Stoichiometry of potassium is largely determined by water availability and growth in Catalonian forests

Abstract

Summary The study of the relationships between organisms and environmental elemental stoichiometry and ecosystem structure and function has recently received increasing attention. Some elements, however, have been less studied or have even been neglected. One of these elements is K, despite its critical importance in the water economy of plants. We hypothesized that K concentrations and especially K contents (concentrations × biomass), their stoichiometries with respect to C, N, and P contents, and their relative allocations to foliar and woody compartments would be linked to climatic gradients in the availability of water, forest type and growth. We tested this hypothesis by analysing the data set of the Catalan Forest Inventory. Evergreens, the type of tree with the slowest growth, showed the highest K contents, especially in wood, and the lowest plasticity to change the stoichiometry of K within and between foliar and woody biomasses along climatic gradients. The allocation of K to leaves in relation to the allocation of C, N and P increased with mean annual precipitation (MAP) and was concomitant with decreases in the allocation of K to wood in relation to the allocation of C, N and P (higher K:CL/W, K:NL/W and K:PL/W). In summer, the driest period, higher K:C, K:N and K:P content ratios in leaves were accompanied by lower K:C, K:N and K:P content ratios in wood, mainly in the species at the driest sites. Higher K:C and K:N content ratios in leaves and above‐ground biomass in all forest types, and higher K:CL/W and K:NL/W in conifers and deciduous trees were related to higher growth. K contents of leaves were better correlated with tree growth than were K concentrations of leaves in all forest types. These results show that the stoichiometry of K is strongly related to the availability of water and that the uptake of K is more related to the uptake of water than the uptake of N and P. Stoichiometric differences involving K are related to both the response of plants to drought and to plant growth. K thus plays a key role, together with N and P, in the response of plants to climatic gradients for improving the capacities for growth and adaptation to water stress along environmental gradients and through time (seasons). Moreover, these results show that the differences in stoichiometric composition and plasticity involving K contents can underlie the long‐term adaptation of trees to different ecological styles of life. K should thus be considered in ecological stoichiometric studies of terrestrial plants.

Potassium: a neglected nutrient in global change

“…Tomlinson et al (2013), while comparing leaf traits of different plant species growing in wet and arid environments, observed that leaves of species adapted to arid sites are small with high K concentrations. Furthermore, it was observed that tree species at the driest sites, such as in mediterranean evergreen and dry tropical forests, have a higher capacity to change their seasonal internal allocation of K, with a higher allocation of K to leaves during summer (the driest season) than the species at wetter sites (Milla et al, 2005;Rivas-Ubach et al, 2012;Sardans et al, 2012a).…”

“…Globally, however, plant K uptake appears to be associated with water availability (Sardans et al, 2011(Sardans et al, , 2012aGe et al, 2012), wherein a lower K uptake in turn negatively affects water uptake by reducing the activity of aquaporins (Kanai et al, 2011). All these interconnected relationships strongly suggest a cascade of higher water deficit, lower K uptake and a reduced capacity to avoid drought, which could become a serious problem in currently dry areas that are threatened by future drier scenarios.…”

Plant-soil interactions in Mediterranean forest and shrublands: impacts of climatic change

“…More retranslocation should thus lead to a low release of N and P from litter and lower availability of soil N and P. The high capacity for erosion of Mediterranean rain may have further favored the evolution of plants toward higher retranslocation to assure better control of nutrient stocks, thereby improving the capacity of the plant-soil system to retain nutrients. The high retranslocation is related to the observed higher percentage of nutrients in the stand biomass of Mediterranean forests compared with other forest types (Rodà et al 1999a, b;Sardans and Peñuelas 2012;Sardans et al 2012a).…”

Agricultural land use decouples soil nutrient cycles in a subtropical riparian wetland in China

“…These shifts are frequently associated to changes in the structure of plant communities and/or in nutrient outputs (e.g. crop harvesting and weathering) (Sardans et al, 2012a). Land-use changes due to agronomic practices and livestock production generate soil stoichiometric shifts in forests (Falkengren-Gerup et al, 2006;Sardans and Peñuelas, 2013), shrublands , grasslands (Mulder and Elser, 2009) and steppes (Jiao et al, 2013).…”