Assembly history and ecosystem function
Ecologists have become increasingly aware that ‘assembly history’, or the sequence and timing in which species join an ecological community, may profoundly influence community structure (e.g. species diversity and composition).
There is also increasing evidence that community structure can control ecosystem functioning (e.g.decomposition, nutrient cycling, and plant productivity). However, what remains unclear is how historically derived differences in community structure may in turn affect ecosystem functioning. The current lack of historical perspectives on ecosystem functioning may be responsible for the apparent idiosyncrasies often observed in ecosystem functioning.
We are using fungal communities in fallen wood as a model system to investigate how the history of fungal community assembly regulates ecosystem functioning (e.g.wood decomposition and nutrient cycling) in New Zealand beech forests. Laboratory experiments are being used to determine whether the impacts of assembly history on ecosystem functioning depend upon soil fertility and fungivory. We will also perform a field experiment to determine the relative importance of assembly history against the natural background of environmental variability. We believe this project will provide new ecological insights by showing that historical information, though difficult to obtain in nature, can be essential for explaining seemingly idiosyncratic variation in ecosystem functioning.
Assembly history is also important in understanding succession and weed impacts. We are studying this through ongoing work on chronosquences and by investigating the effect of removal of particular plant guilds (plant groups sharing functional traits) on riverbed succession.
Although driven by ecological theory, our work on assembly history is directly relevant to applications. For example, community assembly research provides an ecological basis for understanding why some introduced species affect ecosystem function more greatly than others do, and how we can more effectively manage them. Similarly, our research seeks to build scientific foundations for ecological restoration - the effort to reassemble natural, self-functioning communities. Research on assembly history also links to our work on the reversibility of weed and herbivore impacts, and how pests influence ecosystem trajectories.
This work is funded by the Marsden Fund of the Royal Society of New Zealand.