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Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/29/2008 Publication Date: 6/15/2009 Citation: Blumenthal, D.M. 2009. Carbon Addition Interacts with Water Availability to Reduce Invasive Forb Establishment in a Semi-arid Grassland. Biological Invasions 11:1281-1290. Interpretive Summary: Increases in nitrogen (N) availability can favor fast-growing invasive species over slow-growing native species. One way to reduce N availability is to add C to the soil, which can induce microbes to take up plant-available N, and reduce the success of invasive species. This method has been used, with widely varying degrees of success, to both study and control plant invasions. One reason that C addition might not work as expected is that N is not always the limiting resource for plant growth. For example, if plant growth is limited by water availability, changes in N availability might have little effect on invasion. Here I ask whether effects of C addition on N availability, resident plant biomass, and invasion depend on water availability in semi-arid mixedgrass prairie. Six invasive species were seeded into plots treated with water (no added water or added water) and/or N (+C, control or +N). Carbon but not N addition had strong effects both with and without added water. Carbon addition reduced available N by an average of 73%, and reduced biomass of resident species from 336 g/m2 to 203 g/m2. Only three seeded species successfully invaded the experiment, and those species only invaded plots with added water. Given added water, C addition reduced biomass of diffuse knapweed by 95%, and prevented invasion by baby’s breath and Dalmatian toadflax. Mechanisms by which C addition reduced invasion varied by species, with added C reducing the growth of individual C. diffusa plants, but reducing numbers of G. paniculata and L. dalmatica individuals. Technical Abstract: Increases in nitrogen (N) availability can favor fast-growing invasive species over slow-growing native species. One way to reduce N availability is to add labile C to the soil, which can lead to microbial immobilization of plant available N, and reduce the success of invasive species. This method has been used, with widely varying degrees of success, to both study and control plant invasions. One reason that C addition might not work as expected is that N is not always the limiting resource for plant growth. For example, if plant growth is limited by water availability, changes in N availability might have little effect on invasion. Here I ask whether effects of C addition on N availability, resident plant biomass, and invasion depend on water availability in semi-arid mixedgrass prairie. Six invasive species were seeded into plots treated with a factorial combination of water (ambient or added) and N (+C, control or +N). Water was added in both the winter, using snow fences, and the summer, using irrigation. Nitrogen addition plots received 2.63 g•m-2 of N, as ammonium nitrate fertilizer, in each of two years. Carbon addition plots received a total of 2948 g•m-2 of dextrose (1167 g•m-2 of C). Carbon but not N addition had strong effects both with and without added water. Carbon addition reduced capture of mineral N by resin probes by an average of 73%, and reduced biomass of resident species from 336 g•m-2 to 203 g•m-2. Only three seeded species successfully invaded the experiment, and those species only invaded plots with added water. Given added water, C addition reduced biomass of Centaurea diffusa (diffuse knapweed) by 95%, and prevented invasion by Gypsophila paniculata (baby’s breath) and Linaria dalmatica (Dalmatian toadflax). Mechanisms by which C addition reduced invasion varied by species, with added C reducing the growth of individual C. diffusa plants, but reducing numbers of G. paniculata and L. dalmatica individuals. |
