@article {KNZ00276, title = {Net carbon dioxide exchange in canopies of burned and unburned tallgrass prairie}, journal = {Theoretical and Applied Climatology}, volume = {42}, year = {1990}, pages = {237 -244}, abstract = {

Net carbon dioxide exchange (NCE) rates were measured in a tallgrass prairie, a grassland with high productivity, to determine photosynthetic rates of the canopy. Canopy measurements were made in large, plexiglass chambers (1.21 m long; 0.91 m wide; 1.40 m tall) placed on burned and unburned areas of the prairie. The NCE rates of the canopy were compared with those of individual leaves of Andropogon gerardii Vitman (big bluestem). In addition, CO2 flux from the soil was quantified and compared with net photosynthetic flux. The canopy NCE rates were generally lower than those made on individual leaves. In mid-summer (11 July 1987), the maximum canopy NCE rates were 55\% and 64\% of those measured on individual leaves in burned and unburned treatments, respectively. Canopy NCE rates were lower than individual-leaf NCE rates for two reasons. First, the individual-leaf measurements were made on young, unshaded, healthy leaves, while the canopy measurements were made on all types of leaves including senescing, shaded, and damaged leaves. Second, soil CO2 flux into the chambers lowered NCE values. The CO2 flux from the soil ranged from 7.2\% to 28.4\% of the total NCE. One needs to add soil CO2 flux rates to the measured canopy NCE rates to obtain canopy NCE rates closer to individual-leaf NCE rates. Soil CO2 flux decreased when conditions became dry, reaching a low of 0.06mg CO2m-2s-1, but increased after rain to 0.16mg CO2m-2s-1. Also, after rain, when plants were well watered, they were not light saturated at 1900{\ae}Em-2s-1. The NCE rates on the burned treatment were either higher or similar to those on the unburned treatment. For example, on 11 July 1987, NCE rates were higher on the burned treatment (0.66 mg CO2m-2s-1) compared to the unburned treatment (0.47 mg CO2m-2s-1). During the rest of July and August, the rates of the two treatments were not significantly different. but in September and October, the NCE rates were again higher on the burned treatment compared to the unburned treatment. The results indicated that canopy NCE rates may be more indicative of the productivity of the prairie than individual-leaf measurements made only on young, highly productive leaves

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1007/BF00865984}, author = {Gale, W.J. and Kirkham, M.B. and Kanemasu, E.T. and Owensby, C.E.} } @article {KNZ00297, title = {Separability of soils in a tallgrass prairie using SPOT and DEM Data}, journal = {Remote Sensing of the Environment}, volume = {32}, year = {1990}, pages = {10 -17}, abstract = {

A sufficient transformation technique is important in using computer-aided soil pattern recognition to interpret soils in soil surveys. This study was conducted using the Systeme Probatoire d\&$\#$39;Observation de la Terre (SPOT) satellite images and Digital Elevation Model (DEM) data to seperate five major sils in a tallgrass prairie near Manhattan, Kansas. The high resolution SPOT satellite im;ages were integrated with DEM data. the soils were sampled and classified using conventional soil survey procedures to extract the important soil features from SPOT and DEM data. A pairwise transformed divergence analysis was also conducted to evaluate the several aanonical variables in order to sufficiently separate the soils. Consequently, two canonical variables derived from training samples were selected. Our results suggest that canonically transformed data were superior to combined SPOT and DEM data. High resolution SPOT images and DEM data can be used to aid secondd- order soil surveys in grasslands

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1016/0034-4257(90)90027-J}, author = {Su, H. and Kanemasu, E.T. and Ransom, M.D. and Yang, S.} } @article {KNZ00256, title = {Detecting soil information on a native prairie using Landsat TM and SPOT satellite data}, journal = {Soil Science Society of America Journal}, volume = {53}, year = {1989}, pages = {1479 -1483}, abstract = {

Computer pattern recoginiton techniques were used to discriminate soil information from the Landsat Thematic Mapper (TM) and the French Systeme Probatoire d\&$\#$39;Observation de le Terre (SPOT) satellite data on a native prairie near Manahttan, KS. Digital Elevation Model (DEM) data were merged to Landsat TM and SPOT data to delineate soil mapping units within the study area. Soil mapping units from a conventional soil survey were compared with a classified soil spectral map obtained from Landsat TM or SPOT, and DEM derived elevation, slope, and aspect data, using an overall accuracy assessment. The overall accuracy of soil spectral classesfrom TM and SPOT data were merged. A higher average accuracy for soil mapping units was obtained with a low frequency filtering transformation of the data. For Landsat TM data, Band 5 (middle infrared, 1.55-1.75 {\ae}m) was most useful for soil information extraction, and a higher overall accuracy was obtained in the dormant season compared with the accuracy in the growing season. The overall accuracy (about 57\%) from SPOT data was slightly higher than the accuracy (about 53\%) from Landsat TM at a similar wavelength range. Our results indicate that high resolution Landsat TM and SPOT satellite data can be used to aid second-order soil surveys in areas where the dominant land use is rangeland

}, keywords = {LTER-KNZ}, doi = {10.2136/sssaj1989.03615995005300050030x}, author = {Su, H. and Ransom, M.D. and Kanemasu, E.T.} } @article {KNZ00214, title = {Measuring and modeling spectral characteristics of a tallgrass prairie}, journal = {Remote Sensing of the Environment}, volume = {27}, year = {1989}, pages = {143 -155}, abstract = {

This study was conducted to evaluate the diurnal and seasonal, spectral reflectance characteristics of burned and unburned areas of a tallgrass prairie, based on field measurements and models of radiation transport in plant canopies. Burning of the senescent vegetation, resulting from the previous years\&$\#$39; growth, is a common management practice, which results in improved productivity and affects the succession of grass species. The burned and unburned grass canopies showed distinctly different, diurnal and seasonal, spectral reflectance characteristics in the visible and infrared regions of the spectrum. These were attributed to the differences in development of the two plant canopies and the azimuthal differences in sensor-sun-canopy positions during field measurements of spectral reflectance. The radiation transfer model properly simulated the diurnal spectral behavior of the two canopies. The simulated, seasonal, spectral reflectance values for the unburned grass canopy were greater than the measured ones, because of limitations in proper representation of the layer of senescent vegetation in the model

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1016/0034-4257(89)90014-X}, author = {Asrar, G.A. and Myneni, R.B. and Li, Y. and Kanemasu, E.T.} } @proceedings {KNZ00159, title = {Airborne multispectral observations over burned and unburned prairies}, year = {1987}, pages = {203 -207}, address = {Ann Arbor, MI}, abstract = {

One of the ongoing studies at the Konza Prairie Natural Area (KPNA) in central Kansas is that of determining the effects periodic burning has on the native grassland ecosystem. In this study, watersheds are burned at intervals from one year to ten years or not at all. The Evapotransiration Laboratory at Kansas State University has been studying the multispectral response of burned and unburned watersheds using truck mounted raiometers and microwave scatterometers since 1983. In June 1985, there was a series of 5 flights with the NASA C-130 aircraft over the KPNA. On board the aircraft was the NS001 multispectral scanner, also known as the thematic mapper simulator. It has 7 visible and near IR channels and a thermal IR channels, whose spectral bands were chosen to simulate the thematic mapper on Landsat\&$\#$39;s 4 and 5. The 21-cm Pushbroom Microwave Radiometer (PBMR) was also on board the aircraft for soil and moisture observations. In addition several L- Band SAR images from the NASA CV-990 aircraft were obtained during this period. The spectral differences between the burned and unburned watersheds were clearly observable in all spectral bands including the thermal IR and the microwave. The normalized difference vegetation index (NDVI) using TM bands 3 and 4 was calculated. Values of less than 0.5 were obtained for the unburned watersheds which contained a mixture of senescent and green vegetaion. The NDVI values for the burned watersheds which contained only green vegetation were greater than 0.6. In the thermal IR, 3 to 4 degree Celsius temperature differences between the two treatments were observed at about 2:00 p.m. LST with the burned watersheds being cooler. Large differences between the two treatments were observed in the microwave emissivities derived from the PBMR data. These are attributed to the build-up of a layer of senescent vegetation on the soil surface in the unburned and ungrazed watersheds

}, keywords = {LTER-KNZ}, author = {Schmugge, T.J. and Kanemasu, E.T. and Asrar, G.A.} } @article {KNZ00130, title = {Assessing grassland biophysical characteristics from spectral measurements}, journal = {Remote Sensing of the Environment}, volume = {20}, year = {1986}, pages = {141 -152}, abstract = {

Remote sensing offers a potential alternative to tedious hand sampling as a means of monitoring vegetation condition and estimating productivity over large areas of grasslands. This sutdy was conducted to assess the use of spectral reflectance measurements in estimating grass canopy leaf area index (LAI) and total above ground green phytomass. Spectral reflectance measurements were made on a tallgrass prairie during 1983 and 1984 with two multiband radiometers. Green leaf-area index and dry matter accumulations (green above-ground phytomass) were measured on the area monitored by the radiometer. Three indices-near infrared to red ratio, greenness, and normalized difference-were computed from spectral reflectance data. The direct relationships between these special reflectance indices and grass biophysical parameters (LAI and phytomass) were site-dependent and year-specific. Indirect methods of estimating LAI and phytomass from estimates of absorbed, phytosynthetically active radiation, based on measurements of grass canopy spectral reflectance, were found to be more consistent across treatments for the two years of this study

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1016/0034-4257(86)90019-2}, author = {Weiser, R.L. and Asrar, G.A. and Miller, G.P. and Kanemasu, E.T.} } @article {KNZ00110, title = {Distinguishing among tallgrass prairie cover types from measurements of multispectral reflectance}, journal = {Remote Sensing of the Environment}, volume = {19}, year = {1986}, pages = {159 -169}, abstract = {

The heterogeneity in surface cover caused by management practices or natural events complicates monitoring the conditions of grasslands and asseessing their productivity by remote sensing techniques. Statistical procedures were sought that would allow different grassland surface cover types (bare soil,senescent vegetation, and green vegetation) to be distinguished by using measurements of grassland multispectral reflectance. Two procedures, discriminant functions and canonical discriminant analysis, were found suitable for achieving this objective. Linear classification functions and canonical variables were derived, which distinguish between the three cover types. A comparison between two sensor systems, a Barnes multiband radiometer and an Exotech radiometer that simulates the Landsatthematic mapper (TM) and multispectral scanner (MSS) bands, respectively, showed that the separability among the three cover types was substantially improved by the additional and improved spectral features of the Barnes radiometer

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1016/0034-4257(86)90069-6}, author = {Asrar, G.A. and Weiser, R.L. and Johnson, D.E. and Kanemasu, E.T. and Killeen, J.M.} } @article {KNZ00109, title = {Light interception and leaf area estimates from measurements of grass canopy reflectance}, journal = {IEEE Transactions of Geoscience and Remote Sensing}, volume = {GE-24}, year = {1986}, pages = {76 -82}, abstract = {

Grassland is a major component of the Earth\&$\#$39;s available land. The vast area and remoteness of this ecosystem makes it difficult to assess its condition and monitor productivity by traditional methods. Remote sensing potentially offers a rapid nondestructive approach for monitoring such ecosystems. A study was carried out in a tallgrass prairie site near Manhattan, Kansas, during the 1983 and 1984 seasons to investigate the feasibility of estimating light interception and green leaf area index (LAI) from measurements of canopy multispectral reflectance. Greenness (Gn) index was found to be strongly correlated with intercepted photosynthetically active radiation (PAR). Two methods, a direct regression (RGR) and an indirect approach (IND), were used to estimate LAI form Gn index. The LAI values estimated by RGR method were consistently lower than the measured ones; however, good agreement was obtained between the LAI values estimated by IND method and the measured LAI. This suggests that Gn transformation of canopy spectral reflectance is more closely related to the fraction of intercepted PAR by green foliage than the quantity of green LAI

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1109/TGRS.1986.289590}, author = {Asrar, G.A. and Kanemasu, E.T. and Miller, G.P. and Weiser, R.L.} }