In agroecosystems, it is well known that nitrogen (N) can be transferred below-ground among plants, especially between legumes and forage crops. However, we still lack a deep mechanistic understanding of this ecological process and its implications in plant communities, especially in semi-arid environments where soil N availability depends on sporadic pulses of precipitation. This study comprehensively (i) assesses the prevalence of below-ground N transfer among the dominant species in a semi-arid scrubland community, (ii) examines the temporal dynamics and environmental influences on this transfer and (iii) assesses the impact of N transfer on the nutritional condition of the receiver plants (i.e. foliar N content). We quantified plant-plant 15N transfer between 126 pairs of plants through field experiments in which donors were 15N-labelled through foliar absorption, and the increment in foliar delta 15N of their neighbour plants (i.e. receiver) was periodically registered over two reproductive periods (14 months, 953 foliar samples). We selected pairs of plants of the nine most dominant species in the community (55 donors and 126 receivers). The donors were 15N-labelled at the beginning of the growing period (May) in the first reproduction period. Over the second, four more labelling pulses were applied. Below-ground N transfer was prevalent among all plant species. A 72% of the plants showed evidence of 15N transfer following the first pulse of 15N labelling. The magnitude of the transfer progressively increased across labelling pulses, with increments in foliar delta 15N values ranging from 0.82 parts per thousand to 12.35 parts per thousand. N transfer to receiver plants started in less than a week and reached the maximum delta 15N values approximately 60 days after labelling, getting back to pre-labelling values after 120 days. In donor plants, 15N enrichment lasted 170 days. Interestingly, multiple pulses of delta 15N showed an effect on the nutritional condition of the receiver, increasing its total foliar N content over a year. Plant-plant N transfer is a common ecological process taking place in this plant community and its effects on plant nutritional condition suggest that it can be a relevant mechanism shaping plant co-existence in N-poor environments.Read the free for this article on the Journal blog.