# Grassland Wildfires in the Southern Great Plains: Monitoring Ecological Impacts and Recovery
## 3 Results  
Effect of Wildfire on Vegetation Greenness--Pair-Wise Comparison of Vegetation Indices between Fire-Affected and No-Fire Areas  
During the pre-fire period (winter and spring) the fire-year and 3 year prior NDVI values were similar (Figure 2). For 1 month post-fire, the NDVI values for burned plots dropped due to loss of biomass and the burnt surface which had low reflectance. During the green-up period in late spring to early summer, both burned and unburned plots had rapid increases in NDVI. By June, the burned and unburned plots had similar values of NDVI and were similar to the 3 years prior values. While the NDVI during the peak summer growing season in the first year post-fire was similar to 3 years prior values for the 2016 Anderson Creek fire, the post-burn mid-summer NDVI was lower than 3 years prior values for the Starbuck and Perryton fires, which occurred in 2017. The Perryton site and, to a lesser degree, the Starbuck site, showed a rebound in NDVI in the fall in the burned plots compared to the unburned plots. The US Drought Monitor ([[https://droughtmonitor.unl.edu](https://droughtmonitor.unl.edu)]([https://droughtmonitor.unl.edu](https://droughtmonitor.unl.edu)), Accessed on 13 December 2019) indicates that, for the Southwest Kansas, Texas High Plains, and Oklahoma Panhandle and North Central climate regions, the summer of 2016 and 2017 were less dry than spring or fall of those years, and that 2017 had higher drought levels than 2016. While there may have been differences in post-fire species composition responses or grazing pressure for the different fires that could be reflected in the NDVI values, no data are available to evaluate those impacts. The EVI is related to the chlorophyll content of the vegetation so we anticipated a reduction in EVI following wildfire. As with the NDVI, the winter and spring pre-fire EVI values (Figure 3) during the study year were low and similar to values observed during the 3 years prior period. Following the burn event, the EVI dropped in the burned plots, but the response was of lower magnitude and shorter duration for the Starbuck and Perryton fires than for the Anderson Creek fire. For all three fires, the EVI increased rapidly on burned and unburned plots during the green-up period. In contrast to the NDVI, the EVI on the burned plots reached or exceeded the unburned EVI values by mid-summer. However, the EVI values dropped in late summer, and were lower than 3 years prior values for the Starbuck and Perryton fires. At the Perryton site, which included a greater number of shrubs than the other two sites (Table A1), the EVI index for the burned plots remained significantly above the unburned plots through the fall and exceeded 3 years prior EVI values in October and November. Figure 2: Three year average Normalized Difference Vegetative Index (NDVI) values for the unburned plots (blue shaded) and burned plots (red shaded) of the Anderson Creek (top), Starbuck (middle), and Perryton (bottom) wildfires. Purple shaded area is overlap of burned and unburned plots in this and subsequent figures. Fire year NDVI averages for the unburned (blue) and burned (red) plots are shown as solid lines with error bars of one standard deviation. Time of fire is marked by grey shaded columns. The LSWI, which is related to water in vegetation and soils, showed a strong response to the fire events (Figure 4), with a pronounced decrease in LSWI on the burned plots compared to the unburned. The unburned plots have a higher leaf area and maintained a higher LSWI through early spring, though the burned plots showed a rapid increase during late spring to early summer as the leaf area recovered. By June, when the canopies were fully closed, the indices of the burned and unburned plots were similar. The summer EVI values were similar to the 3 years prior values for the Anderson Creek fire but lower than 3 years prior values for the Starbuck and Perryton fires. For the Perryton fire, the LSWI was higher in the burned than unburned plots during fall.