Stacy L. Clark

DYNAMICS OF OAK (QUERCUS MARILANDICA AND Q. STELLATA) REPRODUCTION IN AN OLD-GROWTH CROSS TIMBERS FOREST

Abstract We present a case study from three topographically distinct stands in an old-growth cross timbers forest in north central Oklahoma. We determined the primary mode of reproduction, i.e., sprouting versus seedling, and population dynamics of small Quercus marilandica and Q. stellata reproduction (≤ 1 m height) in relation to previous disturbance events and changes in site conditions. Approximately 99 percent of the reproduction were of sprout origin and most were stump sprouts (root crown diameter > 5 cm). Surprisingly, root sprouts were an important component of reproduction across stands, comprising 24 and 30 percent of stems for Q. marilandica and Q. stellata, respectively. Mode of reproduction varied by stand, with seedling sprouts (root crown diameter ≤ 5 cm) occurring more frequently on the most xeric site. Stem growth rates increased from xeric to mesic stands and were highest for stump sprouts. Stem longevity was similar across stands and mode of reproduction and was probably limited by low available light. Despite the relatively short life span of aboveground stems (x̄ ∼6 years), tap-roots of seedling sprouts were capable of prolonged persistence (x̄ ∼20 years) through recurrent dieback and sprouting. Stem age structure indicated disturbance encouraged sprouting, as evidenced by increasing populations following fire and declining densities in the absence of perturbation. Seedling establishment for both species appeared to be episodic, as determined by age of tap-roots. Establishment by acorns probably provides a minimal input to oak populations on a yearly basis, but is an important component in the auto-accumulation of oak reproduction over time.

Fire in Eastern Hardwood Forests Through 14,000 Years

Fire helped shape the structure and species composition of hardwood forests of the eastern United States over the past 14,000 years. Periodic fires were common in much of this area prior to European settlement, and fire-resilient species proliferated. Early European settlers commonly adopted Native American techniques of applying fire to the landscape. As the demand for wood products increased, large cutover areas were burned, sometimes leading to catastrophic fires and subsequent early successional habitats. By the early 1900s, these catastrophic fires resulted in political pressure leading to policies that severely restricted the use of fire. Fire suppression continued through the twentieth century due to an emphasis on commodity production and under-appreciation of the ecological role of fire. Without fire, fire-sensitive species were able to successfully outcompete fire-adapted species such as oak and pine while early successional habitats matured into older and more homogeneous forests. In the late twentieth century, land managers began reintroducing fire for ecosystem restoration, wildlife habitat improvement, hazardous fuel reduction, and forest regeneration. Responsible expanded use of xadprescribed fire and other management tools in the region could help mitigate past actions by increasing the amount and distribution of early successional habitats, plant and animal diversity, and landscape heterogeneity.

CAN OAKS BE AGED FROM BUD SCARS

Abstract We assessed the ability to age post oak (Quercus stellata) and blackjack oak (Q. marilandica) reproduction less than 100 cm in height using counts of terminal bud scars. We harvested reproduction from an old-growth Cross Timbers forest in north-central Oklahoma and compared age estimates from bud scar counts with actual age determined from annual ring counts. Approximately 71% of reproduction was accurately aged by counting bud scars. The majority of errors in age estimation were underestimates. We could accurately estimate age to within 2 years of the actual age 96% of the time. Error rates were similar between species and across height classes, but increased with age of reproduction. Damage to the stem from deer browsing or disease also increased age estimation error. This method might be especially applicable to oak forests that have low levels of herbivory and where nondestructive sampling techniques are required.