The ability of tropical forests to grow and store carbon is limited, in part, by herbivory. Insects and other animals prefer to feed on nitrogen-fixing trees, reducing the success of fixers and the nitrogen they provide.
The ability of tropical forests to grow and store carbon is limited, in part, by herbivory. Insects and other animals prefer to feed on nitrogen-fixing trees, reducing the success of fixers and the nitrogen they provide. So reports a new paper out this week in the journal Nature, which recommends accounting for herbivory constraints on nitrogen-fixing trees in climate models and projections of the tropical forest carbon sink.
By partnering with soil microbes, nitrogen-fixing trees turn atmospheric nitrogen gas into a form of nitrogen that is available to plants. When fixers shed their leaves, they enrich soils with nitrogen, benefitting nearby plants. In nitrogen-poor tropical forests, nitrogen-fixing trees are the main source of new nitrogen to soils. Yet they are also rare.
Sarah Batterman, a Tropical Forest Ecologist at Cary Institute of Ecosystem Studies and co-author on the paper, explains, “Tree growth in many tropical forests is limited by lack of nitrogen. Given the substantial benefit of nitrogen to these forests, it has long been a mystery why nitrogen-fixing trees represent just 5-15% of trees. We suspected that herbivores might be preferentially targeting fixers due to their nutritious, nitrogen-rich leaves.”
Read more at: Cary Institute of Ecosystems Studies
Nitrogen-fixing trees can fertilize the soil with the help of partner bacteria. It has remained a puzzle why these trees do not become more prevalent in nitrogen-poor tropical forests. This study suggests that herbivory by animals may be the answer. (Photo Credit: Sarah Batterman)
