Opposing intra vs. interspecific diversity effects on herbivory and growth in subtropical experimental tree assemblages
Created at: 2016-11-03
Envisaged journal: Journal of Plant Ecology
Envisaged date: 2016-11-03
Positive plant diversity-ecosystem function relations are ultimately driven by variation in functional traits among individuals that form a community. To date, research has largely focused on the role of species diversity for ecosystem functioning. However, substantial intraspecific trait variation is common and a significant part of this variation caused by genetic differences among individuals. Here, we studied the relative importance of species diversity and seed family diversity within species for growth and herbivory in experimental subtropical tree assemblages.
In 2010, we set up a field experiment in subtropical China, using four species from the local species pool. Trees were raised from seeds, with seeds from the same mother tree forming a seed family. We established 23 plots containing one or four species (species diversity treatment) and one or four seed families per species (seed family diversity treatment). Tree growth (stem diameter, plant height and crown expansion) and herbivory (percentage leaf loss due to leaf chewers) were monitored annually from 2011 to 2013.
Tree species richness promoted growth but had no effect on herbivory. In contrast, seed family diversity reduced growth and increased herbivory, but only so in species mixtures. Most of the observed effects were time-dependent, with the largest effect found in 2013. Our results suggest that biodiversity can affect plant performance directly via tree species-species interactions, or, context-dependent, via potential effects on inter-trophic interactions. Two important conclusions should be drawn from our findings. Firstly, in future studies regarding BEF relationships, intraspecific genetic diversity should be given similar weight as species diversity as it has often been neglected and its effects are not well understood. Secondly, we demonstrate opposite effects of biodiversity among and within species, stressing the importance to consider the effects of multiple levels of biodiversity simultaneously.
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