Sardans J., Peñuelas J., Coll M., Vayreda J., Rivas-Ubach A. (2012) Stoichiometry of potassium is largely determined by water availability and growth in Catalonian forests. Functional Ecology. 26: 1077-1089.EnlaceDoi: 10.1111/j.1365-2435.2012.02023.x
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:C L/W, K:N L/W and K:P L/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:C L/W and K:N L/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. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
Doblas-Miranda E., Martinez-Vilalta J., Lloret F., Alvarez A., Avila A., Bonet F.J., Brotons L., Castro J., Curiel Yuste J., Diaz M., Ferrandis P., Garcia-Hurtado E., Iriondo J.M., Keenan T.F., Latron J., Llusia J., Loepfe L., Mayol M., More G., Moya D., Penuelas J., Pons X., Poyatos R., Sardans J., Sus O., Vallejo V.R., Vayreda J., Retana J. (0) Reassessing global change research priorities in mediterranean terrestrial ecosystems: How far have we come and where do we go from here?. Global Ecology and Biogeography. 24: 25-43.EnlaceDoi: 10.1111/geb.12224
Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. Location: Mediterranean terrestrial ecosystems. Methods: This article revisits the research priorities proposed in a 1998 assessment. Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. Main conclusions: (1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.
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