Control of runner reed (Phragmites japonicus) in lentic wetlands

Abstract

In lotic wetlands, runner reed (Phragmites japonicus) plays a role as a pioneer, which helps other plant species to settle by making dense roots trapping floating-sediments. In lentic wetlands, on the other hand, P. japonicus could play a role as an invader threatening biodiversity by forming tall and dense stands. To conserve an abandoned paddy terrace in mountainous areas, a habitat of an endangered dragonfly species (Nannophya pygmaea), from the monotypicoccupation by P. japonicus, we applied three kinds of treatment: (1) hand-clipping in 2009, (2) mechanical excavating in 2012, and (3) planting of alternative vegetational unit in 2012. We have monitored vegetation changes in the wetland in 2008~2012 and 2017. Vegetation cover of P. japonicus sharply decreased from 43% in 2011 to 16% in 2012 by the mechanical excavation. After 5 years from applying the treatment, Schoenoplectiella mucronata that was utilized in the planting became the predominant species instead of P. japonicus and the number of wetland plant species increased from 16 to 25 with the shift in species composition. This study showed the utility of three control methods of P. japonicas in a lentic wetland.

Changes in vegetation and flora of abandoned paddy terraces in responses to drawdown

“…Hydrological regimes including water depth (level), amplitude, and period are influential factors in determining the characteristics of wetland ecosystems (Carter 1986;Aldous et al 2005). In particular, water depth as a physical characteristic is known as a critical driver determining the vegetational components of wetland ecosystems (Nam et al 2014;Byun et al 2017;Hong et al 2018). On the other hand, decreases in water depth may alter the vegetational characteristics of wetland ecosystems and even cause terrestrialization (Lee et al 2002;Byun et al 2008), which means the transformation of wetlands into upland-like fields (Kirschner et al 2001).…”

“…On the other hand, it has also been reported that the introduction of tree species such as Salix spp. could be prevented in APTs when deep water condition is maintained (Hong and Kim 2013c;Choi and Kim 2015;Hong et al 2018).…”

“…ex Steud. and Lythrum anceps (Koehne) Makino exhibit high tolerance to dry stress, most wetland plant species are vulnerable to dry condition (Blossey et al 2001;Hong et al 2018). Thus, drawdown (draw-off) in wetland ecosystems, causing changes in hydrology, may alter wetland vegetation and flora as well (Odland and del Moral 2002).…”

“…Thus, many researchers have stressed the importance of management for stable hydrology in wetland ecosystems with considering the conservation of vulnerable species (Byun et al 2008;Hong and Kim 2016). Some researchers have noted that stable maintenances of water level in wetland ecosystems seems likely to be much important for some endangered species (Shin et al 2015;Hong et al 2018). Nevertheless, numerous studies have reported unintended changes in the vegetation and flora of wetland ecosystems particularly in responses to drawdown (ter Braak and Wiertz 1994;Odland and del Moral 2002).…”