?What do we know about how plants adapted to extreme climates in the desert regions of our world? And how are these plants going to respond to emerging threats, such as increases in aridity, grazing pressure and desertification?
These are the questions that a group of 120 scientists from 27 countries asked when they embarked on a large-scale international study to understand how plants found in drylands have adapted to these extreme habitats.
The unexpected answers to these questions were published in the journal Nature recently, in an article titled “Unforeseen plant phenotypic diversity in a dry and grazed world".
Drylands are areas which face great water scarcity (with an average annual rainfall of 150 to 250mm) and include sub-humid, semi-arid, arid and hyper-arid ecosystems such as the Mediterranean landscape, steppes, savannahs and deserts. Drylands cover 45% of the Earth's terrestrial area and are home to a third of the global human population.
Yet even though an estimated two billion people rely on these drylands for their livelihoods, comparatively few studies have explored how plant diversity in these areas have adapted to extreme climates.
Prof. Thulani Makhalanyani from Stellenbosch 肆客足球's Department of Microbiology and the School for Data Science and Computational Thinking was part of the team which, over the past eight years, have collected samples from several hundred dryland plots across six continents. This collection enabled the analysis of over 1 300 sets of observations of more than 300 plant species, a first on this scale.
The scientists generated a total of 1347 full sets of trait observations for analysis. Particular attention was paid to the characterisation of the plant elementome, that is, the diversity of chemical elements and trace elements (such as nitrogen, phosphorus, calcium, magnesium and zinc) found in plants, as these often-unrecorded traits exert a strong influence on how the latter function. Overall, the study involved more than 130 000 individual plant trait measurements.
They found that plants in arid zones adopt many different adaptation strategies and that, surprisingly, this diversity increases with aridity levels. In other words, above a certain threshold, there was an 88.1% increase in plant trait diversity.
According to an international media release published on EurekAlert, the isolation of these plants (called “plant loneliness syndrome") in more arid zones would appear to have reduced competition between species, allowing them to express a diversity of forms and functions that is globally unique, displaying double the diversity found in more temperate zones. This adaptive diversity could also reflect complex evolutionary histories dating back to the initial colonisation of terrestrial habitats by plants more than 500 million years ago, when these habitats presented extreme conditions for living organisms.
These important zones are now directly threatened by increases in aridity, grazing pressure and desertification. Scientists need to understand how plants respond to such pressures before they can establish the possible future evolution of these fragile ecosystems in terms of biodiversity and functioning.
Prof. Makhalanyane says they are excited to finally see the results of the study in print: “This project has provided remarkable insights regarding functional diversity in understudied deserts, including sites on our continent."
On the photo above: A lonestanding quiver tree (Aloe dichotoma) on a farm in the vicinity of Springbok, Namaqualand, Northern Cape. Image: Alexey Yakovlev, Creative Commons Attribution-Share Alike 2.0 Generic license.
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