1. Single-cohort Mixed Species Deciduous Stands Exhibiting Multi-cohort Attributes in the Southeastern United States Wayne K. Clatterbuck Silviculture & Forest Management Forestry, Wildlife & Fisheries University of Tennessee, Knoxville wclatterbuck@utk.edu

2. Overview 1. Examine stand structure in four stands within east TN with seemingly multi-cohort attributes 2. Hypothesize why stands are actually single-cohort 3. Are multi-cohort stands feasible in these forests?

3. Study Area Selection Second Growth Stands from a Stand Initiation Disturbance Age > 100 years, no major disturbances during period Multiple Canopy Layers At least 20 ha in size Government-owned – state or federal

4. Four Study Areas Cumberland Mountains (East Tennessee) Cumberland Plateau (East Tennessee) Smoky Mts National Park (East TN) Pisgah National Forest (Western North Carolina)

5. Site Characteristics Productive Cove Hardwood Forest Types, SI = 28 m at 50 years, mesic sites 65 inches or 160 cm annually Composed of more than 25 species Located in concave areas that escaped weather events that are frequent

6. Species Shade Intolerants --- Yellow- poplar, black cherry, black walnut, sweetgum, sycamore, cottonwood Intermediates --- white oaks, red oaks, hickories, ash Shade Tolerants --- red maple, hornbeam, sourwood, dogwood, buckeye, elm

7. Species Though sugar maple and American beech are present, they are on outskirts of range and are not prominent Assumption: too warm and humid for these species No commercially available shade-tolerant specie present, making multi-cohort management problematic

8. Diameter Distribution 1 hectare = 2.4 acres1 inch = 2.5 centimeters

9. Diameter Distribution 1 hectare = 2.4 acres1 inch = 2.5 centimeters All 4 Study Areas had similar diameter distributions

10. Structure Negative exponitial (reverse J-shaped) diameter curves Multi-species with different shade tolerances All within the same age range (+ or - 10 years), EVEN-Aged or single-cohort

12. Diameter Distribution 1 hectare = 2.4 acres1 inch = 2.5 centimeters Composed of shade-tolerant, non-commercial species --- (Cornus, Oxydendron, Nyssa, Acer rubrum, Sassafras, Ulmus)

13. Why Single-Cohort and Differing Diameters? 1. Mixed Species 2. Stand-Initiating Disturbances

14. Mixed Species Different species grow at different rates (tolerances) Different regeneration mechanisms Different rates to maturity by species Different responses to disturbance Different ???

15. Disturbance Disturbance is rampant on the landscape Varies by frequency and intensity Natural and anthropogenic

16. 1.Frequent stand initiating disturbance –Windstorms ---- tornados, hurricanes, storms –Fire --- formerly more prevalent –Insects/Disease outbreaks Difficulties with Multi-Cohorts

17. Average Number of days with thunderstorm events each year Source: Kim Coder, University of Georgia

18. Source: National Geographic

19. Source: National Weather Service

20. Insects & Disease Invasives Emerald Ash Borer Thousand Cankers Disease of Walnut Hemlock Woolly Adelgid Gypsy Moth Southern Pine Beetle Oak Decline

21. 2. Ecology of the various species present – No commercially available shade-tolerant species – Aggressive Liriodendron (yellow-poplar) --- a pioneer and late successional species –Do not know species composing late-successional complex because of frequent disturbance –Thus, must pay attention to regeneration to be sustainable Difficulties with Multi-Cohorts

25. 3. Short ownership intervals –85% of forest land (4.6 million ha) in Tennessee are in private woodland ownership –According to last Woodland Owners Survey, average forest tenure is 12 to 15 years Difficult to maintain multi-cohort stands with constant turnover Difficulties with Multi-Cohorts

26. 4.Surrogate of using diameter rather than age in representing multi-cohort stands –Large diameter trees are not necessarily old –Small diameter trees are not necessarily young –Wide variation in development of multi- species stands Difficulties with Multi-Cohorts

27. Bottomline Question: Do we desire multi- cohort stands in mixed mesophytic forests? We already have the structure w/o much effort, although single- cohort

28. Bottomline Stands are: Complex / Variable / Heterogenous Functionally Resilient Flexible/Adaptable Challenging because of frequency of change

29. Bottomline The challenge for multi-cohort stands is: Regenerating acceptable species (primarily intolerants and intermediates) in the shade of the overstory when desirable shade tolerants are not part of the system

30. Bottomline Even with the rapidity of major disturbances, we can create even more variability, if desired, through incomplete disturbances, more than likely on an area basis (groups and small patches) Challenge is still regeneration of favored species

31. Bottomline Sustainability in these frequently disturbed systems is an open question because of the difficulties in regeneration But still many opportunities !!!

32. Next Creating and maintaining stable, mixed hardwood-pine stands (oak-pine) when each component is favored at different successional stages and with varying longevities Stay Tuned

35. Questions?