Plant community trends at Tallgrass Prairie National Preserve: 2002–2023

Leis, Sherry

doi:10.36967/2309785

The Heartland Inventory and Monitoring Network has monitored vegetation at Tallgrass Prairie National Preserve for more than 20 years. Monitoring assists the preserve in managing the nearly 10,000-acre (4,047 ha) site by providing status and trends of vegetation and disturbance metrics. The site protects critical remnant tallgrass prairie as well as the ranching legacy of the Flint Hills region. Monitoring was conducted in 30 permanent sites across the western preserve. We assessed current and future climate trends, fire and grazing rates, and vegetation metrics, including ground cover, guild, plant diversity, and species composition. We also assessed observer error using a double sampling technique. Historical climate data indicate a trend toward increasing moisture and days with heavy precipitation. Future climate scenarios include the possibility of a warm-wet future with a slight increase in excess moisture (runoff) in the spring and the possibility of a hot-dry future where water deficit spans most of the year. Disturbance intensity continued to be lower since 2006 when management shifted from more of a ranching-based paradigm towards an ecological paradigm with heterogeneity as a central theme (Leis and Morrison 2018). Stocking rates were similar or lighter than the prior monitoring period (2015–2018), and fire return intervals were longer since 2006. Of ground cover metrics, bare areas meet greater prairie chicken habitat thresholds preserve-wide but fall below expectations in two pastures. The native woody plant guild continues to increase in cover in Big and Windmill pastures, but other plant guilds are stable. There was a small increase in tree seedlings, however. Measures of species richness were within the range of variation of prior monitoring events, but Shannon Diversity had a declining trend. Combined with Sørensen index analysis we noted that species composition shifts were likely a key factor in the decline of Shannon Diversity. Pseudoturnover was less than the previous monitoring event—likely the result of having an expert botanist and improved double sampling techniques and communication. Indications of a changing flora coincide with reduced disturbance intensity and a changing climate. An increase in disturbance intensity and/or timing shifts may be needed to avoid detrimental woody plant expansion. Future management actions that take climate scenarios into consideration may also be beneficial. For example, planning fires around changing plant phenology and grazing plans that reduce animal stress and provide adequate water in the event of drought would be beneficial in the short and long term.

Plant community trends at Tallgrass Prairie National Preserve: 2002–2023

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