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

Abstract

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.