Concurrent Effects of Sediment Accretion and Nutrient Availability on the Clonal Growth Strategy of Carex brevicuspis-A Wetland Sedge That Produces Both Spreading and Clumping Ramets

Abstract

Clonal plants producing both clumping and spreading ramets can adjust their growth forms in response to resource heterogeneity or environmental stress. They might produce clumping ramets to retain favorable patches, or produce spreading ramets to escape from stress-affected patches. This study aimed to investigate the rarely reported concurrent effects of sediment accretion and nutrient enrichment, which often occur simultaneously in lacustrine wetlands, on the vegetative propagation and clonal growth forms of Carex brevicuspis C.B. Clarke by conducting a factorial experiment of sediment burial and nutrient addition. Biomass accumulation, new ramet and rhizome numbers, and ramet length of C. brevicuspis were not affected at moderate burial, but were significantly lower after deep burial. Similarly, nutrient enrichment increased the growth and vegetative propagation of C. brevicuspis up to moderate sediment burial, but not after deep burial. Sediment accretion increased the proportion of spreading ramets produced by C. brevicuspis, whereas nutrient addition had no effect on the clonal growth forms. Our results indicated that the plasticity of clonal growth forms is an effective strategy used by plants to acclimate to moderate sediment accretion. Nutrient enrichment did not influence the clonal growth forms of C. brevicuspis and could not facilitate its acclimation to heavy sedimentation condition.

Responses to Sedimentation in Ramet Populations of the Clonal Plant Carex brevicuspis

“…Plant growth of C. brevicuspis populations were significantly affected by both sediment burial and population size, and the biomass accumulation and RGR of C. brevicuspis populations decreased under sediment burial conditions. Under deep burial conditions, our observations were consistent with those of previous studies ( Pan et al, 2012 ; Li et al, 2016 ; Chen et al, 2017 ), which found that C. brevicuspis cannot acclimatize to heavy sedimentation. In this experiment, we did not find the stimulatory effect of shallow burial on plant growth, which has been reported previously by other studies ( Pan et al, 2012 ; Chen et al, 2017 ).…”

“…Under deep burial conditions, our observations were consistent with those of previous studies ( Pan et al, 2012 ; Li et al, 2016 ; Chen et al, 2017 ), which found that C. brevicuspis cannot acclimatize to heavy sedimentation. In this experiment, we did not find the stimulatory effect of shallow burial on plant growth, which has been reported previously by other studies ( Pan et al, 2012 ; Chen et al, 2017 ). However, those studies were performed with single plants, and the stimulatory effect might be insignificant on larger population sizes.…”

“…Both shallow burial and smaller populations led to increased biomass allocation to aboveground parts. Under these conditions, plant growth might be limited by competition for soil nutrients ( Li et al, 2014 ; Chen et al, 2017 ); therefore, the high ratio of biomass allocation to aboveground parts can enable plants growing on the sediment surface to acquire the most limiting resources, such as light and oxygen ( Brown, 1997 ; Dech and Maun, 2006 ). However, biomass allocation to belowground parts was higher in deep burial treatments and large populations, indicating that competition for nutrient resources among clones is intense ( Brown, 1997 ; Maun, 1998 ; Deng et al, 2008 ).…”

“…Clonal plants, which are dominant in wetland ecosystems, can cope with complicated burial stresses by higher levels of phenotypic plasticity compared with non-clonal plants ( Dong et al, 1997 ; Santamaria, 2002 ; Li and Xie, 2009 ; Chen et al, 2011 ). In clonal plants, studies on the responses to sediment burial mostly focus on the plasticity of clonal architecture and the change in clonal growth forms, such as the length of rhizomes and the number of clumping or spreading ramets ( Klimes et al, 1993 ; Li and Xie, 2009 ; Chen et al, 2011 , 2017 ). However, clonal integration among interconnected ramets, generally aids clonal plants to endure frequently occurring sediment burial ( Yu et al, 2001 , 2004 ; Chen et al, 2010 ; Luo and Zhao, 2015 ).…”

Seagrasses benefit from mild anthropogenic nutrient additions

“…Examples of this are the debate between Cabaco et al (2013) and Vieira et al (2015), or inadequate analyses such as flawed PCA applications lacking criteria to screen the meaningful principal components and the variables significantly contributing to each of these components. Concomitantly, the efficiency of space occupation and its related phalanx and guerrilla clonal growth forms were used as indicators of the health of seagrass meadows (Sintes et al, 2005) as well as of meadows of other clonal plants in wetlands and their response to environmental stressors (Chen et al, 2011(Chen et al, , 2014(Chen et al, , 2017Geremew et al, 2018). Healthier meadows adopt the phalanx strategy by simultaneously growing new shoots and increasing their biomass.…”