Those of you who actually know me probably know that I’ve just taken a new job as a post-doc at Bournemouth University looking focussing on thresholds and non-linear change in forests. For those of you that didn’t know that I thought I’d briefly describe what we are trying to do on the project.
Regime shifts, when the state of an ecosystem changes rapidly from one relatively stable state to another, have been seen in many different types of ecosystem. The example normally used to illustrate this that gradual increases in nutrient input to lakes can lead to a rapid, unpredictable shift from clear to turbid, eutrophic states. Similar rapid changes have been suggested in tropical and boreal forests which have the potential to shift from closed forest to savannah or treeless states in relatively dry areas following fires. These fires can cause catastrophic death of huge number of trees and with the dry climate limiting regeneration due to unfavourable conditions for seed germination. There have also been suggestions that interactions between logging, fire, fragmentation and other disturbances may result in changes to ecosystems that are difficult to reverse.
However, it is currently difficult to gauge when, and where such dramatic shifts are likely to occur. This is a major concern because these regime shifts would inevitably have dramatic effects on the species found in ecosystems as well as the ecosystem services supplied by them. If human disturbance has the potential to cause regime shifts in forests, as appears likely, we are in trouble. The majority of forests in the world are now degraded and millions of people live in and around them. This is why I think that a deeper understanding of how humans can cause dramatic changes in forests as a result of degradation deserves more attention.
To look at this we are starting with a case study based in the New Forest in the UK. This area is, despite it’s name, largely open heathland and bog. However, within the New Forest there are also areas of woodland many of which have been unmanaged for the past 200 years. In some of these woodlands we have noticed that large trees seem to be dying but no regeneration is taking place, resulting in once forested areas turning from this…
….relatively open grassland or bracken dominated areas. For the first bit of work in the project we have been exploring the temporal changes in woodland structure and biodiversity and will be exploring what might be causing this die-off and stopping regeneration. We have a hunch as to what’s going on, and it looks a bit like this:
…but that is really a topic for another blog post.
More broadly we want to investigate non-linear changes in forests as a result of natural and human disturbances, exploring when and where tipping points are most likely to occur and forest recovery from dramatic change. For a number of these ideas I will be looking for collaborators who have datasets that might be useful for addressing these questions. If you think you might be have a dataset that would be useful for testing some of these ideas or are just interested in what we’re up to drop me an email. I can’t guarantee that I’ll get back to you very quickly at the moment though as I’m taking unpaid leave for the next 12 weeks. I should be back blogging by New Year.