Woodland Succession after Multiple Intense Disturbances

Monitoring site 4 in Manley Woods at Wilson’s Creek National Battlefield, 2006. The image was taken three years after a tornado and less than one year after a fuel reduction burn.

NPS-Photo

Inset of Wilson’s Creek National Battlefield on the right and magnification of Manley Woods with sample sites labeled on the left (2016 image).

NPS

Natural community management at Wilson’s Creek National Battlefield (NB) is shaped by our understanding 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 [right]. The Manley Woods unit of Wilson’s Creek NB has been subject to intense natural and anthropogenic disturbance 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.

Manley Woods has undergone substantial change in the monitoring period (1997–2017). Manley Woods continues 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).

Year	Mean basal area (m2/ha)	±CI	Mean Density (stems/ha)	± CI	Stocking (%)	± CI
2003	16.6	15.7	510	39.3	42.3	39.5
2006	12.2	18.3	337.5	38.1	31.2	46.6
2017	14.2	11.3	870	23.1	35.4	29.8

Mean basal area (m²/ha) and tree density (stems/ha) were used to determine stocking density in the Manley Woods unit of Wilson’s Creek National Battlefield from 2003 to 2017 (N =4). 95% confidence intervals (CI).

Canopy closure in the Manley Woods unit of Wilson’s Creek National Battlefield 2003–2017 (N =4).

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 (5–14.9 cm diameter at breast height [DBH], aka midstory trees), 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 mesophytic 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.

Mean site native species richness for Manley Woods unit at Wilson’s Creek National Battlefield from 1998 to 2017. Dashed lines indicate a 95% confidence interval calculated from pre-tornado data.

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 woodland) structure, shorter fire return intervals may be needed in the short-term.

View the Full Report. (pdf)

View related article from 2008.

For more information visit the Heartland Inventory & Monitoring Network homepage.


Data in this report were collected and analyzed using methods based on established, peer-reviewed protocols and were analyzed and interpreted within the guidelines of the protocols.