Ecosystems

It’s not too late to save the carnivorous plants of Janggun wetland

Surveys of Janggun wetland in South Korea have found some parts have no carnivorous plants, but a study of the seed bank shows that they have the potential to return if the wetland is managed correctly.
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Janggun wetland, in southern Korea, is home to many plant species but is dominated by Molinia japonica, Japanese Moor Grass. In recent years, the grass has spread, and other species have disappeared. In a paper in September’s Ecological Engineering, Choi Yu Seong and Kim Jae Geun propose that changes in managing the wetland could allow these rare plants to return naturally.

Janggun wetland lies in the southeastern corner of Korea on Mount Geumjeong. Montane wetlands are relatively rare in Korea. The wetland is covered by grass, M. japonica which has a good trick for keeping other plants in check, and it can cover the ground to cast shade and prevent other plants from germinating. While M. japonica has seeds, it mainly reproduces vegetatively, so it isn’t a victim of its own success.

In the wetland in the past, there were also other rare plants. In particular, there were three carnivorous species Utricularia yakusimensisU. racemosa, and Drosera rotundifolia. However, these plants have suffered in recent hot weather, and since 2020, they have disappeared from Janggun wetland. In their paper, Choi and Kim wondered if ecologists could restore the plants missing from the wetland if their seeds could be persuaded to germinate.

Not surprisingly, for a wetland, the key ingredient is water. D. rotundifolia requires twelve weeks of wet and low temperatures before germinating in the warmth. U. yakusimensis, and U. racemosa need shallow water with few nutrients. In both cases, recent drought has broken these requirements and allowed the grasses to take hold of the area. This allowed M. japonica to secure its hold over the land by forming tussocks to shade out other seeds.

Drosera rotundifolia. Image: Canva.

Choi and Kim took samples of the soil in the wetland to examine the ‘seed bank’, the seeds waiting to germinate in the soil. They found that the seed bank was mainly seeds of annual plants. These are plants that go through their entire life cycle in one year and so have to grow from seed every year, but there were also seeds of perennial plants too. Among these seeds were the seeds of the carnivorous plants.

The findings suggest that if they had the opportunity, these seeds could germinate and allow the missing plants to return to their wetland. Choi and Kim then discuss how people could make this happen.

The authors propose two steps to restore the wetland. First, the plants will need the invasive grass removed, and then the drought problem needs to be tackled. They conclude, “The management (cutting and removing litter) of excessive expansion of M. japonica and maintenance of water level by the restoration of a small dam in the narrow middle part of Janggun wetland could enable the reemergence of these insectivorous plants that are in danger of disappearance in the wetland.”

READ THE ARTICLE

Choi, Y.S. and Kim, J.G. (2022) “Seed bank has potential for the restoration of insectivorous plants in Janggun montane wetland,” Ecological Engineering, 182(106728), https://doi.org/10.1016/j.ecoleng.2022.106728

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