Climate change predictors
Facilitator: Andy, thank you for joining us. Now I'm told that when it comes to plants and leaves, you're daring to go where nobody else has gone before. Tell me a little bit about what you're studying.
Andy:: The daring to go where no one else has gone before comes in when you think that physics has long predicted why leaves should be hot or cold and there's lots of really good reasons why that should happen if we think about leaves as metal plates, but there are a number of reasons why leaves are not metal plates and they're very, very difficult to measure. So I guess I'm looking at all the reasons why leaves should be different temperatures, but I'm looking at real leaves instead of metal plates.
Facilitator: So why is finding out about leaf temperature so important?
Andy:: Temperature is important for physiological reasons. As living things we require a certain temperature to function. Just like humans that need to function at their 35 degrees, for plants to photosynthesise they need to maintain a certain temperature, but they can't get too hot because if they get too hot they're physiological equipment gets damaged and they die and this tends to happen if they get too hot too many times.
Facilitator:So how does this research then help us predict some of the impacts that climate change may have?
Andy:: If we think about climate change in Australia for example, we're not just predicting increased averages, we're predicting increased extremes, so extreme temperature spikes so more in number and more in intensity. So if a leaf repeatedly goes into those extreme temperature spikes, then it's dead. I guess I'm interested in which leaves out there are going to survive and which aren't.
Facilitator: So in some way this is another research tool to help us understand more about how climate change may affect us?
Andy:: Yeah, I'm interested to see which plants with which leaf types are going to survive in extreme temperature events. So if we have a big diversity of plants in some seasons, particularly which of those plant species - maybe there's a hundred species in a square kilometre - which of those plant species are going to survive in the future and which aren't. By looking at leaf characteristics and how they respond to temperature, this might give us a predictive tool, if you like, about what's going to happen to Australian plant diversity in a changed climate.
Facilitator: It really brings home that concept that you learn in high school about leaves being alive, doesn't it?
Andy:: Yes, well they definitely are alive and although they, strictly speaking, don't behave, they do respond and leaves are where photosynthesis happens and photosynthesis is primary productivity, it's what we eat. The products of photosynthesis are what we eat, the sugars that keep us all alive. So if leaves die, we die. So it's kind of important to understand that.
Facilitator:So this is a good point for us to get a better understanding from you about what we know about how leaves behave and what you're discovering.
Andy:: We think we know how leaves should respond based on physical theory, but we don't actually have many measurements of how leaves respond out there in the field. You can look at a replica of a leaf and how it responds with temperature changes, but it doesn't have the water in it and it doesn't have the holes in it and it isn't covered with hairs and it isn't angled in a different way around a plant, it's not subject to self-shading. So I'm interested in seeing whether we can take what we think should happen, based on the perfect leaf, and see whether that's actually happening in the world. But when you look at the diversity of leaves out there, I predict that there’s going to be a lot of differences and probably differences that we haven't yet come across and in ways that we don’t understand yet.
Facilitator: So I imagine that means you get to do some pretty exciting field research.
Andy:: Yeah, on a shoestring. I'm very interested in extreme environments. I love seeing plants surviving where we find it tough to survive. I'm just about to go out to the semiarid region in very far western New South Wales where I predict it's going to be in the upper 30s to upper 40s. I'll be finding it tough but the plants out there are surviving. I like to go out there in the toughest conditions and see what leaves are doing and I do this by taking out various bits of equipment to measure leaf temperatures under different conditions.
Facilitator: So then tell me about the equipment and the technology you'd be using.
Andy:: There's various ways you can measure leaf temperature. The standard way and still a very good way is by using thermocouples, little wires that you put on the underside of the leaf, the shaded side of the leaf. You can keep the thermocouple there during the day and monitor temperature changes with environmental influences in real time. You can also use thermal imagery because that gives a complete picture across the leaf. You can actually visualise the way a leaf changes its temperature during the day. That's quite advanced and expensive equipment so I tend to use a little bit of both, depending on access to equipment. But it's really nice to be able to look at leaf temperature in a visual form, so that's why infrared is a nice tool.
Facilitator: So what are the next challenges here for you in your research?
Andy:: My immediate challenge is patience because I want to know it all now and it’s really baby steps. We have to do this in a very methodical way. As you can see, there are so many different types of leaves, you can’t just measure one or two leaves and say that's how they respond. There is different photosynthetic systems that have different rates of water loss which is going to change the way temperature is held in a leaf or heat is held in a leaf. I guess the challenge is getting enough species' measurements out there so that we can start to pick up patterns and make generalisations, 'cause at the moment we can't do that.
Facilitator: Well Andy, that all sounds pretty exciting. Good luck and it also sounds like you've got some interesting challenges ahead.
Andy:: I think so but I'm into it, so that's the main thing.
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