how do shorter trees survive among tall trees in the forest?
Answers
Explanation:
Forests with canopy heights of around 18 metres are more resistant to the effects of severe drought than those with shorter and taller trees, according to researchers in China and the US.
In the past, studies have disagreed on whether forests with lower or higher canopies will be more likely to make it through prolonged spells of hot, dry weather. The discrepancy has made it difficult for forest managers, who need to know which tree heights to encourage to ensure the highest growth and survival rates during extreme drought.
Study leader Peipei Xu at Beijing Normal University in China and her colleagues believe the issue is increasingly pressing. “Climate data indicate that warm areas of land are increasing, and the warmed areas are also drying,” says Chuixiang Yi at the City University of New York, US. “Hot-dry-induced forest mortality poses a significant global concern for the future as carbon dioxide continues to rise and the climate continues to warm.”
Xu, Yi and the rest of the team aimed to quantify the relationships between canopy height, growth and survival rates during drought accurately for the first time. They analysed data gathered during a severe drought in the southwestern US in 2002 that showed the effect on the ring widths of tree trunks, a useful indicator of their yearly growth. In addition, satellite data revealed how the density of vegetation changed over the course of the drought; the team used this to calculate both leaf growth and tree mortality rates.