Study: Fertilization Destabilizes Global Grassland Ecosystems

February 18, 2014 - News Release

A new study involving a University of Guelph professor and conducted on five continents shows that fertilizing natural grasslands -- intentionally or not – destabilizes global grassland ecosystems.

The study, published Feb. 16 in the journal Nature, marks the first time such a large experiment has been conducted on natural sites. It used a network of natural grassland research sites around the world called the Nutrient Network.

The research team included Guelph’s Prof. Andrew MacDougall from the Department of Integrative Biology. The study was led by Yann Hautier, a Marie Curie Fellow associated with the University of Minnesota and the Institute of Evolutionary Biology and Environmental Studies at the University of Zurich.

The researchers found that plant diversity in natural ecosystems creates more stable ecosystems over time because of less synchronized growth of plants.

“It’s akin to a carpenter building a house with a fully equipped tool chest,” said MacDougall.

“Each tool in the chest can complement the other, with each suited to a specific job. Conversely, building a house with only a hammer, a saw and a chisel is next to impossible, which is analogous to how biodiversity loss decreases the ability of natural systems to provide valued services.”

The researchers collected plants from each site, then sorted, dried and weighed them to monitor the number of species and total amount of plants, or “biomass,” grown over time. They used this information to quantify species diversity and ecosystem stability.

The researchers found that grassland diversity and stability are reduced when fertilizer is added. Fertilizers are intentionally used in grasslands to increase livestock fodder.

Fertilizer is also added unintentionally in many places around the world as nitrogen, a common fertilizer, enters the atmosphere from farming, industry and burning of fossil fuels in automobiles.

Rainfall washes nitrogen from the atmosphere onto grasslands, changing the growth and types of plant species. This study placed measured amounts of fertilizer on a portion of the research sites and measured the ensuing changes.

Hautier said the study shows that “we need to consider not just how productive ecosystems are but also how stable they are in the long term, and how biodiversity is related to both aspects of ecosystem functioning.”

Prof. Andrew MacDougall
Department of Integrative Biology
519-824-4120, Ext. 56570/ 53594

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