Effects of plant species on macrophyte decomposition under three nutrient conditions in a eutrophic shallow lake, North China

Macrophyte decomposition can significantly influence aquatic carbon and nutrient cycling, especially in eutrophic shallow lakes, in which incomplete decomposition of detritus may lead to sediment accumulation and accelerate lake aging. In order to explore the role of macrophyte decomposition in lake terrestrialization, six major aquatic plants (two submerged, two floating, and two emergent species) in Lake Baiyangdian were investigated in this study. Detritus of these species were placed at three sites with different pollution intensities to investigate the contributions of plant species, site nutrient condition, and their interactions on detritus decomposition. Detritus decomposition was represented by detritus mass remaining at each sampling time. Results of this study suggest that although decomposition processes are species and site specific, and the effects of species are stronger than site conditions. Initial detritus phosphorus (P)-related indicators were proved to be effective controllers for detritus decay at the later stage of the experiment. Significant interactions between site and species indicate that plant species also influenced site controls on detritus mass loss. Site effects on decomposition were significant for submerged and floating species (P < 0.01), and slightly significant for emergent species (P < 0.05). A mathematic two-stage decomposition model was developed based on the experimental results using stepwise analysis to analyze effects of detritus quality and site conditions on decomposition. The detritus quality indicators were the main contributors for both early and later stages of detritus decomposition, while the site nutrients only affected decomposition at the later stage.

► Macrophyte decomposition rates are species and site specific.
► Plant species is the main determinant of detritus mass loss.
► Influences of initial detritus quality indicators on detritus mass loss increase with time.
► The effect of site conditions on detritus mass loss vary with plant species.