Transplanting macrophytes to rehabilitate streams: experience and recommendations

  • Published source details Riis T., Schultz R., Olsen H. & Katborg C.K. (2009) Transplanting macrophytes to rehabilitate streams: experience and recommendations. Aquatic Ecology, 43, 935-942.


Action: Transplant or replace blocks of vegetation

A replicated study in 2005–2006 in a degraded stream in Denmark (Riis et al. 2009) reported 25–79% survival of planted aquatic macrophyte beds over two growing seasons, and increases in the average size of some of the beds. Statistical significance was not assessed. Of the planted beds, 88–100% survived the first growing season and 25–79% survived the second growing season. Survival varied between species (water crowfoot Ranunculus baudotii x pseudofluitans vs water starwort Callitriche cophocarpa) and initial bed sizes (small vs large). Over the first growing season, the average size of survivors increased for all four bed types (from 0.12–0.24 m2 to 0.37–1.11 m2). The growth rate of individual beds was also positive (see original paper for data). During the second growing season, surviving crowfoot beds were larger than at the end of the first (1.42–1.80 m2) but surviving starwort beds were smaller (0.04–0.11 m2). Methods: In June 2005, forty-two aquatic macrophyte beds were created in a degraded, eroding, lowland stream (Lyngbygårds Å; 20–50 cm deep; 0.1–0.4 m/s flow). The beds were built by planting 0.06-m2 trays of vegetation and sediment that had been reared for six weeks in the stream. There were 4–19 beds for each combination of species and size. Bed survival was measured in September 2005 and September 2006. Bed area was measured in September 2005 and June 2006. Maximum growth rates were calculated from additional area measurements in June and August 2005.



Action: Transplant or replace blocks of vegetation

A before-and-after study in 2006–2008 in a stream in Denmark (Riis et al. 2009) reported 33–100% survival of trays of aquatic macrophytes over their first winter after planting, and quantified cover of the planted species after two years. Statistical significance was not assessed. Over the first winter, all trays survived for four of six planted species: water starwort Callitriche cophocarpa, Eurasian watermifoil Myriophyllum spicatum, curled pondweed Potamogeton crispus and water crowfoot Ranunculus baudotii x pseudofluitans. Trays of two other pondweed species had lower survival (33–50%). Two years after planting, all six species were present in the study reach. The most abundant species were curled pondweed (present on 44% of vegetated transects; 16% cover) and water crowfoot (present on 40% of vegetated transects; 14% cover). Before planting, the study reach contained no macrophytes. Methods: In June 2006, thirty-six 0.06-m2 trays of aquatic macrophytes were planted in a 1-km-long section of a recently created headwater stream (Voldbækken; 20–50 cm deep; 0.3–0.4 m/s flow). There were six trays for each of six species. Each tray was created using sediment and 45 plant shoots from the stream, then left to grow in the stream for six weeks before planting. Tray survival was measured in May 2007. Cover was recorded along 110 bank-to-bank transects in July 2008.

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