were in the range of 0.980-0.985. A theoretical model is used for obtaining effective emissivity in the 8-14 w m region from Advanced Very High Resolution Radiometer (AVHRR) data considering the proportion of vegetation cover in a pixel and the field-measured emissivity values. The error of the methodology is found to be within 1.5%. Narrow band emissivities for AVHRR channels 4 and 5 have been derived from the emissivity values in the 8-14 w m waveband. The surface temperature has been derived from AVHRR data using a split-window algorithm as a function of emissivities derived in narrow bands. The split-window algorithm accounted for absorption effects of the atmosphere by incorporating the water vapour concentration measured in the campaign. A good agreement was obtained between the satellite-derived surface temperature and the in situ observations. The result suggest that the methodology allows us to derive land surface temperature with an accuracy better than 1.5° C provided the surface emissivity is known. The paper describes the field-based emissivity measurement and approach for deriving surface temperature over land surface.

Regional scale evapotranspiration estimation using satellite derived albedo and surface temperature

In the studies reteted to surface energy balance, satellite data provides important inputs for estimating regional surface albedo and evapotranspiration. The paper describes the use of satellite data in determining the surface emissivity over heterogeneous a’reas by taking Normalized Difference Vegetation Index (NDVI) as modulating parameter at pixel resolution. The estimated emissivity values have been used to find the surface temperature at the pixel scale. Landsat-TM-visible, NIR, TIR bands data and some ground meteorological data have been used in an energy balance model for estimating surface albedo and evapotranspiration. The ET values derived from the model are in good agreement with the values obtained with. ‘CENTURY MODEL’ and ground observations over the area, suggesting the possible use of this approach fot regional scale studies on evapotranspiration.