Woodland succession after multiple intense disturbances: Manley Woods, 1998–2017

Leis, Sherry; Short, Marry

Natural community management at Wilson’s Creek National Battlefield (NB) is shaped by our understand- ing of the woodlands and prairies at the time of the Civil War battle in 1861. This report is focused on the Manley Woods unit of the Battlefield, which is an oak-hickory woodland in the Springfield Plain subsection of the Ozarks. Canopy closure for Missouri oak woodlands can be highly variable and can range from 30-100% across the spectrum of savanna, open woodland, and closed woodland types. In 1861, the woodland was likely a savanna community. Over time, woodlands at Wilson’s Creek NB, as well as across the Ozarks, began to increase in tree density, transitioning to a closed canopy woodland because of changes in land use history, including fire exclusion. Management plans eventually included restoring the area to a savannah/open woodland structure using fire. Prescribed fire was eventually reintroduced to Wilson’s Creek NB in 1988, and managers have been working towards open woodland targets using fire as a primary mechanism to reduce the canopy over time. The Manley Woods unit of Wilson’s Creek NB has been subject to intense natural and anthropogenic distur-bance events such as a tornado in 2003, timber removal in 2005, prescribed fires in 2006 and 2009, an ice storm in 2007, and periodic drought. The Heartland Inventory and Monitoring Network (hereafter, Heartland Network) installed four permanent monitoring sites within the Manley Woods area of the park in 1997. Initially, we assessed ground flora and regeneration within the sites (1998–1999). We added fuel sampling after the 2003 tornado. Although overstory sampling occurred prior to the tornado, the protocol was not yet stabilized and those data were not included in these analyses. Manley Woods has undergone substantial change in the monitoring period (1997–2017). Manley Woods contin-ues to have characteristic open oak woodland structure, but it is at a tipping point towards a forest community type rather than the more open target structure (i.e., savanna). The 2003 tornado introduced considerable heterogeneity to Manley Woods that continues to persist. Managers were concerned about oak and hickory regeneration in Manley Woods so a fire-free interval of about seven years was recommended to allow young oak and hickory trees to reach a fire tolerant stage. The eight-year long break in fire application successfully supported recruitment of saplings and class 1 trees (midstory trees; 5–14.9 cm diameter at breast height [DBH]), but fuels and canopy closure are elevated. The expansion of class 1 trees may have exceeded expectations and may be contributing to current canopy closure. Tree species composition indicates an increase in some meso-phytic species. The ground flora layer of the woods also responded to the changes in structure and disturbance. Ground flora species richness increased in the last monitoring period. Remarkably, few exotic species have been observed in the woodland. Continued dominance of the woodland by oak species will require that prescribed fire be restarted soon and periodic fire implemented to thin the midstory layer. To achieve a savanna-like (open wood-land) structure, shorter fire return intervals may be needed in the short-term.

Woodland succession after multiple intense disturbances: Manley Woods, 1998–2017

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