Nitrogen and phosphorus allocation strategy among dominant species' major organs in desert grassland

Allometric allocation of limiting nutrient elements at the organ level is a crucial strategy for plants to adapt to environmental changes. However, our understanding of intra- and inter-organ allocation patterns of nitrogen ( N ) and phosphorus ( P ) in desert grassland plants remains limited. A one-year pot experiment (June 2020 to August 2021) was conducted to investigate the N - P allometric scaling relationships within and between plant organs of dominant shrubs and herbaceous species cultivated in two soil types: desert eolian sand soil (DESS) and brown calcic soil (BCS). The results indicated that, overall, the leaves of both shrubs and herbaceous plants exhibited higher N and P contents compared to other plant organs. Notably, under BCS conditions, fine roots of Ammopiptanthus mongolicus exhibited higher P content than leaves. For shrubs, N content in leaves changes faster than P content, while in other organs, P content increased faster than N content. The N - P allometric exponents for herbaceous leaves and roots were 0.47 and 0.56, respectively. Additionally, N and P contents in shrub leaves and fine roots were linearly positively correlated with soil total N and P contents. Generally, changes in soil type from DESS to BCS did not alter the N - P allometric scaling relationships within specific plant organs but did affect the N and P allocation in shrub fine roots. These findings enhance our understanding of N and P allocation strategies within and between major organs of desert plants. • N and P contents are closely coupled in plant organs. • leaf N and P contents were higher than those in other plant organs. • Soil type do not alter the N-P allometric allocation relationships. • Fine roots, being functional roots, exhibit high elemental plasticity.