Seasonal allocation of dry matter and nitrogen in Th. intermedium across stand ages

Abstract

Thinopyrum intermedium is currently proposed as a perennial grain for both forage and grain production. Undergoing domestication, its grain yields are low, while its long-lasting organs are ensuring environmental benefits. However, understanding the resource allocation dynamics of Th. intermedium is needed. Dry matter (DM) and nitrogen (N) allocations within the different plant parts were quantified over the growing season on various experimental sites and stand ages. Low resource mobilization to spikes was observed after flowering, contrarily to N allocation within stem bases. Indeed, root production and stem bases thickening over the years represented significant N sinks. In addition, the total N within the plant, weakly allocated to spikes (i.e., 10–26 %), can decrease at the end of the growing season (i.e., from 34 to 56 kg ha⁻¹). This could be explained by root turnover and release of N-rich root exudates to the soil. With a low exportation of N at grain maturity, averaging 60 kg ha⁻¹, a strategy of nutrient conservation was highlighted. Furthermore, through a small proportion of rhizomes, Th. intermedium is characterized by a conservative phalanx growth strategy. However, plant growth conditions could modulate rhizomes’ production as variation within varying stand densities were observed. Finally, we observed an increase of allocation to stem bases in older stands, coupled to a decrease of the reproductive allocation through lower proportion of reproductive tillers. Thus, work dedicated to understanding the allocation of resources in the plant will be beneficial to help identify possible synergies and trade-offs between grain production and ecological services.