Species diversity and ecosystem productivity are generally correlated, and the nature of this correlation is thought to inform the rules of species coexistence and community structure. However, for logistical reasons, much of the work on this correlation has used herbaceous plants. Here I describe the results of a manipulative forest experiment containing 3 species (Quercus rubra, Prunus serotina, and Castanea dentata) planted in all 7 combinations of 1, 2, or 3 species and at three different densities (1m, 2m or 3m between trees). The experiment contains 63 plots and 2268 total trees. My goal is to study the productivity-diversity relationship at Martell using 2 objectives: 1) Determine the environmental drivers of productivity – diversity correlation. 2) Determine the competitive drivers of the productivity – diversity correlation.
Historical wood production was measured using dendrochronology cores and tree diameter-at breast height (DBH) measurements. Leaf production was measured using litter traps, with leaves separated by species, and weighed. Further, photosynthetic light curves were made at two heights within the canopy layers using an infra-red gas analyzer.
Results/Conclusions
As of summer 2018 the productivity-diversity correlation was not found within the leaf production or DBH. However, density did lead to a significant increase in biomass production as trees tend to grow more when further apart. However, there is a trend through time based on dendrochronology suggesting a positive productivity-diversity correlation may occur over time and that 13 years is simply too early for competition to have shaped the productivity of these plots. The gas exchange results indicated a high response curve from Oak trees within every diversity, however the Chestnut trees within the 3m location seem to have a higher photosynthetic rate. However, this could relate to the previous discovery that the 3m trees are growing more comparatively.