Utilizing remote sensing to quantify grassland stability in response to drought

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Eric T. Allen, Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, OK, Lara Souza, Oklahoma Biological Survey and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK and Xiangming Xiao, Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK

Background/Question/Methods
Drought is known to have negative impacts on vegetation productivity and function; therefore, understanding grassland stability and resilience to drought is important in the context of current and future climate variability. Understanding the effects of drought and ecological responses, such as stability and resilience of net primary productivity, is imperative for future assessment and mitigation of the negative effects of drought on ecosystems. Quantifying stability and resilience of vegetation over the course of a drought may be useful for understanding how ecosystems are responding to drought. While most stability assessments have been conducted at small spatial scales (e.g., < 10 m2 plot level), we plan to quantify the stability and resilience of grasslands in Cimarron County, Oklahoma (an area prone to frequent and intense drought) using remote sensing datasets and techniques. The timeframe of this study is a 17-year period from 2004-2020 in which three separate drought events occur, including Oklahoma’s most intense drought in the last 50 years. Specifically, we will quantify stability by calculating overall fluctuation of NPP over the course of the total timeframe. Resilience will be determined by calculating decreases of NPP following the onset of drought, relative to control values.
Results/Conclusions
Standardized Precipitation Index results indicate three consecutive drought periods, each with increasing intensity and longevity. Utilizing this quantified drought data, we will determine stability, resistance, and recovery relative to drought severity. We have also found extensive shrubland encroachment into grasslands across our study areas. From 2010-2019 alone, shrubland acreage increased over 400%, while grassland acreage decreased by almost 40%.This increase in shrubland and decrease in grasslands may influence stability through altering the resistance and recovery of the area’s ecosystems to drought. Understanding the stability and resilience of vegetation within Cimarron County may help pinpoint areas at most risk of productivity decline and degradation following extended drought.