1. Influence of Chinese privet (Ligustrum sinense Lour.) on floodplain productivity and regeneration Eve Brantley, Jennifer Mitchell, and B. Graeme Lockaby Auburn University School of Forestry and Wildlife Sciences Center for Forest Sustainability

2. Ligustrum sinense Lour. Often forms dense thickets, particularly in bottomland forests and along fencerows Shade and flood tolerant Aggressive colonizer - spreads locally by root sprouts and widely by abundant bird- and other animal-dispersed seeds. Invasive Plants of the Eastern United States Present in all of the southeastern states and ranges north to Massachusetts

3. Objectives To determine how increasing densities of Chinese privet influence aboveground and belowground net primary productivity. Investigate influence of Chinese privet density on native plant regeneration

4. Study Sites 16 - 0.04 ha study sites selected in West Georgia Southern Piedmont Floodplains occupied by deciduous forests, closed canopy Georgia, USA Columbus GA LaGrange GA

5. Study Sites Sites represent a continuum of understory Chinese privet stem density (0 – 100%) Study sites

6. To determine how increasing densities of Chinese privet influence above- and belowground net primary productivity. Aboveground productivity: Monthly collection of litterfall (3 -.25 m 2 traps per site) Litterfall samples dried, weighed and analyzed for C, N, P Diameter at breast height (DBH) recorded annually for all stems greater than 10 cm DBH and used to estimate stem annual increment

7. To determine how increasing densities of Chinese privet influence above- and belowground net primary productivity. Belowground productivity: Two fine root samples collected every 6-8 weeks using soil core method (Vogt and Persson 1991, Anderson and Ingram 1993, Bledsoe et al. 1999) Samples collected to a depth of 11 cm and sorted size classes by live and dead fractions Samples dried, weighed and analyzed for C and N

8. Investigate influence of Chinese privet density on native plant regeneration Regeneration: 12 – 1 m 2 plots established at 3, 6 and 9M from site center on north, south, east, and west ordination After spring leaf out, vegetation in each regen plot less than 10 cm DBH will be identified to species and its height recorded

9. Statistics SAS version 9.1 Linear and non-linear regression All differences below p < 0.10 reported

10. Year 1 Results Increasing privet understory

11. Year 1 Results Chinese privet presence measured by proportion of understory - percent of understory that is Chinese privet (0 – 100%) Curvilinear and linear relationships between Net Primary Productivity and privet invasion Strong, negative relationship between Chinese privet invasion and native plant regneration

12. Net Primary Productivity and Chinese privet understory proportion Significant curvilinear relationship between –Total NPP & proportion of understory as privet (P < 0.008 R 2.5821)

13. Net Primary Productivity and Chinese privet understory proportion Significant curvilinear relationship between –Aboveground NPP & proportion of understory as privet (P < 0.05 R 2.4133)

14. Net Primary Productivity and Chinese privet understory proportion Significant nonlinear relationship between –Belowground NPP & proportion of understory as privet (P < 0.01 R2.5311)

15. Regeneration % Chinese Privet Understory (2004) compared with % Chinese Privet in Regeneration Layer (2005) y = 0.9688x + 5.9086 (p < 0.001 R2 = 0.933)

16. Regeneration % Chinese Privet Understory (2004) compared with % Native Species in Regeneration Layer (2005) y = -0.9641x + 94.115 (p < 0.001 R2 = 0.9472)

18. Year 1 Conclusions - NPP In southeastern Piedmont riparian areas Chinese privet appears to influence –Net Primary Productivity –Native species regeneration

19. As Chinese privet stem densities rise: ANPP is the greatest at medium levels of Chinese privet understory proportion (40-80%) ANPP is lower at the low (0-40%) and high (80-100%) levels of Chinese privet understory proportion

20. As Chinese privet stem densities rise: BNPP is the greatest at medium levels of Chinese privet understory proportion (40-80%) BNPP is lower at the low (0-40%) and high (80-100%) levels of Chinese privet understory proportion

21. Year 1 Conclusions – Regeneration Proportion of Chinese privet in the understory is strongly related to the regeneration layer –Increase in Chinese privet regeneration with increasing proportion of understory Chinese privet –Decrease in native species regneration with increasing proportion of understory Chinese privet ~ 50% understory privet, native regen drops below 40%

22. Acknowledgements Dr. B. Graeme Lockaby Dr. Kathryn Flynn Dr. William Conner Dr. James E. Hairston Jennifer Mitchell Don Vestal Robin Governo Lena Polyakova Rachel Jolley Jackie Crim Emile Elias Auburn University School of Forestry and Wildlife Sciences, Center for Forest Sustainability