Biodiversity, photosynthetic mode, and ecosystem services differ between native and novel ecosystems

Authors: MARTIN, LEANNE - Iowa State University; Polley, Herbert; DANESHGAR, PEDRAM - Monmouth University; HARRIS, MARY - Iowa State University; WILSEY, BRIAN - Iowa State University

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2013
Publication Date: 6/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59495
Citation: Martin, L.M., Polley, H.W., Daneshgar, P.P., Harris, M.A., Wilsey, B.J. 2014. Biodiversity, photosynthetic mode, and ecosystem services differ between native and novel ecosystems. Oecologia. 175:687-697.

Interpretive Summary: Human activities have contributed to an explosive increase in the abundance of non-native or exotic plant species in grassland regions of the world. Most exotic plants were introduced by humans presumably because they differed from native species in certain traits or growth habits that were deemed desirable. However, it remains debatable whether ecosystem properties and functions of value to humans, such as plant productivity, forage quality, and species diversity, differ consistently between grasslands dominated by native and exotic plants. We found that plant diversity was much lower and forage quality was slightly higher in exotic- than native-dominated grasslands in the tallgrass prairie region of the Great Plains of the USA. Exotic systems were strongly dominated by grasses that grow mostly during either the early season or late season, whereas the relative abundances of early- and late-season grasses shifts gradually along a south-to-north transect in native systems. Grasslands dominated by exotic plants thus lacked the diversity in seasonal growth patterns that characterizes native systems and is important in reducing year-to-year variability in plant. Our results indicate the importance of maintaining or increasing the dominance of native plant species in grasslands as a means to increase the reliability of these systems upon which humans depend for food and fiber.

Technical Abstract: Human alteration of ecosystems has caused non-native plant species with novel ecological interactions to persist on landscapes. It is unknown whether exotic-and native-dominated systems function similarly because studies to date have included few locations and typically assessed impacts of single or few exotic species on one or a few ecosystem services. We tested whether multiple ecosystem services differed between native and exotic grasslands across 42 sites along a latitudinal gradient in the tallgrass prairie region in the central USA, and whether exotic species themselves could cause altered functioning in a controlled field experiment. Here we show that grasslands dominated by multiple exotic plant species had drastically altered ecosystem services and functioning compared to native-dominated systems. Exotic grasslands had lower plant diversity and slightly higher forage quality compared to native-dominated sites. Exotic sites also exhibited a state shift to C4 species at southern and to C3 species at northern latitudes with a tipping point at 36-38 degrees. Large differences in C3:C4 proportions and temporal niche partitioning were found in the experiment, implying that latitudinal differences between native- and exotic-grasslands were partially caused by species themselves. Our results indicate that additions of multiple exotic species are causing system shifts that have important broad-scale impacts.