Long-term response of oak-hickory regeneration to partial harvest and repeated fires: influence of light and moisture
Ecosphere. 8(1): e01642. 24 p.
By tracking oak-hickory (Quercus-Carya) regeneration for 13 yr across management-manipulated light and topographically driven moisture gradients after partial harvest and three prescribed fires, we document best-case conditions to promote advanced oak regeneration, and thereby provide a promising management tool to reverse the downward spiral in oak that plagues much of the Central Hardwoods within the eastern United States. This study was established in 2000 to assess regeneration following prescribed fire (spring of 2001, 2005, and 2010) in combination with partial harvest (late 2000) across two sites in southern Ohio. Each of the four 20+ ha treatment units (two partial harvest and burn, two controls) were modeled and mapped for long-term moisture regime using the Integrated Moisture Index (IMI) , and a 50-m grid of sampling points established throughout the units. Vegetation and light were sampled at each gridpoint before and after treatments, in 2000, 2001, 2004, 2006, 2009, and 2013. The partial harvest and burn treatments generally had more light which resulted in an increased number of oak stems. The fires promoted heterogeneity (pyrodiversity) in tree mortality and light availability, and consequently oakhickory regeneration, mostly following IMI patterns with the drier portions of the landscape having more fire, more light penetration, and greater regeneration compared to moist locations. Several other species also had marked variations in numbers and size throughout this period, depending on landscape variation in fire intensity and moisture regimes. These included Acer rubrum and Liriodendron tulipifera which expanded initially then collapsed after repeated fire, and Sassafras albidum which continued to flourish on dry sites. Based on this study, we recommend for topographically appropriate dry and intermediate sites, a partial harvest followed by two or three dormant-season fires (depending on fire intensity) allowing roughly 6-18% light to penetrate the forest floor. This will promote oak-hickory into the advanced oak regeneration status. Then, following a hiatus from burning for some years to further advance oak-hickory growth without topkill, some proportion of oaks and hickories can be expected to advance to the canopy following natural disturbance or harvest of current canopy. On mesic sites, though treatments demonstrated here do improve oak-hickory regeneration, the relative cost to benefit would be high.
Keywordscanopy openness; Central Hardwoods region; hickory (Carya); Integrated Moisture Index; maple (Acer); moisture regime; oak (Quercus); oak advanced regeneration; oak regeneration; Ohio; partial harvest; prescribed fire; topographic influences
Iverson, Louis R.; Hutchinson, Todd F.; Peters, Matthew P.; Yaussy, Daniel A. 2017. Long-term response of oak-hickory regeneration to partial harvest and repeated fires: influence of light and moisture. Ecosphere. 8(1): e01642. 24 p. http://dx.doi.org/10.1002/ecs2.1642