Effects of understory management on trade-offs and synergies between biomass carbon stock, plant diversity and timber production in eucalyptus plantations

Understory vegetation management is prevalent in successive short rotation eucalyptus plantations to control interspecies competition and improve tree growth and timber yields. Managing for multiple ecosystem services is critical for sustainable forests. Yet trade-offs and synergies between plant diversity, biomass carbon stock, and timber yields under different management approaches is poorly understood. Using eucalyptus plantations under different understory vegetation management approaches, in subtropical China, we examined the effects of understory vegetation management on tree growth, biomass carbon stocks, timber production, the composition and diversity of understory plant communities. We then assessed trade-offs and synergies among biomass carbon stocks, plant diversity attributes and timber production. Manual band tending (manual removal of the above-ground portion of understory vegetation in a 1 m band around the eucalyptus trees) did not affect the diversity of understory plant communities and favored biomass carbon stock and timber production. Thus, this treatment resulted in positive synergies between biomass carbon stock, plant diversity and timber production. Repeated broadcast herbicide application led to declines in understory plant diversity and increased exotic plant invasion, but also improved biomass carbon stock and stand volume. Trade-offs favoring carbon stock and timber production existed in broadcast herbicide application plots. Intensive disturbance of the understory and 0-5 cm topsoil removal led to declines in biomass carbon stock, plant diversity and timber production, and a negative synergy existed among these services. Our results confirm that manual band tending of understory vegetation in eucalyptus plantations, which results in positive synergies among plant diversity, biomass carbon stock, and timber production, should be a favorable management strategy for multiple ecosystem services. Although broadcast herbicide application can effectively improve carbon stock and timber production, attention should be paid to controlling invasive species after application.