Research addressing the relationship between biodiversity and ecosystem function abounds (Balvanera et al. 2006; Cardinale et al. 2012) though most researchers have focused on the effects of either intraspecific or interspecific diversity on ecological function. Research at Cedar Creek and elsewhere has documented associations between species diversity (?interspecific diversity?), species interactions and many ecological functions, including primary productivity, nutrient cycling, soil and water quality, ecosystem stability, and resistance to invasion. (Tilman et al. 1996; Symstad et al. 2003; Hooper et al. 2005; Balvanera et al. 2006; Quijas et al. 2010) In parallel, research in systems such as goldenrod (Crutsinger et al. 2006, 2008a,b, 2009; Souza et al. 2011) and poplar (Schweitzer et al. 2004, 2008; Bailey et al. 2005; Madritch et al. 2009; Fischer et al. 2010; Courty et al. 2011; Lowejewski et al. 2012; Robinson et al. 2012), among others, has demonstrated the relationship between genotypic diversity (?intraspecific diversity?) and a similar group of functions that include primary productivity; nutrient cycling; resistance to invasion; ecosystem stability; microbial, epiphyte, and arthropod community diversity; litter decomposition; and fungal endophyte and mycorrhizal associations. Taken together, these two discourses suggest that interspecific and intraspecific diversity jointly drive species interactions and structure ecosystem processes including primary productivity, nutrient dynamics, resistance to and resilience following disturbance. Yet the relative roles of intraspecific versus interspecific diversity in structuring these processes remain uncharacterized.
Several groups of investigators have explored the consequences for ecological function of varying intraspecific diversity of a focal species and interspecific diversity of its surrounding community (Booth and Grime 2003; Cook-Patton, et al. 2011; Hargrave et al. 2011; Whitlock et al. 2011; Chang et al. 2012; Crawford et al. 2012; Genung et al. 2012). Yet few studies have experimentally varied both intraspecific and interspecific diversity across multiple species in a direct and fully factorial manner (see Fridley and Grime 2010). We still do not understand the relative role of each in driving the production of ecosystem services. The paucity of research addressing such questions constitutes a gap in our knowledge of the relationship between biodiversity and ecosystem services. The central goal of this study is to clarify how variation in critical ecological functions is partitioned between intraspecific and interspecific plant diversity. The partitioning of the impact of diversity on ecological function into interspecific and intraspecific effects speaks to basic principles of wide interest to the ecological community. (Hooper et al. 2005; Cianciaruso et al. 2009; Loreau et al. 2010; Hausch et al. 2011; Thorpe et al. 2011)
The specific aims of this project are to i) create an ecologically realistic, artificial plant community in which to investigate the relationship between biodiversity and ecological function over the next 5-15 years, ii) assess the unique and interacting effects of intraspecific tree diversity and interspecific tree diversity as drivers of ecological function in the community, and iii) provide a platform for collaboration with colleagues at the University of Minnesota and elsewhere who could take advantage of the study system to ask related questions. We hypothesize that: i) focal plant and whole ecosystem metrics of ecological function will be higher in the presence of higher intraspecific and interspecific tree diversity, ii) we will observe an additional synergistic increase in function as both types of diversity are experimentally increased, and iii) ecological functions will respond to increasing diversity in unique ways. The primary motivation for this project is to orthogonally assess the roles of intraspecific and interspecific diversity in driving ecological function.