Characterization of the long‐distance dispersal of Johnsongrass (Sorghum halepense) in a vegetated irrigation channel

Abstract

Hydrochorous dispersal may play a major role in the propagation of weeds such as Sorghum halepense (Johnsongrass). However, the long-distance dispersal of this weed via agricultural intermittent channel networks, such as irrigation channels, has been poorly studied. In this study, we focused on a seed dispersal kernel obtained after an irrigation event in a vegetated channel. The main objectives of the study were to highlight the specificities of irrigation channels in relation to seed transport and investigate hydraulic factors and microscale channel features associated with the deposition of seeds along the channel. Our results showed that despite very different flow and morphological conditions compared with natural waterways, seeds of Johnsongrass were able to travel hundred meters at the scale of one irrigation event. This is likely due to the floating ability of more than 50% of the Johnsongrass seeds. A Regression Tree algorithm, which explained 72% of seed deposition variability, showed the importance of the channel features such as the width of the section and the hydraulic structures, sluice gates and culvert, to explain the patterns of seed deposition. A complex role of the emergent vegetation was highlighted. The results suggest that a threshold of vegetation density should be reached to enhance seed deposition. The results indicate that the spread of existing Johnsongrass populations could be limited by preserving existing hydraulic structures or maintaining areas where the density of terrestrial vegetation is sufficient to enhance seed retention downstream.

Multifunctionality of agricultural channel vegetation : A review based on community functional parameters and properties to support ecosystem function modeling

“…Vegetation also slows the transfer of pesticides to receiving ecosystems (Dollinger et al, 2015(Dollinger et al, , 2016Margoum et al, 2003;Lagacherie et al, 2006), and therefore favors their degradation in the channels. Last, standing vegetation influences the dispersal of species through agricultural channels by retaining plant propagules (seeds and other propagules such as rhizomes) transported by water (Rudi et al, 2018a;Soomers et al, 2010). This limits the spread of adventitious propagules in cultivated areas (Rudi et al, 2018a) but consequently also limits the dispersal of non-adventitious or protected species.…”

“…Last, standing vegetation influences the dispersal of species through agricultural channels by retaining plant propagules (seeds and other propagules such as rhizomes) transported by water (Rudi et al, 2018a;Soomers et al, 2010). This limits the spread of adventitious propagules in cultivated areas (Rudi et al, 2018a) but consequently also limits the dispersal of non-adventitious or protected species.…”

“…Due to the inherent difficulty of taking into account some plant parameters such as the specific architecture of plants at the scale of the community in heterogeneous plant covers,Rudi et al (2018a);Vinatier et al (2018) relied on a measure of the area of vegetation at the water surface (at the scale of a section of approximately one meter), accounting for the porosity of vegetation, because this property was assumed to explain seed deposition with good performance. These metrics were assessed through image analysis (Structure-from-Motion using Multi-View Stereo algorithm).…”

A novel platform to evaluate the dampening of water and solute transport in an experimental channel under unsteady flow conditions

“…Rare are the experiments that deal with solute transport in channels under well‐controlled conditions and unsteady state flow events. In the literature, some studies were carried on real‐scale channels (e.g., Errico et al, ; Newson, ; Rudi, Bailly, Belaud, & Vinatier, ) and on laboratory channels (Vinatier, Bailly, & Belaud, ) for various purposes according to project features: impact of land use change on floods (Jung, Kang, Hong, & Yeo, ), impact of dikes on inundation (Ettema & Muste, ), impact of vegetation on hydraulic resistance (Defina & Peruzzo, ; Errico et al, ), role of flow conditions in hydraulic properties (Rouzes, Moulin, Florens, & Eiff, ) and in biofilm colonization (Coundoul et al, ), and so on. The experiment size should verify hydraulic laws of similitude (Chanson, ).…”

“…These laboratories are generally used not only for fundamental research and teaching purposes but also for various applied research projects: river engineering and hydraulic model calibration (see a synthesis in Vidal, ), fluid measurement (Defina & Peruzzo, ; Vinatier et al, ), the hydrology of surface drainage and run‐off (Govers, Takken, Helming, ), flooding and its prevention (Ettema & Muste, ), sediment transport (Iverson, Logan, LaHusen, & Berti, ; Taccone, ), sizing of fish passes (Cassan & Laurens, ; Cassan, Tran, Courret, Laurens, & Dartus, ), river ecosystem management (Errico et al, ; Newson, ; Rudi et al, ), water supply and distribution, irrigation, hydropower, dams studies, and other applications. These experiments enable collecting data under real‐scale conditions and for fully controlled laboratory‐scale conditions where all the terms of water balance are measured.…”