Tall Wheatgrass (Thinopyrum ponticum): Flood Resilience, Growth Response to Sea Water Immersion, and Its Capacity for Erosion and Flooding Control of Coastal Areas

Abstract

Integrated coastal zone management proposes nature-based mitigation strategies based on the replacement of artificial coastal stabilization and protection structures with dunes stabilized with plant species. These psammophytes stabilize sands and act as supporters, increasing dunes’ ability to reduce storm damages and effectively minimize erosion with minimal negative impacts to natural ecosystems. That is why searching for native salt-tolerant plants with extensive root systems and studying their capacity for erosion and flooding control is fundamental to the practice of ecologically-sound ecosystem services. The aim of the present study is to define the effects of flooding stress on a number of wheatgrass (Thinopyrum ponticum) plant life aspects (survival ability, viability, and growth response) in order to determine wheatgrass’s capacity as dune stabilizer. Conducted experiments established that T. ponticum was very tolerant to immersion impact and salt and oxygen deficiency stress, and its rhizomes were able to regenerate after 30 days in seawater. The temporal expression of its survival is presented as critical decomposition time (CDT) by linking the maximum duration of floods along the Bulgarian Black Sea Coast and the resilience of tall wheatgrass in flooding simulations. A statistical analysis of the experimental data demonstrated that immersion in sea water increases rhizome viability, biomass, and allocation to root biomass, whereas other factors, such as the duration of immersion, salinity, and temperatures of sea water have no significant effect. According to flood resilience and growth response to sea water submergence, T. ponticum demonstrated high potential to be a dune stabilizer.

Vulnerability assessment of coastal plant communities from flooding caused by unusual storms: A case study of Kabakum beach, Varna (Northeastern Bulgaria) for 2018 year

“…The proposed model was based on the experimental methods of simulating sea water floods without taking into consideration the direct mechanical effects of storm waves. Previous studies [3,7,9] demonstrated that experimental methods of direct submergence were more appropriate than the experiments of studying substrate salinity and salt spray due to regular exposure of dune plants to sea water and specific mechanisms of neutralizing sea water salt [3].…”

“…After a month of acclimatization in the Biological Laboratory of the Technical University of Varna, the plants with pots, separated in three equal groups, were completely submerged in three 100 l glass tanks full of sea water (18‰ salinity) with maintained constant temperatures of 4±1, 13±1, and 23±1 °C, respectively, for 480 hours. The water was changed twice a day in order to avoid water putrefactive processes [3,6,9].…”

“…The temporal expression of plant species survival can be presented as a critical decomposition time (CDT) by linking the duration of flooding and resilience of plant species. CDT is a parameter that is subjectively defined on visible morphological changes and represents the smallest degree of irreversible decay of vegetative organs (more than 15% of the whole vegetative organ surface), and it indicates that the plants will not survive flooding with longer duration and their communities will not be able to recover [3,6,7,12].…”

“…Coastal areas are very fragile ecosystems that are sensitive to global climate changes, sea level rise and frequent storm surges [1][2][3]. These areas, with their naturally established coastal dunes, perform important ecosystem services such as protection against storm waves, storm surges, and high tides [3,4], and act as a buffer for low-lying inland urbanized and agricultural territories [5,6]. They provide habitats for many rare and endangered species, which will be lost due to the combination of negative consequences of flooding and erosion as well as strengthen anthropogenic impact [3,6,7].…”

“…The only risk comes from extreme meteorological events such as unusual storm surge levels in combination with reinforced wave upon the shore [7,10,11]. Recorded damages from storms over the Bulgarian Black Sea Coast [7,8,9] showed the negative impact to the dunes and the high potential of the root systems of some of the native psammophytes to accumulate sand and prevent from washout [3,[9][10][11].…”