Influence of watering with irrigation tubes on the nature reserve for Primula sieboldii E.Morren in the Tajimagahara flood plain. A three-year experiment.

Abstract

Shortage of soil water content is a major threat to wetland vegetation's decline. The effects of watering using irrigation tubes on plant communities were investigated in the Tajimagahara flood plain, Saitama Prefecture, where the nature-reserve population of a threatened species, Primula sieboldii E.Morren, has persisted. The watering system was established in 2022. Since then, the growth patterns of P. sieboldii and several major dominant species were compared for three years between plots with and without watering. P. sieboldii had longer leaves and higher stature in plots with than without watering, but only in 2022. Euphorbia adenochlora C.Morren et Decne. had higher cover and stature in plots with watering for three years. E. adenochlora performed better in earlier seasons in later years. These indicate that continued watering enhanced the steady growth of E. adenochlora with the year, which would, in turn, mask the better growth of P. sieboldii observed in 2022.