A new study led by Andrew Baldwin, professor of wetland ecology in the Department of Environmental Science and Technology and colleague Kai Jensen at University of Hamburg (Germany), has looked at how atmospheric temperature, as is occurring due to global warming, may affect the growth and diversity of tidal freshwater wetland plants in Europe and North America.
Titled “Warming increases plant biomass and reduces diversity across continents, latitudes, and species migration scenarios in experimental wetland communities,” the study is in press in Global Change Biology, a leading international journal that focuses on how current environmental change affects biological systems over a substantial part of the globe.
For their relatively small size in the landscape, wetlands are disproportionately more important than terrestrial or aquatic ecosystems for a suite of ecosystem functions and services, including plant and animal habitat, water quality improvement, and carbon and nitrogen cycling and processing.
“We created communities grown from tidal freshwater wetland seed banks and exposed them to current temperatures and warmer temperatures, about 3 degrees C higher, in the greenhouse and looked at the effects of warming on the plant growth and number of species in experimental trays,” explains Dr. Baldwin. During this study, he and Dr. Jensen, with graduate student Marisa Schönfeldt, mixed seed bank samples from different latitudes together to simulate how migration of species from warmer into cooler climates caused by increased warming might affect plant growth and diversity.
Dr. Baldwin and colleagues used wetland plants grown from buried seeds in wetland soils collected at different latitudes on the European and North American coasts of the Atlantic Ocean. “Some of the important species included were Lythrum salicaria (purple loosestrife), Bidens spp. (bur-marigold, beggar’s ticks), Agrostis stolonifera (creeping bentgrass), Polygonum spp. (smartweeds), Phalaris arundinacea (reed-canary grass) and Leersia oryzoides (rice cutgrass).”
The team’s research found that biomass in warmed greenhouse rooms was higher than in ambient temperature rooms, but the diversity of species was lower. “Mixing together to simulate species migration from warmer to cooler climates increased the number of species by 60 to 100%, but this did not result more plant growth,” says Dr. Baldwin. These findings could mean that warmer temperatures may lead to more plant growth in the future in temperate tidal freshwater wetlands but plant diversity will decrease unless offset by migration of species from warmer latitudes. These experimental findings broadly indicate that warming is likely to influence the vegetation-related ecosystem functions of freshwater wetlands.