Conservatism and plasticity of multiple nutrient allocation in wetland plants: Insights from allometric scaling

Abstract Nutrient utilization and allocation by plants is an important adaptive strategy in changing environments, thereby influencing primary production and biogeochemical cycling of ecosystems. Compared to macronutrients, the allocation strategies of micronutrients between plant organs and their differences from macronutrients remain understudied. Here, we explored whether consistent allocation patterns of multiple nutrients exist between leaves and roots of wetland plants, and whether these patterns are conservative or plastic across phylogeny, life forms and environmental gradients. We estimated the allocation strategies of multiple nutrients at individual, phylogeny and life form levels by analysing the scaling relationships of 16 elements (N, P, S, K, Ca, Mg, Na, Fe, Al, Mn, Si, B, Zn, Cu, Ni and Co) between leaves and roots of 54 plant species from 113 wetland sites across the arid and semi‐arid regions in northwestern China. We further tested how nutrient allocation strategies vary along temperature, nutrient and salinity gradients using bootstrapping methods. We found that the overall scaling exponents ( α ) between leaves versus roots varied greatly among 16 nutrient elements, ranging from 0.78 ( α S ) to 1.56 ( α Co ). Specifically, all elements except P showed allometric scaling relationships. The α N and α S were less than 1, indicating slower N and S accumulation in leaves than in roots, whereas the α values of the other 13 elements were greater than 1, indicating faster accumulation of these elements in leaves than in roots. The nutrient allocations were conserved across phylogeny and plant life forms. Nonetheless, water salinity, air temperature, soil and water nutrients altered the nutrient allocation between leaves and roots of wetland plants, with most nutrients accumulated faster in leaves than in roots with increasing salinity and temperature. The allocation of macronutrients between leaves and roots was jointly influenced by temperature, environmental nutrients and salinity, while the allocations of micronutrients were primarily driven by environmental nutrients. These findings demonstrate the existence of allometric nutrient allocation strategies among plant organs with different functions and the conservatism of such strategies across plant phylogeny and life forms. However, salinization, climate warming and nutrient heterogeneity may change nutrient allocation strategies of plants in wetlands under future global change. Read the free Plain Language Summary for this article on the Journal blog.