Let’s talk about dirt: soil ecology hikes at the Cary Institute

MILLBROOK — A crowd of nearly 30 went undeterred by cool rain for a hike and lecture on soil ecology at the Cary Institute Sunday morning, Sept. 29.

Jane Lucas, who holds a doctorate in ecology and evolutionary biology, led the group on a brief hike in the frigid mist and discussed her research focus: microbial communities.

Lucas said scientists have started to look more closely at soil. In the past, soil science was largely focused on agriculture. The main concern of practitioners and academics were improving yield and reliability of crop harvests and grazing. Now, Lucas said, there is more study on soil’s role in the environment as a whole, and as it’s own environment.

That’s Lucas’s research focus at the Cary Institute. She said soil is host to trillions of microbial critters that are responsible for turning dead leaves and branches into dirt, plus about a million other critical things. “In a spoonful of dirt there are more microbes than people on the planet,” Lucas said to the crowd, sheltered in Cary’s carriage house to escape the drizzle.

Soil microbes are microscopic critters like bacteria, viruses, fungi and algae, and they’re essential in making dirt do what it does best: grow things. They break down organic matter, making nutrients and minerals available in the soil for plants to use.

Soil microbes also bear a lot of responsibility for carbon fixing. When a plant absorbs carbon dioxide from the air it breaks it down and releases oxygen, storing the carbon for use in food. Up to 30% of that carbon is then excreted from the plant’s roots into the soil in substances called exudates, Lucas said. The microscopic critters in the dirt feed on the exudates, locking the carbon in the soil and keeping it out of the atmosphere. The rest of the carbon that’s stored in the plant makes it into the soil when the plant dies and decays.

Microbiomes are diverse and soil conditions have a huge impact on their composition and health. Lucas has been studying the effects of climate change on soil ecology. Experiments at the Cary Institute are testing how elevated soil temperatures, varying pH levels and drought affect microbiome performance. Lucas said microbiome health has huge implications for the health of plants and animals in an environment, and the impacts of climate change have the potential to impact soil ecology negatively.

Lucas made a point to emphasize a holistic view of soil ecology. She gave phosphorous as an example. Phosphorous is a key nutrient to plant health, but most of the phosphorous on Earth is locked in hard rocks below the surface. However, Lucas said, the sands of the Sahara desert contain a lot of stored phosphorous. Winds and currents carry this phosphorous rich sand across the pacific ocean to South America, where it supplies the Amazon rainforest with phosphorous for its lush vegetation. Even when it isn’t traveling thousands of miles across an ocean, dirt is an essential part of our environment, and inextricably linked to to agriculture and public health, Lucas said.

Cary Institute hosts regular lectures hosted by its researching scientists and associates. More information and upcoming events can be found at www.caryinstitute.org/events.