Biomass Production and Temporal Stability Are Similar in Switchgrass Monoculture and Diverse Grassland

Research into herbaceous bioenergy production has focused on identifying grassland systems that are both productive and temporally stable, where stability equals the ratio of mean biomass production to its temporal standard deviation. The question remains as to effects of community properties, including species richness, on temporal stability. We compared aboveground net primary productivity (ANPP) and the temporal stability in ANPP of unfertilized grassland planted either as a mixture of native perennial grass and forb species or monoculture of Panicum virgatum L. (switchgrass) in Texas, USA. ANPP varied in response to inter-annual variation (IAV) in precipitation. The precipitation effect on ANPP stability was mediated through two components of the influence of a single community property, community (species-abundance) weighted values of leaf dry matter content (LDMC), on productivity. These components include community LDMC and ANPP-LDMC regressions. Stability was similar between vegetation types but was regulated by different components of the LDMC effect on ANPP in mixture and switchgrass. Temporal stability in mixture depended mainly on ANPP variation that resulted from change in community LDMC. Stability of switchgrass depended primarily on ANPP variation that resulted from precipitation-caused change in ANPP-LDMC regressions. Stability declined as ANPP increased in mixture because LDMC variation increased when productivity was high. We find that ANPP and ANPP stability can be as great in an unfertilized planting of a switchgrass monoculture as diverse mixture of grassland species. Similar levels of stability can be achieved via different components of the LDMC effect on productivity.