23 November 2011

Dirty needs non dirt heap

As I mow my relatively small lawn I am always faced with what I should do with the lawn clippings. I could put them in a green waste bin or put them back into my garden soils. I usually go for the latter - it's easier and I feel like it's a better option for my garden. Nutrients go back into the soil, carbon is contained in my property, I don't get a sore back from carrying the catcher to the bin. The same decision making probably happens all over the world in people's yards. Given the sheer area of urban soils around the world this is probably an instance of where lots of small decisions add up to a major impact on the world around us. Just how useful is putting greenwaste back into the soil?
Nick Dickinson moved to New Zealand last year to take up a position as the Head of the Department of Ecology at Lincoln University. In between earthquake aftershocks he has found time to publish on this issue of urban soils with Luke Beesley. In a study published in Soil Biology and Biochemistry, Nick looks at what happens to dissolved organic carbon and heavy metals under different soil treatments.


Nick set up experimental containers of soil and added greenwaste to some, biochar (a coal-like product) and noncomposted woody material in others. He also looked at the affect of adding earthworms as they churn the soil. The experiments were left for two months before water was collected from each and analysed for dissolved organic carbon and heavy metals. Addition of the various materials all contributed to increased mobility of dissolved organic carbon and heavy metals (rather than staying 'locked' into the soil they were moving around in water). Greenwaste seemed to increase this mobility compared to the biochar and woody materials. Earthworms also contributed to this mobility.
What does this mean for urban soils? While these additions increase the health of the soil, often urban soils are high in heavy metals. Ideally we do not want these metals to move out of the soils where they could contaminate ground water. Urban soils are also a useful place to lock up carbon and, again, we don't want it to move out of the system. So Nick and Luke conclude that non-composted additions are probably better to add to soils. However, they are quick to point out that doing these experiments at larger scales (like a backyard) are important before we read too much into the results. So I'll go on adding the lawn clippings to my garden soil in the meantime while knowing that acting locally really may be affecting globally!

15 November 2011

Darwin down on the farm

To Darwin, agriculture was a vital source of evidence for evolution and for natural selection. One area where Wallace disagreed with Darwin was in how useful agriculture was in explaining evolution. Wallace thought that the comparison was not very close nor was it very effective whereas Darwin devoted much space to it in the Origin. In many ways Wallace was proven correct as evolution has been only a bit player in agriculture over the last 150 years. Until now. A new book, Pragmatic Evolution: Applications of Evolutionary Theory edited by Also Poiani, is due out in December and looks at where evolution is helping to understand the world around us in a practical sense. One of those areas in in agriculture. One of the chapters, Evolution in agriculture, is written by Steve Wratten (Lincoln University) with a former student Mark Gillespie and colleague Aldo Poiani. In this chapter they review how understanding evolution is transforming what we know in the area of agroecology. Steve points out that most agricultural activities attempt to halt evolutionary processes, trapping ecosystems in a state which produces consistent crops and so on. Much evolutionary conflict comes from this including resistence to insecticides, reducing diversity in communities,and removing natural predators and competitors. Taking an evolutionary approach allows us to build more natural and sustainable agricultural ecosystems. In the chapter Steve explains how an evolutonary approach is vital for agriculture to move forward. Hopefully this is the start of evolution regaining its natural place in this most human of endeavours and that Darwin is welcomed down on the farm.

14 November 2011

What they will be doing this summer

Every summer the Department of Ecology offers summer scholarships to undergraduates to get a taste of research (and to be paid for 10 weeks doing it). It's a great way to figure out if this research lark is for you, to make contacts and to meet staff and postgraduates. This year we welcome a number of students who will be calling the department home for the summer.

Gerrit Roux is working on Using morphological and molecular approaches to determine the diet of ground beetle candidates for translocation to Quail Island with Stephane Boyer and Mike Bowie.

Maree Henderson-Fitzgerald is working on the Styx Living Laboratory with Kelly Walker.

Also at the Styx is Chris McClure examining the Effectiveness of a predator-proof fence for conserving lizard fauna in the Styx Catchment with Kelly Walker.

Cathy Mountier will work on the establishment of a monitoring programme for the Punakaiki Coastal Ecological Restoration Project with Mike Bowie.

Ben Wiseman will work with Kelly Walker to enhance and update the Entomological teaching collection.

Marie MacDonald will balance on cliff edges with abundance, behaviour and distribution of the Mt Somers bluff weta – Life on a precipice working with Mike Bowie.

Denise Ford will test a range of rodent traps and baits for species selectivity, bycatch, and animal ethics with Mike Bowie.

Finally, Ceridwin Benn will examine microbrial species compistion in possum bites as a means of identifying individuals with James Ross, Adrian Paterson and Rob Cruickshank.

Good luck and happy researching to these students! We'll find out how it all went next March.

01 November 2011

Of questionable character

It is almost election time here in New Zealand. This year we have been spared much of the usual hoo hah because of the recent (and spectacularly successful) Rugby World Cup dominating the news as well as the Canterbury earthquakes before that. One of the tasks that we will have on Election Day is to find out what New Zealanders think of our voting system. We moved away from a winner takes all 'first past the post' system 15 years ago but there is a move to bring this back. The problem with 'first past the post' is that you can become the government despite winning less than half the overall vote, and once you are in you can act as if you won 100%. Other systems encourage representation in proportion to the amount of votes you won. What has this to do with ecology? Well it turns out that there are similar issues when it comes to analysing large molecular data sets. Such data sets can tell us about the evolutionary history of a group of species; who is related to who and when their last common ancestor lived. The problem is that most of the methods for finding these patterns tend towards the first past the post ideal. The evolutionary tree is built from the strongest signal and other signals are ignored.

Rob Cruickshank has explored the issue of character conflict within molecular data sets in a recent issue of Zootaxa. Ideally, your data set would contain one signal, that of the evolutionary history of a group. Unfortunately there are a number of factors that can introduce other signals, such as convergence, parallel evolution, human error, high rates of change and so on. So within your data set there are usually competing signals, much as within society there are competing political parties. Most analyses simply find the signal with the most votes and this is proclaimed the winner. However, Rob points out that there are several ways to find smaller strength signals to further analyse, after all one of these might be the true answer of how species are related. For example, the fantastically named spectral analysis looks at each signal in the data and shows how much support there is (how many characters agree with this signal) and what conflict they have (how many characters disagree with this signal). Sometimes the signal with the greatest support has a lot of conflict whereas the next largest signal has none. Given that we might expect the correct phylogentic signal to have little conflict then this might encourage us to look further than the loudest signal. This would be like being given two votes: one for the person/party that you wanted to support and one for the person/party that you especially didn't want. If the leading candidate is also the one with the largest conflict then maybe they are not as good for consensus politics as the next candidate with a much lower conflict score. Certainly, in the world of species relationships determined by molecular characters, this might be something worth considering.