Leaf palatability and decomposability increase during a 200-year-old post-cultural woody succession in New Zealand

Question: How do aggregate trait values and functional diversity of leaf traits linked to palatability and decomposability change during a woody post-cultural succession spanning 200 years? Location: Coastal Marlborough, South Island, New Zealand. Methods: The biomass of all woody species was determined in 32 20-m x 20-m plots ranging from 10 to 200 years in time since last disturbance. Species abundances were combined with data on leaf nutrient, secondary metabolite and structural carbohydrate content to calculate biomass-weighted trait means (i.e. aggregate trait values) and functional diversity index values for each plot. Aggregate trait values and functional diversity were regressed on successional age and total live above-ground carbon content to examine functional shifts with succession and one consequence of succession - increasing above-ground carbon. Results: Almost all significant regressions between aggregate trait values and both successional age and above-ground carbon indicated a shift toward increased leaf palatability and decomposability during succession. The relationships were all non-linear, with aggregate trait value shifts occurring relatively early in the successional sequence. There was weak evidence for an increase in functional richness with succession, but this was a secondary effect relative to the shifts in aggregate trait values. Conclusions: These results are in direct contrast with studies of the early stages of herbaceous post-cultural successions from grasslands to shrublands, which have found a shift towards communities of decreasing palatability and decomposability, suggesting that functional shifts in woody succession may be fundamentally different.