Productivity-diversity relationships in hardwood plantations

Productivity of forest ecosystems contributes $17 billion annually to the economy in Indiana through forest products, and $200 billion to the national economy. The diversity of trees in these forests is considered a conservation value by society, and alsoils critical to fostering wildlife resources. Increasingly, following harvest of natural timber stands, forest managers and families in Indiana are turning to timber plantations to supplement their economic well-being. There is an opportunity to develop management advice from basic and applied ecological research that can aide in the design of these increasingly important forest plantations. Indeed, ecologists have shown that productivity and species diversity are correlated, but currently, the mechanistic causes of the productivity – diversity correlation remain unresolved. This means that we know that mixed species plantations will be more economically productive than single species plantations, but it is currently not possible to predict how many (and which) species should be planted to maximize timber production and economic value. Indeed, the productivity – diversity relationship shows that the same number of species can produce very different production outcomes, suggesting the importance of selecting compatible species and applying effective management. Rigorous field experiments are needed to examine mechanisms supporting this relationship. A 12-year-old experiment of three fine hardwood species planted as monocultures and species mixtures at varying densities is now a closed canopy forest. We have ongoing studies of species diversity and ecosystem productivity in these stands, and trends for the productivity – diversity relationship have emerged. Over the next three growing seasons, we propose to continue to evaluate functional, chemical, and structural traits, and add measurements of belowground productivity. This is a unique opportunity where basic and applied science, economic values and conservation values are nearly perfectly aligned. We have three objectives: (1) to characterize the productivity – diversity relationship in an existing long-term plantation experiment; (2) seek a mechanistic understanding of the causes of this relationship so that it can be predicted and generate management advice, and; (3) disseminate findings to landowners in the Midwest with extension field days and programs to help guide plantation management.

(Funding: HTIRC, AgSeed, American Chestnut Foundation)