It's the Size that Matters: Plant Productivity is Impacted More by Age Than Climate

It turns out that the size and age of a plant may have more to do with their productivity than the environment that they're in. The findings could have implications for carbon capture and storage using plants.

"A fundamental assumption of our models for understanding how climate influences functioning of ecosystems is that temperature and precipitation directly influence how fast plants can take up and use carbon dioxide," said Brian Enquist, one of the researchers, in a news release. "Essentially, warm and wet environments are thought to allow plant metabolism to run fast, while cold and drier environments slow down metabolism and hence lower biomass production in ecosystems. This assumption makes sense, as we know from countless experiments that temperature and water control how fast plants can grow. However, when applied to the scale of entire ecosystems, this assumption appears to not be correct."

In order to learn a bit more about plant productivity, the researchers combined a new mathematical theory from data from more than 1,000 forests across the world. The theory assessed the relative importance of several hypothesized drivers of net productivity. The scientists then tested the theory by using a massive dataset.

In the end, it turns out that plant size and plant age control most of the variation in plant productivity. This flies in the face of previous assumptions that temperature and precipitation were main drivers.

"This general relationship shows that climate doesn't influence productivity by changing the metabolic reaction rates underlying plant growth, but instead by determining how large plants can get and how long they can live for," said Sean Michaletz, lead author of the study. "This means that plants in warm, wet environments can grow more because their larger size and longer growing season enable them to capture more resources, not because climate increases the speed of their metabolism."

The findings reveal a bit more about the relationship between climate and plant biomass. This could help scientists better predict how ecosystems will change with climate conditions.

The findings are published in the journal Nature.