The invasive grass Agropyron cristatum doubles belowground productivity but not soil carbon

• Published in: Ecology (Durham) Vol. 92; no. 3; pp. 657 - 664
• Main Authors: Macdougall, Andrew S, Wilson, Scott D
• Format: Journal Article
• Language: English
• Published: Washington, DC Ecological Society of America 01-03-2011
• Subjects: Agropyron - physiology; Agropyron cristatum; Animal and plant ecology; Animal, plant and microbial ecology; belowground production; Biological and medical sciences; Biological invasions; C3 plants; Carbon; Carbon - chemistry; carbon nitrogen ratio; carbon sequestration; Ecological invasion; Ecosystem; Ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; grass; Grasses; Grassland soils; Grasslands National Park (Canada); indigenous species; Introduced Species; invasion; invasive species; Isotopes; Mortality; Nonnative species; Plant Roots - physiology; prairie; Prairie soils; Productivity; rhizotron study; root productivity; roots; soil; Soil - chemistry; Soil ecology; Soil Microbiology; Soil water; Time Factors; tissue quality; Tissues; Vegetation; Canada; North America; America; Grassland; Productivity; Monocotyledones; Grasslands National Park (Canada); Root; tissue quality; Carbon; Carbon sequestration; Invasion; prairie; National park; Soils; belowground production; Gramineae; Quality; grass; Angiospermae; Spermatophyta; Herbaceous plant; rhizotron study; Agropyron cristatum; root productivity
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/10-0631.1

Root dynamics are among the largest knowledge gaps in determining how terrestrial carbon (C) cycles will respond to environmental change. Increases in productivity accompanying plant invasions and introductions could increase ecosystem C storage, but belowground changes are unknown, even though roots may account for 50-–90%% of production in temperate ecosystems. We examined whether the introduction of a widespread invasive grass with relatively high shoot production also increased belowground productivity and soil C storage, using a multiyear rhizotron study in 50-year-old stands dominated either by the invasive C
3
grass
Agropyron cristatum
or by largely C
4
native grasses. Relative to native vegetation, stands dominated by the invader had doubled root productivity. Soil carbon isotope values showed that the invader had made detectable contributions to soil C. Soil C content, however, was not significantly different between invader-dominated stands (0.42 mg C/g soil) and native vegetation (0.45 mg C/g soil). The discrepancy between enhanced production and lack of soil C changes was attributable to differences in root traits between invader-dominated stands and native vegetation. Relative to native vegetation, roots beneath the invader had 59%% more young white tissue, with 80%% higher mortality and 19%% lower C:N ratios (all
P
< 0.05). Such patterns have previously been reported for aboveground tissues of invaders, and we show that they are also found belowground. If these root traits occur in other invasive species, then the global phenomenon of increased productivity following biological invasion may not increase soil C storage.