Not All Trees Are Created Equal in Carbon Storing Matters

Eucalyptus Tree

Australian researchers found forests located on nutrient-depleted soils have lower carbon storing capabilities than estimated. Photo: Australian Eucalyptus tree (Eucalyptus bridgesiana).

A new study suggests that not all trees are equally good at absorbing carbon dioxide. Researchers at the Western Sydney University found that Australia’s Eucalyptus trees might need more nutrients to boost their carbon storing capabilities.

The study was published this week in the journal Nature Climate Change.

The study results could alter the models used by climate scientists worldwide. Many of those models are based on the belief that CO2 fertilizes trees, which helps them grow and store more greenhouse gas emissions.

Lead author Prof. David Ellsworth noted that science heavily relies on climate change modelling to predict the amount of emissions offset by the world’s trees. However, most models are flawed because they include data on forests growing at temperate latitudes where nutrients are readily available. This means that many of the models do not take into account nutrient shortages and reduced carbon absorption capabilities of forests in other parts of the world.

It is worth noting that tropical and subtropical forests are located on nutrient-depleted soils, which suggests their ability to capture CO2 is significantly lower than the levels produced by computer models. So, global estimates on trees’ capacity to store carbon may be exaggerated.

In their study, Australian researchers exposed large swaths of eucalyptus forest to higher levels of CO2 emissions. During the experiments, the CO2 levels reached 550ppm, which is 150 ppm higher than normal levels.

In other parts of the world, including the U.S. and Europe, researchers performed similar experiments on temperate forests, which in the wake of the treatment, experienced a boost in their pace of growth of 23 percent.

In Australia, however, researchers noted that elevated CO2 levels boosted the rate of photosynthesis by up to 19% over three years, but there was no change in the growth rate of wood, leaves, and stems. When the research team added extra nutrients such as phosphorus to Eucalyptus trees’ soil, they noticed that the growth rate jumped 35%. Scientists estimate that within three or five decades, carbon dioxide levels could hit or go beyond the 550 ppm threshold.

Ellsworth pointed out that in greenhouses, many carbon-loving crops such as cucumbers, tomatoes, and cut flowers grow faster, stronger and have more fruit if they are given extra carbon. When it comes to Australia forests, things are different because the soil is very old and low in nutrients.
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