Fernández-Martínez M., Vicca S., Janssens I.A., Sardans J., Luyssaert S., Campioli M., Chapin F.S., Ciais P., Malhi Y., Obersteiner M., Papale D., Piao S.L., Reichstein M., Rodà F., Peñuelas J. (2015) Reply to 'Uncertain effects of nutrient availability on global forest carbon balance' and 'Data quality and the role of nutrients in forest carbon-use efficiency'. Nature Climate Change. 5: 960-961.LinkDoi: 10.1038/nclimate2794
[No abstract available]
Fernandez-Martinez M., Vicca S., Janssens I.A., Sardans J., Luyssaert S., Campioli M., Chapin Iii F.S., Ciais P., Malhi Y., Obersteiner M., Papale D., Piao S.L., Reichstein M., Roda F., Penuelas J. (2014) Nutrient availability as the key regulator of global forest carbon balance. Nature Climate Change. 4: 471-476.LinkDoi: 10.1038/nclimate2177
Forests strongly affect climate through the exchange of large amounts of atmospheric CO 2 (ref.). The main drivers of spatial variability in net ecosystem production (NEP) on a global scale are, however, poorly known. As increasing nutrient availability increases the production of biomass per unit of photosynthesis and reduces heterotrophic respiration in forests, we expected nutrients to determine carbon sequestration in forests. Our synthesis study of 92 forests in different climate zones revealed that nutrient availability indeed plays a crucial role in determining NEP and ecosystem carbon-use efficiency (CUEe; that is, the ratio of NEP to gross primary production (GPP)). Forests with high GPP exhibited high NEP only in nutrient-rich forests (CUEe = 33 ± 4%; mean ± s.e.m.). In nutrient-poor forests, a much larger proportion of GPP was released through ecosystem respiration, resulting in lower CUEe (6 ± 4%). Our finding that nutrient availability exerts a stronger control on NEP than on carbon input (GPP) conflicts with assumptions of nearly all global coupled carbon cycle-climate models, which assume that carbon inputs through photosynthesis drive biomass production and carbon sequestration. An improved global understanding of nutrient availability would therefore greatly improve carbon cycle modelling and should become a critical focus for future research. © 2014 Macmillan Publishers Limited.
Sardans J., Peñuelas J., Rodà F. (2006) Plasticity of leaf morphological traits, leaf nutrient content, and water capture in the Mediterranean evergreen oak Quercus ilex subsp. ballota in response to fertilization and changes in competitive conditions. Ecoscience. 13: 258-270.LinkDoi: 10.2980/i1195-6860-13-2-258.1
We manipulated nutrient availability and competing vegetation to investigate the phenotypic plasticity of leaf morphology and nutrient content of saplings and seedlings of the evergreen holm oak Quercus ilex subsp. ballota in response to nutrient pulses. Different factorial experimental designs were established with N and/or P pulse fertilization as factors in a field experiment in Catalonia (northeast Spain) and with P fertilization, soil type, and competitive situation as factors in a pot experiment. In the field, P fertilization decreased leaf mass per area (LMA) 9-13% in the 3 y following the fertilization application. No significant effect was observed from variations in N supply in any leaf cohort. In the pot experiment, P fertilization increased the leaf size, pre-dawn leaf water content, and root growth and decreased the LMA. P fertilization strongly increased P leaf concentrations, as in the field experiment. Neighbour competition induced increases in LMA in the second leaf cohort and in leaf density and size in both leaf cohorts; it also reduced root growth and tended to increase P leaf concentrations. Soil type had a significant effect on individual leaf area, leaf mass, and LMA, the latter being higher in siliceous soils than in calcareous and artificial soils. The pattern of change in leaf thickness across the different soil types was the opposite of that for leaf P concentrations, P contents per unit of leaf area, and leaf density. These results point to a morphological leaf plasticity in response to P availability, competitive situation, and soil type. The relations between the changes in leaf morphology, leaf nutrient content, root growth, and pre-dawn leaf water content changed depending on the factor that induced them. However, leaf morphological traits changed in combination with other plant traits such as root growth and nutrient contents in order to balance resource availability and production capacity under different environmental conditions, such as changing degrees of neighbour competition or water availability. This plasticity of sclerophyllous leaf traits in response to nutrient pulses makes Quercus ilex subsp. ballota well suited to adapt to the unpredictable changes and stress situations likely to result from current and immediate future climate and other changes in the Mediterranean region.
Sardans J., Peñuelas J., Rodà F. (2006) The effects of nutrient availability and removal of competing vegetation on resprouter capacity and nutrient accumulation in the shrub Erica multiflora. Acta Oecologica. 29: 221-232.LinkDoi: 10.1016/j.actao.2005.10.006
Nutrient availability is increasing in the Mediterranean Basin due to the great number and intensity of fires and higher levels of anthropomorphic pollution. In the experiment described in this paper, we aimed to determine the effects of N and P availability and of the removal of competing vegetation on resprouter capacity, biomass, and nutrient accumulation in Erica multiflora. Plants of the resprouter species E. multiflora were clipped to 0% of aerial biomass in a post-fire Mediterranean shrubland and fertilisation experiments and removal of competing vegetation were established in a factorial design. The resprouting of clipped plants was monitored during the first year after clipping and at the end of the year, all plant resprout populations were harvested and their resprout structure, biomass and N and P content measured. N fertilisation had no significant effect on leaf biomass either at plant level or on the total aerial biomass per stump unit area; however N concentration in resprout biomass did increased. P fertilisation slightly increased resprouting vigour and had a significant effect on P content of the leaf biomass. The removal of competing vegetation increased the ratio between leaf biomass and stem biomass, the lateral expansion of resprout, the hierarchy of resprouts branching, and the P content of stems, above all when P fertilisation was applied. These results show that as a response to decreased competition E. multiflora has the capacity to modify the relative proportions of the nutrients in the aerial biomass. All these characteristics allow E. multiflora to persist in increasingly disturbed Mediterranean ecosystems and contribute to the retention of nutrients in the ecosystem during early resprouting phases. © 2006 Elsevier SAS. All rights reserved.
Sardans J., Rodà F., Peñuelas J. (2006) Effects of a nutrient pulse supply on nutrient status of the Mediterranean trees Quercus ilex subsp. ballota and Pinus halepensis on different soils and under different competitive pressure. Trees - Structure and Function. 20: 619-632.LinkDoi: 10.1007/s00468-006-0077-z
Nutrient availability is a key factor in Mediterranean ecosystems that affects the primary productivity and the community structure. The great variability of its natural availability is now increasing due to frequent fires, pollution events and changes in rainfall regime associated to climate change. Quercus ilex ssp. ballota and Pinus halepensis are the most abundant tree species in the NW Mediterranean basin. They frequently compete in the early and middle successional stages. We investigated the effects of N and P pulse supplies on nutrient uptake capacity in these two species in an after-fire field area and in nursery conditions on different soil types and competing conditions. In the field, N fertilisation had weak effects on nutrient concentration and mineralomass likely as a consequence of this nutrient not being limiting in this field site whereas P fertilisation increased the P mineralomass and the Mg, S, Fe, K and Ca concentrations and mineralomass in the different biomass fractions of both species 1 and 3 years after fertilisation application. In the nursery experiments, P fertilisation increased the mineralomass and concentrations of P, Mg, S, Fe, K and Ca in all biomass fractions including the roots in both species and in different soils and competition conditions. The increment of nutrient mineralomass was due to both the increase of growth and of nutrient concentrations. Both species were able to absorb significant amounts of the P applied by fertilisation (between 5 and 20%) in short time (18 months). Competing vegetation decreased the positive effects of P fertilisation, and in many cases the negative effect of competing vegetation on nutrient mineralomass was stronger when P availability was increased by fertilisation. Q. ilex subsp ballota showed a greater competitive ability for P than the more pioneer species Pinus halepensis in the field but not in the nursery conditions. Pinus halepensis had greater nutrient mineralomass in calcareous than in siliceous soils. Q. ilex subsp. ballota had a higher root biomass allocation and root nutrient allocation than P. halepensis, but both species showed a high capacity to increase their nutrient uptake when its availability increased by fertilisation, thus assuring a great nutrient reserve for future growth periods and contributing to retain nutrients in the ecosystem. © Springer-Verlag 2006.
Sardans J., Peñuelas J., Rodà F. (2005) Changes in nutrient use efficiency, status and retranslocation in young post-fire regeneration Pinus halepensis in response to sudden N and P input, irrigation and removal of competing vegetation. Trees - Structure and Function. 19: 233-250.LinkDoi: 10.1007/s00468-004-0374-3
The capacity of Mediterranean species to adapt to variable nutrient supply levels in a global change context can be a key factor to predict their future capacity to compete and survive in this new scenario. We aimed to investigate the capacity of a typical Mediterranean tree species, Pinus halepensis, to respond to sudden changes in N and P supply in different environmental conditions. We conducted a fertilisation, irrigation and removal of competing vegetation experiment in a calcareous post-fire shrubland with an homogeneous young (5 years old) population of P. halepensis in order to investigate the retranslocation and nutrient status for the principal nutrients (N, P, Mg, K, S, Ca and Fe), and the nutrient use efficiency (NUE) of the most important nutrients linked to photosynthetic capacity (N, P, Mg and K). P fertilisation increased P concentration in needles, P, N, Mg and K retranslocations, and NUE calculated as biomass production per unit of nutrient lost in the litterfall. The P fertilisation was able to increase the aboveground biomasses and P concentration 3 years after P fertiliser application. Those responses to P fertilisation were enhanced by the removal of competing vegetation. The N needle and litterfall concentration decreased after P fertilisation and this effect was greater when the P fertilisation was accompanied by removal of competing vegetation. The increase of P availability decreased the P-NUE and increased the N-NUE when these variables were calculated as aboveground biomass production per unit of P present in the biomass. Both P-NUE and N-NUE increased when calculated as total aboveground production per unit of nutrient loss. The results show that it is necessary to calculate NUE on a different basis to have a wider understanding of nutrient use. The irrigation did not change the needle nutrient concentrations and the litterfall production, but it significantly changed the nutrient litterfall concentrations and total aboveground contents (especially P and K). These results show a high capacity of P. halepensis to quickly respond to a limiting nutrient such as P in the critical phases of post-fire regeneration. The increase in P availability had a positive effect on growth and P concentrations and contents in aboveground biomass, thus increasing the capacity of growth in future periods and avoiding immediate runoff losses and leachate. This capacity also strongly depends on neighbour competition. © Springer-Verlag 2005.
Sardans J., Rodà F., Peñuelas J. (2005) Effects of water and a nutrient pulse supply on Rosmarinus officinalis growth, nutrient content and flowering in the field. Environmental and Experimental Botany. 53: 1-11.LinkDoi: 10.1016/j.envexpbot.2004.02.007
Rosmarinus officinalis is a dominant shrub species of calcareous Mediterranean communities that has increased its presence in wide areas due to fire frequency increase and field abandonment. We aimed to study the capacity of adult shrubs to respond to nutrient pulses such as those produced by fires and human driven eutrophycation. In a 5 years old post-fire Mediterranean shrubland we conducted an experiment to investigate the effects of irrigation and N and P fertilisation on the growth, nutrient status and flowering effort of adult plants of the dominant shrub R. officinalis in a post-fire shrubland. The responses were monitored during the immediate 3 years after fertilisation. P fertilisation increased plant growth, produced a great increase in P aerial mineralomass and P concentration in leaf and stems and had a slight positive effect on flowering effort. Irrigation increased plant growth, but did not have significant effects on nutrient contents and flowering. The results show that adult individuals of the Mediterranean shrub R. officinalis have a notable capacity to positively respond in growth and in nutritional status to a sudden increase of the limiting nutrient, in this case P, and in a lesser extent, to an increase of water supply. These capacities may be important under the more unpredictable nutrient and water availability conditions expected for the near future; they will allow to take advantage of the pulses of higher nutrient and water availability in the middle of dry periods, thus increasing the community capacity to improve the nutrient retention in the ecosystem. © 2004 Elsevier B.V. All rights reserved.
Beier C., Emmett B., Gundersen P., Tietema A., Peñuelas J., Estiarte M., Gordon C., Gorissen A., Llorens L., Roda F., Williams D. (2004) Novel approaches to study climate change effects on terrestrial ecosystems in the field: Drought and passive nighttime warming. Ecosystems. 7: 583-597.LinkDoi: 10.1007/s10021-004-0178-8
This article describes new approaches for manipulation of temperature and water input in the field. Nighttime warming was created by reflection of infrared radiation. Automatically operated reflective curtains covered the vegetation at night to reduce heat loss to the atmosphere. This approach mimicked the way climate change, caused by increased cloudiness and increased greenhouse gas emissions, alters the heat balance of ecosystems. Drought conditions were created by automatically covering the vegetation with transparent curtains during rain events over a 2-5-month period. The experimental approach has been evaluated at four European sites across a climate gradient. All sites were dominated (more than 50%) by shrubs of the ericaceous family. Within each site, replicated 4-m X 5-m plots were established for control, warming, and drought treatments and the effect on climate variables recorded. Results over a two-year period indicate that the warming treatment was successful in achieving an increase of the minimum temperatures by 0.4-1.2°C in the air and soil. The drought treatment resulted in a soil moisture reduction of 33%-82% at the peak of the drought. The data presented demonstrate that the approach minimizes unintended artifacts with respect to water balance, moisture conditions, and light, while causing a small but significant reduction in wind speed by the curtains. Temperature measurements demonstrated that the edge effects associated with the treatments were small. Our method provides a valuable tool for investigating the effects of climate change in remote locations with minimal artifacts.
Sardans J, Rodà F, Peñuelas J (2004) Phosphorus limitation and competitive capacities of Pinus halepensis and Quercus ilex subsp. rotundifolia on different soils. Plant Ecology 174:305-317.
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