Scientists have discovered that a particular kind of carbohydrate may help tropical trees survive drought conditions, adding to our understanding of how we might help support our rainforests as we face the challenges of global warming.
The study, which was published late last month in the journal Nature Climate Change, saw an international team of scientists, including researchers from the University of Oxford, plant 1,400 saplings, this group being made up of 10 different tropical tree species. The scientists wanted to investigate if restricting the trees’ ability to generate non-structural carbohydrates (NSC), which appear to play a part in keeping trees hydrated, would lead to the trees dying more quickly.
To discern this, the scientists raised one group of the saplings in dark conditions before exposing them to sunlight. The second group underwent the reverse, growing in sunlight before being exposed to dark conditions. Of course, plants need sunlight to photosynthesize and sustain themselves with chemicals and compounds like the NSCs. As a result, the second group had significantly lower NSC levels than the first.
After this, the scientists exposed both groups to drought-like conditions. What they found was that the saplings which were raised in the dark and, as a result, had lower NSC levels, died more quickly of desiccation, that is to say that they dried out, when compared to the first group which had normal NSC levels.
This research is part of a wider effort to assess just how well the world is doing with its conservation efforts in the Borneo rainforest and, as part of that, if the forests will be more susceptible to climate change as a result of deforestation. The research wanted to know whether different species had different NSC levels, and if so would that make them more or less resilient to drought conditions. The researchers now know this to be true, at least in some cases, and this helps to explain why certain tree species fair better under more dry and arid conditions.
Co-author of the study Andrew Hector, from the University of Oxford’s Department of Plant Sciences, believes that the different levels of NSCs “probably play an important role in defining their different ecological niches.” Why does this matter? There are a couple of reasons.
First, it might allow us to identify which areas of forest are more likely to suffer under drought conditions. That means we can concentrate efforts to keep the forests alive in those particular areas first, confident that the other areas of the forest which contain plants with higher NSC levels can probably manage on their own for a while.
Secondly, Professor Hector seems to think this discovery could help us to regrow our forests. The Borneo rainforests, like many, have suffered intense deforestation in the past few decades. Now, efforts are underway to regrow those forests but these efforts usually use only or two species of trees. The theories behind this are diverse but can include that it will cut competition among tree species, and that it’s also usually cheaper. However, this doesn’t take into account the wider ecosystem and how the different varieties of trees might have helped sustain the rainforest. By planting species of all one kind, and so potentially all with low NSC levels, the forests we’re regrowing might be vulnerable should drought conditions worsen, something that many climate models predict. The solution, then, is planting different species of trees.
“Diverse mixture of plants means you are spreading the risk,” Hector is quoted as saying. “Although you might lose your vulnerable species, you still have resilient ones in there so the forest maintains its function.”
Lastly, scientists can take this information and begin to predict which forests might be particularly vulnerable, and just how vulnerable they will be, as we face the temperature rises that climate change promises to impose. We have various models for different levels, so scientists in theory at least could begin to estimate how much of our forests are under threat, and how by diversifying the species, we could help ensure that our forests are more hardy when those conditions do eventually arrive.
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