What is it about?
Increasing atmospheric CO2 concentrations ([CO2]), temperatures and droughts are affecting tropical regions. Individually, the effects of these climate factors on plants are well-known but the interactive effects of a combination of factors are not as well studied. We hypothesized that these environmental conditions will have varying impacts on plants along a forest-savanna gradient. In a glasshouse experiment, we raised seedlings of three Eucalyptus species, each occurring naturally in a wet forest, savanna and forest–savanna ecotone, respectively. We evaluated the effect of drought, elevated temperature (4 °C above ambient glasshouse temperature of 22 °C) and elevated temperature in combination with elevated [CO2] (400 ppm [CO2] above ambient of 400 ppm), on seedling growth, survivorship and physiological responses. Elevated temperature under ambient [CO2] had little effect on growth, biomass and plant performance of well-watered seedlings, but hastened mortality in drought-affected seedlings, affecting the forest and ecotone more strongly than the savanna species. In contrast, elevated [CO2] in combination with elevated temperatures delayed the appearance of drought stress symptoms and enhanced survivorship in drought-affected seedlings, with the savanna species surviving the longest, followed by the ecotone and forest species. Elevated [CO2] in combination with elevated temperatures also enhanced growth and biomass and photosynthesis in well-watered seedlings of all species, but modified shoot:root biomass partitioning and stomatal conductance differentially across species.
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Photo by jasper wilde on Unsplash
Why is it important?
Drought, fire and increased temperature will affect both natural environments and agricultural landscapes, yes, we have little information on how all these interactive factors will affect vegetation. Our study highlights the need for a better understand of the interactive effects of elevated [CO2], temperature and drought on plants and the potential to upscale these insights for understanding biome changes.
Perspectives
The seedling stage is the most vulnerable life stage of any plant, and testing seedling responses and survival in a glasshouse study can give us good insights on how plant populations will survive. Still, we will also need field studies.
Dr David YP Tng
School for Field Studies
Read the Original
This page is a summary of: Elevated temperature and CO2 cause differential growth stimulation and drought survival responses in eucalypt species from contrasting habitats, Tree Physiology, November 2019, Oxford University Press (OUP),
DOI: 10.1093/treephys/tpz095.
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