Mass–density relationship changes along salinity gradient in Suaeda salsa L.

Whether and why the biomass–density (M–N) scaling relationship varies along environmental gradients were continuously debated in theoretical ecology. In this study, how soil salinity stress affects on the M–N scaling relationship was investigated by using Suaeda salsa L. in beach of Dongtai, Jiangsu Province, China. The results showed that the exponent of the scaling relationship (b) of low salinity level (−1.259) was smaller than that of middle salinity level (−1.025), which in turn was smaller than that high salinity level (−0.698). The plant height–crown radius (H–r) scaling exponents (∂) decreased with increasing salinity stress, while the canopy coverage–density (C–N) scaling exponents (β) showed an inverse trend. The predict data (b) based on ∂ and β by using the geometric model were statistically indistinguishable from their observed values for the three salinity levels. Moreover, two resources utilization parameters (l mean from root to leaf, a total area of leaves) of metabolic theory, photosynthetic rate, and water-use efficiency were more advantageous to Suaeda salsa L. of high stress than to those of low salinity. Therefore, it was implied that the changes of M–N relationship along salinity gradients may be resulted from their different geometric morphologies and resource utilization in response to salinity stress.