Effects of farming practice on populations of threatened amphibious plant species in temporarily flooded arable fields: implications for conservation management

• The effects of farming practices on amphibious plant population dynamics were examined.
• Soiltillage had a positive effect on plant emergence, but reduced seed densities.
• Herbicideapplication negatively affected the establishment of all study species.
• Fertilisationaffected plant densities of Limosella aquatica.
• Reduced management intensity can help maintaining rare amphibious plant populations.

Intensification of land use has led to a severe decline of arable plants in the past decades, particularly among species of marginal habitats, such as temporarily flooded fields. Few studies have focused on the factors controlling the population dynamics of these species, and on suitable strategies for more effective conservation. To investigate the effects of farming practice on plant populations of temporarily flooded fields, we determined above-ground and below-ground densities of four annuals (Elatine alsinastrum, Limosella aquatica, Myosurus minimus and Peplis portula) in a 3-year on-farm experiment. A fully-factorial experiment combined the treatments soil tillage, presence of crops, fertilisation and herbicide application. Soil tillage had a positive effect on plant establishment, whereas herbicide application had a negative effect on the establishment of all study species. Plant densities were controlled by application of fertilisers and herbicides, with the most significant effects on L. aquatica and M. minimus. Soil seed densities were mainly affected by environmental factors, but tillage also significantly reduced the seed densities of E. alsinastrum and P. portula. Other farming practices had a minor impact. Thus, reduced management can help in maintaining populations of rare amphibious plant species. The effect of different crops, crop rotation and the timing of management will help in developing the most appropriate management strategies for conservation of these plant species.