Introducing the kauri drought experiment

KDE logo - 300 dpi web-01

I’m super excited to reveal my new project logo designed by the amazingly talented Josie Galbraith.  Thanks Josie for creating such a beautiful visual to represent my work. And now, it’s time to science!

Exciting news! PhD scholarships coming soon

I’m super excited about my recent success in the Rutherford Discovery Fellowship scheme. The grant is worth $800K over five years and will allow me to concentrate on my research for that period of time. I will be working on a field-based drought experiment in native NZ forest. I will use throughfall exclusion (similar to this) to create artificially droughted plots and will then explore aspects of the physiology and ecology of the plants and associated biota. The funding includes two PhD scholarships. These will be open to  domestic and international students. If you are interested, please get in touch (via my University of Auckland email address).

Interested students should be specific about their expertise and interest in drought research. Skills in plant ecophysiology, modelling, soil science, forest ecology, fluxes of carbon and water and forestry are particularly desirable. At this stage, I’m hoping one of the students can start in early 2016 with another starting later in 2016 or early 2017. I will post more information as it becomes available.

The Paturoa Kauri FAQ

On Monday morning (9th March 2015) locals, conservationists and tangata whenua gathered at 40 Paturoa Road to protect a centuries old kauri tree marked for felling to make way for new dwellings on the property. Thanks to the efforts of these dedicated folk, the trees are safe (for now). So what is so special about this tree and why should we care about it being removed? Here I address several important questions about the value and significance of this tree and the surrounding vegetation.

Why are kauri trees so special?

Kauri are amongst the largest and longest-lived trees in the world. Tree enthusiasts travel from across the globe to see these majestic plants. Kauri have a special place in Maori cultural heritage because they are taonga species. They have an important role in the spiritual beliefs of tangata whenua and are viewed as chiefs of the forest and a living connection to ancestors. They produce beautiful wood that has been used to build houses, boats and carvings and kauri gum was used to make carvings, glue and other products. Sadly, their wood is so prized that around 95-97% of kauri was cleared after European settlement. Kauri are now protected but the new threat of kauri dieback is threatening the remaining individuals.

Is it really 500 years old?

The age of the tree appears to have been estimated. We can estimate the age of a tree using two approaches. The most accurate approach is to count the annual rings accumulated in the trunk as the tree grows. We can also measure the diameter of the trunk and estimate tree age. For some tree species, this has been shown to be a very effective approach but for kauri, it can be inaccurate because there is only a weak relationship between tree age and trunk girth. That said, it is highly likely that the tree is several centuries old. A tree of this size and age supports a range of epiphytes, lichens and mosses in its branches and is therefore valuable habitat for other species. It also stores vast amounts of carbon and is important for binding soil and modulating the water cycle. No matter the age of the tree, it is ecologically significant.

What about kauri dieback?

The Paturoa Road area is known to be heavily infected with kauri dieback with a number of confirmed cases of diseased trees. Reports about the tree in question suggest that it is currently healthy. A well tree in a diseased area may have some form of resistance and therefore has increased ecological value. The tree may be a vital resource for the Scion Research programme looking for resistant trees. If the tree is infected with dieback and is yet to show symptoms, the removal process and management of the site during the building process must consider biosecurity. The pathogen causing kauri dieback is transported in soils and if wood and equipment are not properly disinfected before entering and leaving the site, the pathogen will be further spread. It is not clear if biosecurity tests have been done at the site to check for kauri dieback. This is a vital step, even if the tree was removed.

What has gone wrong here?

Without knowing the internal processes in council, it’s hard to know why this tree has been approved for removal. It is clear that the current legislation is not protecting valuable trees. Where kauri are involved, there should be mandatory biosecurity checks to make sure the site is correctly managed to prevent spread of kauri dieback. Reports suggest there was no iwi consultation. This is unacceptable given the spiritual significance of kauri. Titirangi is famous for its leafy environment and local residents clearly treasure their forest and trees. There needs to be better protection of this unique and beautiful part of Auckland for everyone to enjoy.

What about the rimu?

Other trees and vegetation, including a 300 year old rimu will also be removed from the site. This is also unfortunate but rimu are not currently threatened by dieback. It would be nice to conserve the rimu too but building on bush land will always require the removal of some plants.

The final word

All kauri are living national treasures. In Europe, centuries old buildings are carefully preserved and protected. We don’t have that type of architectural heritage but we do have a rich natural and cultural heritage that forms part of our identity. This heritage must be conserved for the benefit of future generations. Tane Mahuta will not live forever and this tree may be the largest tree centuries from now. In the context of kauri dieback, this tree is particularly valuable. Surely with some clever design, this tree can be saved for future generations. If nothing else, the tree protection laws need to be reconsidered.

Canopy fieldwork = tree climbing fun in the kauri forest

So many things can go wrong in ecoshysiology fieldwork. The main concern is the weather, then there are equipment failures, battery issues, helpers becoming unwell, forgetting gear, the list goes on but we had a close to perfect field trip last week. Here are some photos of our adventures in the field. We were measuring leaf gas exchange (photosynthesis and stomatal conductance) and leaf water potentials of several species in the kauri forest at Huapai Scientific Reserve. We also installed some sap flow sensors at the base of the canopy in our two largest sample trees to complement the sensors at breast height.

Thanks to Dan, Sarah, Jo and Julia for their efforts throughout several long days and a big thank you to Freddie Hjelm from The Living Tree Company and his team, Scotty and Chrissy for their assistance in getting everything happening up above. Some of these photos were taken by Freddie too. Stay posted for some of the results and more photos soon.

There are climbers in each of these trees. Can you spot them?

There are climbers in each of these trees. Can you spot them?

My dirty secret about my latest paper

I have a dirty secret. Actually, it’s not a secret because it’s on twitter which is a public forum so everyone can see it. But I do feel kind of grubby about it and I’ve just worked out why. Last Thursday, I sent this tweet –

Ten lovely people obliged (thank you for playing along @benbondlamberty, @TimCurran8, @PhilJ_Rose,  @HelenWNathan, @PPUAMX, @jcusens, @jmrbrock, @SarahTheWise, @turtleandweasel, @ju*ka, you guys rock) and now my paper is ranked 3rd of 172 for the journal Plant Ecology. I think it’s an important paper because it shows litterfall increases significantly in kauri forest under severe drought. However, I am well aware that I’m completely biased and we haven’t really made any major scientific advances with this work. So now I don’t feel right about manipulating altmetrics scores. As part of this process, one of the retweeters contacted me (probably tongue-in-cheek) and suggested I should tweet about his paper. So I had a look at it and wrote this –

It’s been retweeted 13 times. So for one retweet, my friend has my tweet plus 13 retweets contributing towards his altmetric score. I’d like to think it was my witty take on his paper that scored the retweets. Reality is, it was the universal appeal of their findings. This paper was already in the to 5% of all papers with altmetrics scores so had already proven it’s worth.

I guess that’s why I feel kind of wrong about what I did. Something with wide appeal or super cool results will get attention without the author being so overt. I’m not convinced I have the 3rd best paper in this journal but I do know I have a few fun friends on twitter. I don’t think I’ll be so bold about asking for retweets again. I’d be interested to hear your thoughts on this?

For more on altmetrics and what they tell us, check out this post on the Wiley Exchanges Blog.

And find further reflections on social media stats here.

Let the litter fall! Leaf loss to safe water. Kauri and drought part 2.

During the 2013 drought, the most noticable impact on the kauri forest was the increase in litterfall. It’s well established that many tree species lose their leaves in response to drought, leading to decreased plant water loss. Deciduous trees may lose their leaves early while semi deciduous trees may lose more leaves in a dry year. By reducing leaf area, trees reduce the aarea of water-losing surfaces, thereby reducing overall water loss.

In a recently accepted paper in Plant Ecology, we report that litterfall increased 72% in 2013 compared to 2012 because of dry soil conditions (see figure). Most of the extra litter was kauri leaf and twig material.

Kauri are known to self-prune branches but the reason for branch abscission has been unclear.  It may be that this costly process occurs to protect the highly vulnerable hydraulic system of these forest giants. During dry periods, trees through off twigs to prevent failure of the water conducting system of the plant.

We are doing ongoing monitoring to determine the lag impact of this massive biomass loss to the forest floor.