@inbook {KNZ001759,
	title = {Phenologies of North American Grasslands and Grasses},
	booktitle = {Phenology: An Integrative Environmental Science, 2e},
	year = {2013},
	pages = {197-210},
	publisher = {Springer Netherlands},
	organization = {Springer Netherlands},
	chapter = {11},
	abstract = {<p>Inquiry into the phenologies of grasslands and grasses in North America has progressed substantially in the past decade. Four themes of the recent phenological research are surveyed: (1) the role of exotic and invasive species in affecting grasslands phenology; (2) the role of water and belowground dynamics on phenologies; (3) how experimental manipulations of grasslands have affected constitutive phenologies; and (4) advances in the remote sensing of grasslands. The phyllochron concept used in ontogenetic studies of grass species is discussed in light of grasslands phenology and its link between daylength and thermal time</p>},
	keywords = {LTER-KNZ},
	doi = {10.1007/978-94-007-6925-0_11},
	url = {https://link.springer.com/chapter/10.1007\%2F978-94-007-6925-0_11},
	author = {Henebry, G.M.},
	editor = {MD Schwartz}
}
@article {KNZ001186,
	title = {Tracking the rhythm of the seasons in the face of global change: phenological research in the 21st century},
	journal = {Frontiers in Ecology and the Environment},
	volume = {7},
	year = {2009},
	pages = {253 -260},
	abstract = {<p>Phenology is the study of recurring life-cycle events, classic examples being the flowering of plants and animal migration. Phenological responses are increasingly relevant for addressing applied environmental issues. Yet, challenges remain with respect to spanning scales of observation, integrating observations across taxa, and modeling phenological sequences to enable ecological forecasts in light of future climate change. Recent advances that are helping to address these questions include refined landscape-scale phenology estimates from satellite data, advanced, instrument-based approaches for field measurements, and new cyberinfrastructure for archiving and distribution of products. These breakthroughs are improving our understanding in diverse areas, including modeling land-surface exchange, evaluating climate\&ndash;phenology relationships, and making land-management decisions.</p>},
	keywords = {LTER-KNZ},
	doi = {10.1890/070217},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/070217},
	author = {Morisette, J.T. and Richardson, A.D. and Alan K. Knapp and Fisher, J.I. and Graham, E.A. and Abatzoglou, J. and Wilson, B.E. and Breshears, D.D. and Henebry, G.M. and Hanes, J.M. and Liang, L.}
}
@article {KNZ00906,
	title = {The effect of solar zenith angle and sensor view angle on observed patterns of spatial structure in tallgrass prairie},
	journal = {IEEE Transactions on Geoscience and Remote Sensing},
	volume = {42},
	year = {2004},
	pages = {154 -165},
	abstract = {While it has long been recognized that the anisotropic reflectance properties of a natural surface affect the intensity and spectral distribution of radiance received by a remote sensing instrument, the effects of canopy reflectance geometry on the observed spatial structure of canopy reflectance have not adequately been evaluated. In this paper, near-surface spectrometers were used as part of two experiments to evaluate the systematic variations in the sun-target-sensor geometry on semivariogram metrics (range, sill+nugget variance) summarizing the spatial structure observed in a tallgrass prairie canopy. In the first experiment, reflectance measurements and normalized difference vegetation index (NDVI) values were collected at five sensor viewing angles (-50{\textdegree}, -25{\textdegree}, 0{\textdegree}, 25{\textdegree}, and 50{\textdegree}) from six measurement grids representing three burn treatments and two slope/aspect situations. In the second experiment, data were collected at 2-h intervals, beginning at ≈0800 LST from the same grids with the radiometer at nadir, allowing the spatial structure of reflectance and NDVI to be observed under naturally changing illumination. Results of the geostatistical analysis show that both the range and sill+nugget variance values change with viewing angle. These effects were consistent across all treatments and slope/aspect combinations. However, when viewed from nadir, the sill+nugget variance values of the canopy changed with solar illumination angle and the range values remained nearly constant. These relationships were also observed across all treatments and slope/aspect combinations. The results suggest that sill+nugget values for the same surface may not be directly comparable if not acquired under very similar view angle and illumination conditions. Range values are comparable if the nadir view is used, but not under off-nadir viewing conditions. The implications of these findings point to the need for caution in interpreting spatial structure derived from close-range radiometry or from satellite/aircraft instruments with cross-track or off-nadir pointing capabilities, and in the comparison of images acquired under varying illumination conditions.},
	keywords = {LTER-KNZ},
	doi = {10.1109/TGRS.2003.815674},
	author = {Goodin, D.G. and Gao, J. and Henebry, G.M.}
}
@inbook {KNZ00836,
	title = {Grasslands of the North American Great Plains},
	booktitle = {Phenology: An Integrative Environmental Science},
	year = {2003},
	pages = {157 -174},
	publisher = {Kluwer},
	organization = {Kluwer},
	address = {New York},
	abstract = {The study of appearances of growth, development, and senescence in grassland communities is not an enterprise commonly pursued. Phenology of mid-latitude grasslands is, nevertheless, too large and diverse a collection of phenomena to cover within a single chapter, as it ought to embrace at once the vast Kazakh steppe, the chalk grasslands of southern England, and myriad other grassy landscapes. Thus, the view here shall be on the grasslands of the North American Great Plains, with particular reference to the tallgrass prairie as a type model.},
	keywords = {LTER-KNZ, Anthesis, Great Plains, tallgrass prairie, transient maxima hypothesis},
	url = {http://link.springer.com/chapter/10.1007/978-94-007-0632-3_11},
	author = {Henebry, G.M.},
	editor = {Schwartz, M.D.}
}
@article {KNZ00834,
	title = {The effect of rescaling on fine spatial resolution NDVI data: a test using multi-resolution aircraft data},
	journal = {International Journal of Remote Sensing},
	volume = {23},
	year = {2002},
	pages = {3865 -3871},
	abstract = {Simulation studies have suggested that pixel aggregation can rescale accurately both Normal Difference Vegetation Index (NDVI) data and fields of biogeophysical values inferred from NDVI. There is, however, a dearth of empirical tests of this hypothesis. This study uses nested NDVI observations acquired from an aircraft-mounted digital camera to assess the spatial properties of measured and rescaled image data. Imagery was collected at four altitudes, yielding spatial resolutions varying from 0.625 m to 3.125 m. The common area from these four images was extracted. The finest spatial resolution image was then rescaled by aggregating pixels to synthesize three rescaled images matching the spatial resolution of the measured images. The spatial properties of these measured and rescaled images were compared, using metrics derived from the variogram. Results demonstrate that the spatial patterns of rescaled data do not correspond to those of the directly observed data. The results suggest that rescaling by averaging blocks of pixels may not adequately preserve spatial properties of very high spatial resolution images and consequent inferred biogeophysical fields.},
	keywords = {LTER-KNZ},
	doi = {10.1080/01431160210122303},
	author = {Goodin, D.G. and Henebry, G.M.}
}
@inbook {KNZ00626,
	title = {A landscape perspective of patterns and processes in tallgrass prairie},
	booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie},
	year = {1998},
	pages = {265 -279},
	publisher = {Oxford University Press},
	organization = {Oxford University Press},
	address = {New York},
	keywords = {LTER-KNZ, tallgrass prairie},
	author = {J. M. Briggs and Nellis, M.D. and Turner, C.L. and Henebry, G.M. and Su, H.},
	editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins}
}
@article {KNZ00641,
	title = {Seasonality of finely-resolved spatial structure of NDVI and its component reflectances in tallgrass prairie},
	journal = {International Journal of Remote Sensing},
	volume = {19},
	year = {1998},
	pages = {3213 -3220},
	abstract = {Grass canopies exhibit distinct seasonality in reflectance and spatial patterns in reflectance result from landscape heterogeneity. To investigate the spatial structure of NDVI and its two component reflectances at fine resolution in burned and unburned tallgrass prairie, we use range and relative nugget effect two indicators of spatial structure derived from semivariograms. Results show that spatial dependence of the three spectral measures are similar in the early season when the litter layer has been removed by burning and again in the later season when the canopy is senescent. However, as the canopy develops, the spatial dependence of NDVI deviates from that of its component reflectances. In the unburned canopy, red reflectance appears to strongly influence the spatial pattern of NDVI. In the burned canopy, neither component reflectance strictly determines the spatial pattern of NDVI. Maximum divergence in spatial pattern between NDVI and its components coincides with minimum available moisture, suggesting a relation between moisture stress and spatio-spectral heterogeneity.},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.1080/014311698214280},
	author = {Goodin, D.G. and Henebry, G.M.}
}
@proceedings {KNZ00835,
	title = {Advantages of principal components analysis for land cover segmentation from SAR image series},
	year = {1997},
	pages = {175 -178},
	publisher = {ESA},
	address = {Noordwijk, The Netherlands},
	keywords = {LTER-KNZ},
	url = {http://earth.esa.int/symposia/papers/henebry3/index.html},
	author = {Henebry, G.M.}
}
@article {KNZ00581,
	title = {Spatial and temporal patterns of vegetation in the Flint Hills},
	journal = {Transactions Kansas Academy of Science},
	volume = {100},
	year = {1997},
	pages = {10 -20},
	abstract = {In tallgrass prairie, complex interactions among multiple limiting resources in combination with a variety of land use practices can lead to a heterogeneous landscape. Remote-sensing data (AVHRR) were coupled with abiotic factors to explore spatial and temporal vegetation patterns of the Flint Hills in Kansas and Oklahoma. This information should enable the detection of both natural (e.g., interannual variation in precipitation and temperature) and anthropogenic (e.g., climate change, over-grazing, land-use practices) stresses on this grassland ecosystem. Shifts in the spatial and temporal patterns of vegetation (as measured from NDVI by AVHRR) have been correlated with meteorological data (from 117 weather stations) to identify key abiotic variables that determined vegetation patterns across this region. In 4 years, the combination of annual precipitation and growing degree days was useful to detect spatial and temporal vegetation patterns of the Flint Hills. However, it is imperative that land-use patterns are known in order to assess adequately spatial and temporal patterns of vegetation in this area.},
	keywords = {LTER-KNZ},
	doi = {10.2307/3628435},
	author = {J. M. Briggs and Rieck, D.R. and Turner, C.L. and Henebry, G.M. and Goodin, D.G. and Nellis, M.D.}
}
@article {KNZ00588,
	title = {A technique for monitoring ecological disturbance in tallgrass prairie using seasonal NDVI trajectories and a discriminant function mixture model},
	journal = {Remote Sensing of the Environment},
	volume = {61},
	year = {1997},
	pages = {270 -278},
	abstract = {Natural and anthropogenic disturbance in tallgrass prairie communities can induce changes in plant species composition, including shifts in the relative abundance of C3 and C4 lifeforms. The asynchronous seasonality in greenness exhibited by C3 and C4 species enables monitoring of their relative abundance using temporal trajectories of sensor-derived vegetation indices, such as NDVI. We use close-range measurements made over 22 experimental plots at the Konza Prairie Research Natural Area (KPRNA) to evaluate seasonal trajectories in NDVI as a function of Full-size image (<1 K) ratio. The NDVI data were collected from each plot at approximately 10-day intervals throughout the 1995 growing season. Metrics for summarizing the temporal behavior of NDVI trajectories were derived from two transformations of the data: 1) a conventional approach plotting NDVI against day of year and 2) an alternative approach plotting normalized cumulative integrated NDVI against growing degree day. Discriminant function mixture models derived from each set of inetrics were used together with species composition data from the experimental plots to derive relative Full-size image (<1 K) abundances. Results show that both methods can classify the majority of cases into their correct Full-size image (<1 K) abundance category; however, the transformation using normalized integrated NDVI against growing degree day was a significantly better discriminator (p=0.0102). The techniques presented are effective for monitoring relative Full-size image (<1 K) abundance in tallgrass prairie; however, more investigation is needed to assess their performance at different spatial resolutions and in different geographic settings.},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.1016/S0034-4257(97)00043-6},
	author = {Goodin, D.G. and Henebry, G.M.}
}
@article {KNZ00534,
	title = {The effect of density dependence on community structure},
	journal = {Ecological Modelling},
	volume = {93},
	year = {1996},
	pages = {33 -42},
	abstract = {The effect of population density controls on the relationship between stability and species richness was explored by constructing Monte Carlo community models with density dependent population controls. Simulated communities with more initial species exhibit proportionally fewer extinctions. This form of stability is greatest at low interaction strengths and intermediate connectivities. Stability appeared to be related to the fact that species with more interactions were less likely to be driven to extinction by negative interactions. Species with mutualistic (+ / +) and commensal (0/ +) interactions survive at greater than expected proportions, while those with relatively more competitive (- / -) and amensal (0 / -) interactions tend toward extinction. Incorporation of density dependent population control thus leads to features that previous community models have not exhibited. It is suggested that communities with many of the populations controlled by abiotic factors in a density dependent fashion should exhibit increased stability with more species.},
	keywords = {LTER-KNZ, Community matrix, Competition, density dependence, mutualism},
	doi = {10.1016/0304-3800(95)00209-X},
	author = {W. K. Dodds and Henebry, G.M.}
}
@article {KNZ00533,
	title = {Nitrogen transport from tallgrass prairie watersheds},
	journal = {Journal of Environmental Quality},
	volume = {25},
	year = {1996},
	pages = {973 -981},
	abstract = {Discharge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha-1 yr-1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0\% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14{\textendash}0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO-3N and total N (r values = -0.43 and -0.20, respectively). Low N concentration is typical of these streams, with NH+4-N concentrations below 1.0 {\textmu}g L-1, NO-3-N ranging from below 1.4 to 392 {\textmu}g L-1, and total N from 3.0 to 714 {\textmu}g L-1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.2134/jeq1996.00472425002500050007x},
	author = {W. K. Dodds and John M. Blair and Henebry, G.M. and Koelliker, J.K. and Ramundo, R.A. and Tate, C.M.}
}
@proceedings {KNZ00543,
	title = {Seasonal NDVI trajectories in response to disturbance: toward a spectral-temporal mixing model for tallgrass prairie},
	year = {1996},
	pages = {215 -217},
	publisher = {IEEE},
	address = {Piscataway, NJ},
	abstract = {Natural and anthropogenic disturbance in tallgrass prairie communities can induce changes in plant species composition, including shifts in abundance of C3 vs. C4 lifeforms. The asynchronous seasonalities in greenness that C3 and C4 species exhibit should enable monitoring of their relative abundance using sensor derived vegetation indices, such as NDVI. The authors used close-range measurements made over 22 experimental. Plots at the Konza Prairie Research Natural Area (KPRNA) to evaluate seasonal trajectories in canopy greenness as a function of C3/C4 ratio. NDVI data were collected from each plot at approximately ten day intervals throughout the 1995 growing season. Temporal trajectories were used to develop discriminant functions to model relative C3/C4 abundances. The discriminant model yielded values of Kendall{\textquoteright}s τb and Cohen{\textquoteright}s κ statistic of 0.794 and 0.781, indicating strong agreement between classes and an overall classification significantly better than random assignment. Results suggest the possibility of applying spectral-temporal mixture models derived from close-range sensing to larger scale monitoring of tallgrass prairie},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.1109/IGARSS.1996.516295},
	author = {Goodin, D.G. and Henebry, G.M.}
}
@proceedings {KNZ00550,
	title = {Spatio-temporal dynamics of soil moisture in tallgrass prairie using ERS-1 SAR image time series: first year results},
	year = {1996},
	pages = {166 -168},
	publisher = {IEEE},
	address = {Piscataway, NJ},
	abstract = {Radar remote sensing of soil moisture has been demonstrated in croplands and rangelands. The authors are interested in synoptic estimates of soil moisture to aid long term ecological investigation of tallgrass prairie and have initiated a three year study to develop this technology. The authors{\textquoteright} study area, Konza Prairie Research Natural Area (KPRNA), exhibits a variety of factors to complicate soil moisture estimation via synthetic aperture radar (SAR) including significant terrain variation, heterogeneous soil types and depths, and watershed-level experimental treatments including prescribed burning, grazing by large ungulates, and water supplementation. Several indicators of the moisture status of soil-water-vegetation continuum were gathered during the 1995 growing season including soil moisture via neutron probe and TDR, xylem pressure,potential values, and aboveground biomass (wet and dry weights). Due to orbital track overlap, eleven ERS-1 SAR images of KPRNA were acquired from mid-April to early October. Spring through mid-summer were unusually cool and wet, thereby delaying phenological development and attenuating the water stress typical of the later growing season. Backscattering values show some consistent agreement with ground data. Watersheds burned in April showed markedly higher backscattering at the end of the growing season due to a lack of litter layer from previous seasons{\textquoteright} growth. Grazed units that were also burned showed the highest backscattering caused by no litter layer and more exposed soil},
	keywords = {LTER-KNZ, tallgrass prairie},
	url = {10.1109/IGARSS.1996.516279},
	author = {Henebry, G.M. and Alan K. Knapp}
}
@proceedings {KNZ00496,
	title = {Observing spatial structure in the Flint Hills using AVHRR biweekly composites of maximum NDVI},
	year = {1995},
	pages = {143 -151},
	keywords = {LTER-KNZ},
	author = {Henebry, G.M. and Su, H.},
	editor = {D.C. Hartnett}
}
@article {KNZ00484,
	title = {Simulation of responses of community structure to species interactions driven by phenotypic change},
	journal = {Ecological Modelling},
	volume = {79},
	year = {1995},
	pages = {85 -94},
	abstract = {We developed a community model which considers the effect of phenotype on species interaction in order to elucidate general relationships between phenotype, species interactions and community structure. The model consists of community matrices with density-dependent species interactions and a limit on the total population of each species. A general natural pattern forms the basis of the model: organisms which are most similar compete, those which are less similar may enter into a predator-prey relationship, and those which are most different may be mutualistic. In this model, contrary to some previously published studies, increasing the number of species increased stability of community matrices. The rate of change in phenotype was varied to assess the response of community characteristics. At the highest rate of random phenotypic change there were the most species; the minimum number of species was found at intermediate rates of change. The models were run in the absence of predation, competition, or mutualism. The absence of mutualism led to more extinction. The absence of competition caused communities to quickly reach a population ceiling. Results suggest that it is extremely important to understand the relative occurrence of mutualism and competition in natural communities. Furthermore, the rate of phenotypic change could be an important but subtle determinant of community structure.},
	keywords = {LTER-KNZ, Competition, interspecific, mutualism, networks, Species interactions},
	doi = {10.1016/0304-3800(94)00030-L},
	author = {W. K. Dodds and Henebry, G.M.}
}
@article {KNZ00495,
	title = {Spatial model error analysis using autocorrelation indices},
	journal = {Ecological Modelling},
	volume = {82},
	year = {1995},
	pages = {75 -91},
	abstract = {No standard techniques yet exist for assessing the predictive performance of models that simulate spatially-explicit processes. Spatial simulation models generate autocorrelation patterns that are a critical aspect of model prediction. These patterns can be quantified using spatial (Moran{\textquoteright}s I) and spatio-temporal (Griffith{\textquoteright}s STI) autocorrelation indices. A method of error analysis for spatial simulation models is demonstrated using autocorrelation indices to distinguish among the effects of parameter uncertainty on a stochastic spatial simulation of seed dispersal. The resulting autocorrelation patterns of state variables display a range of nonlinear, counterintuitive effects. In contrast to techniques proposed for spatial model error analysis (contagion, spatial predictability, adjacency, multiple resolution procedure, fractal dimension, interface), autocorrelation indices can be used with interval-scaled data and have well-defined sampling distributions that enable significance testing.},
	keywords = {LTER-KNZ, Autocorrelation, Error analysis, Spatial patterns, Uncertainty analysis},
	doi = {10.1016/0304-3800(94)00074-R},
	author = {Henebry, G.M.}
}
@article {KNZ00406,
	title = {Detecting change in grasslands using measures of spatial dependence with Landsat TM data},
	journal = {Remote Sensing of Environment},
	volume = {46},
	year = {1993},
	pages = {223 -234},
	abstract = {Spatial dependence is a fundamental structure of spatial data that can be readily measured. Change in landscapes can be monitored effectively using measures of spatial dependence. Scale of fluctuation analysis estimates the dimensional extent to which data are significantly autocorrelated by observing the behavior of sample variance under extended local averaging. Algorithms to estimate the one-dimensional scale of fluctuation (correlation length) and two-dimensional scale fluctuation (correlation area) in image data are described. The approach is demonstrated with an analysis of a 9-year TM image series of a tallgrass prairie preserve, Konza Prairie Research Natural Area, to assess the impact of bison on the spatial patterning of vegetation.},
	keywords = {LTER-KNZ},
	doi = {10.1016/0034-4257(93)90097-H},
	author = {Henebry, G.M.}
}
@article {KNZ00407,
	title = {Using landscape trajectories to assess the effects of radiometric rectification},
	journal = {International Journal of Remote Sensing},
	volume = {14},
	year = {1993},
	pages = {2417 -2423},
	abstract = {We demonstrate a simple procedure, landscape trajectories, for quantifying the effects of radiometric correction on image characteristics. Eleven Landsat Thematic Mapper (TM) images of tallgrass prairie spanning 1987 and 1988 were radiometrically rectified to a common date using a {\textquoteleft}pseudoinvariant features in real space{\textquoteright} method (Schott et ai 1988). The Normalized Difference Vegetation Index (NDVI) was calculated for each raw and corrected image. Four watersheds within the study area were subset and the images were decomposed into spectral intensity (SI), spatial eterogeneity (SH), and spatial dependence (SD) components. Time-ordered vectors in SI-SH-SD space described landscape trajectories. Vector lengths along trajectories were calculated and integrated. Differences between measures on raw and corrected images may be attributable to climatic forcings, time of season, time since fire, and watershed topography. The correction procedure changed SI most and SD least. While the rectification procedure was linear with respect to the entire scene, specific watersheds exhibited nonlinear responses to radiometric rectification.},
	keywords = {LTER-KNZ},
	doi = {10.1080/01431169308954046},
	author = {Henebry, G.M. and Su, H.}
}
