Drought and warming induced changes in P and K concentration and accumulation in plant biomass and soil in a Mediterranean shrubland

Sardans J., Peñuelas J., Prieto P., Estiarte M. (2008) Drought and warming induced changes in P and K concentration and accumulation in plant biomass and soil in a Mediterranean shrubland. Plant and Soil. 306: 261-271.
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Doi: 10.1007/s11104-008-9583-7

Resumen:

A field experiment involving drought and warming manipulation was conducted over a 6-year period in a Mediterranean shrubland to simulate the climate conditions projected by IPCC models for the coming decades (20% decreased soil moisture and 1°C warming). We investigated P and K concentration and accumulation in the leaves and stems of the dominant species, and in soil. Drought decreased P concentration in Globularia alypum leaves (21%) and in Erica multiflora stems (30%) and decreased K concentration in the leaves of both species (20% and 29%, respectively). The general decrease of P and K concentration in drought plots was due to the reduction of soil water content, soil and root phosphatase activity and photosynthetic capacity that decreased plant uptake capacity. Warming increased P concentration in Erica multiflora leaves (42%), but decreased it in the stems and leaf litter of Erica multiflora and the leaf litter (33%) of Globularia alypum, thereby demonstrating that warming improved the P retranslocation and allocation from stem to leaves. These results correlate with the increase in photosynthetic capacity and growth of these two dominant shrub species in warming plots. Drought and warming had no significant effects on biomass P accumulation in the period 1999-2005, but drought increased K accumulation in aboveground biomass (10 kg ha-1) in Globularia alypum due to the increase in K concentration in stems. The stoichiometric changes produced by the different responses of the nutrients led to changes in the P/K concentration ratio in Erica multiflora leaves, stems and litter, and in Globularia alypum stems and litter. This may have implications for the nutritional value of these plant species and plant-herbivore relationships. The effects of climate change on P and K concentrations and contents in Mediterranean ecosystems will differ depending on whether the main component of change is drought or warming. © 2008 Springer Science+Business Media B.V.

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Warming and drought alter C and N concentration, allocation and accumulation in a Mediterranean shrubland

Sardans J., Peñuuelas J., Estiarte M., Prieto P. (2008) Warming and drought alter C and N concentration, allocation and accumulation in a Mediterranean shrubland. Global Change Biology. 14: 2304-2316.
Enlace
Doi: 10.1111/j.1365-2486.2008.01656.x

Resumen:

We investigated the effects of warming and drought on C and N concentrations, nitrogen use efficiency (NUE), and C and N accumulation in different ecosystem compartments. We conducted a 6-year (1999-2005) field experiment to simulate the climate conditions projected by IPCC models for the coming decades in a Mediterranean shrubland. We studied the two dominant species, Globularia alypum and Erica multiflora, and an N-fixing species, Dorycnium pentaphyllum, also abundant in this shrubland. Warming (1°C) decreased N leaf concentrations by 25% and increased N stem concentrations by 40% in G. alypum. Although warming changed the available ammonium in soil in some seasons, it did not increase total soil N contents. Drought (19% average reduction in soil moisture) decreased leaf N concentrations in the two dominant shrub species, E. multiflora and G. alypum by 16% and 19%, respectively, and increased stem N concentrations by 56% and 40%, respectively. Neither warming nor drought changed the leaf N concentrations in the N-fixing species D. pentaphyllum, although warming increased stem N concentration by 9%. In G. alypum, the increase of stem N concentrations contributed to the observed increase of N accumulation in stem biomass in drought treatments with respect to control plots (8 kg Nha-1). Neither warming nor drought changed NUE in the period 1999-2005. Warming increased soil organic C relative to drought. The effects of warming and drought on C and N concentrations, on N accumulation and on leaf/stem N distribution were not the result of dilution or concentration effects produced by changes in biomass accumulation. Other factors such as the changes in soil N availability, photosynthetic capacity, and plant internal C and N remobilization must be involved. These changes which differed depending on the species and the plant tissue show that the climate change projected for the coming decades will have significant effects on the C and N cycle and stoichiometry, with probable implications for ecosystem structure and function, such as changes in plant-herbivore relationships, decomposition rates or community species composition. © 2008 The Authors Journal compilation © 2008 Blackwell Publishing.

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Transferencia de defenses de les plantes als herbívors.

Peñuelas J, Sardans J, Stefanescu C, Parella T, Filella I (2007) Transferencia de defenses de les plantes als herbívors. UAB DIVULGA 05/2007.

Drought changes phosphorus and potassium accumulation patterns in an evergreen Mediterranean forest

Sardans J., Peñuelas J. (2007) Drought changes phosphorus and potassium accumulation patterns in an evergreen Mediterranean forest. Functional Ecology. 21: 191-201.
Enlace
Doi: 10.1111/j.1365-2435.2007.01247.x

Resumen:

1. Climate models predict more extreme weather in Mediterranean ecosystems, with more frequent drought periods and torrential rainfall. These expected changes may affect major process in ecosystems such as mineral cycling. However, there is a lack of experimental data regarding the effects of prolonged drought on nutrient cycling and content in Mediterranean ecosystems. 2. A 6-year drought manipulation experiment was conducted in a Quercus ilex Mediterranean forest. The aim was to investigate the effects of drought conditions expected to occur over the coming decades, on the contents and concentrations of phosphorus (P) and potassium (K) in stand biomass, and P and K content and availability in soils. 3. Drought (an average reduction of 15% in soil moisture) increased P leaf concentration by 18.2% and reduced P wood and root concentrations (30.9% and 39.8%, respectively) in the dominant tree species Quercus ilex, suggesting a process of mobilization of P from wood towards leaves. The decrease in P wood concentrations in Quercus ilex, together with a decrease in forest biomass growth, led to an overall decrease (by approximately one-third) of the total P content in above-ground biomass. In control plots, the total P content in the above-ground biomass increased 54 kg ha-1 from 1999 to 2005, whereas in drought plots there was no increase in P levels in above-ground biomass. Drought had no effects on either K above-ground contents or concentrations. 4. Drought increased total soil soluble P by increasing soil soluble organic P, which is the soil soluble P not directly available to plant capture. Drought reduced the ratio of soil soluble inorganic P : soil soluble organic P by 50% showing a decrease of inorganic P release from P bound to organic matter. Drought increased by 10% the total K content in the soil, but reduced the soil soluble K by 20.4%. 5. Drought led to diminished plant uptake of mineral nutrients and to greater recalcitrance of minerals in soil. This will lead to a reduction in P and K in the ecosystem, due to losses in P and K through leaching and erosion, if the heavy rainfalls predicted by IPCC (Intergovernmental Panel on Climate Change) models occur. As P is currently a limiting factor in many Mediterranean terrestrial ecosystems, and given that P and K are necessary for high water-use efficiency and stomata control, the negative effects of drought on P and K content in the ecosystem may well have additional indirect negative effects on plant fitness. © 2007 The Authors.

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Drought changes the dynamics of trace element accumulation in a Mediterranean Quercus ilex forest

Sardans J., Peñuelas J. (2007) Drought changes the dynamics of trace element accumulation in a Mediterranean Quercus ilex forest. Environmental Pollution. 147: 567-583.
Enlace
Doi: 10.1016/j.envpol.2006.10.008

Resumen:

We conducted a field drought manipulation experiment in an evergreen oak Mediterranean forest from 1999 to 2005 to investigate the effects of the increased drought predicted for the next decades on the accumulation of trace elements that can be toxic for animals, in stand biomass, litter and soil. Drought increased concentrations of As, Cd, Ni, Pb and Cr in roots of the dominant tree species, Quercus ilex, and leaf Cd concentrations in Arbutus unedo and of Phillyrea latifolia codominant shrubs. The increased concentration of As and Cd can aggravate the toxic capacity of those two elements, which are already next or within the levels that have been shown to be toxic for herbivores. The study also showed a great reduction in Pb biomass content (100-135 g ha-1) during the studied period (1999-2005) showing the effectiveness of the law that prohibited leaded fuel after 2001. The results also indicate that drought increases the exportation of some trace elements to continental waters. © 2006 Elsevier Ltd. All rights reserved.

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Seasonal patterns of root-surface phosphatase activities in a Mediterranean shrubland. Responses to experimental warming and drought

Sardans J., Peñuelas J., Estiarte M. (2007) Seasonal patterns of root-surface phosphatase activities in a Mediterranean shrubland. Responses to experimental warming and drought. Biology and Fertility of Soils. 43: 779-786.
Enlace
Doi: 10.1007/s00374-007-0166-1

Resumen:

Mediterranean ecosystems are water limited and the current general circulation Models (GCM) and ecophysiological models forecast a warming and a further increase of drought in the next decades. A stronger water stress can decrease the capacity for nutrient absorption by plants. We conducted a field experiment to simulate forecasted drought and warming in a Mediterranean calcareous shrubland to assess the performance of root-surface phosphatase activities of the dominant shrub Globularia alypum. These enzyme activities were higher in autumn and spring, when the climate conditions were optimal for plant activity, than in summer or winter, when there was either lack of water or cold temperatures. A decrease in soil moisture in drought plots decreased root-surface phosphatase activity (29% in summer and 25% in autumn). The decrease in root-surface phosphatase activity in drought plots coincided with a decrease in P leaf concentrations and P accumulation in aboveground biomass and loss of photosynthetic capacity of some dominant shrub species of this ecosystem, and with a tendency to increase total soil-P. These results suggest that the expected drier conditions in this Mediterranean shrubland in the next decades will slow down the P uptake by plants, thereby, diminishing the P contents in biomass and increasing total P contents in soil in non-available forms and that this can be, in part, attributable to a result of the decrease in root-surface phosphatase activity. © 2007 Springer-Verlag.

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Females of the specialist butterfly Euphydryas aurinia (Lepidoptera: Nymphalinae: Melitaeini) select the greenest leaves of Lonicera implexa (Caprifoliaceae) for oviposition.

Stefanescu C, Peñuelas J, Sardans J, Filellla I (2006) Females of the specialist butterfly Euphydryas aurinia (Lepidoptera: Nymphalinae: Melitaeini) select the greenest leaves of Lonicera implexa (Caprifoliaceae) for oviposition. European Journal of Entomology 103: 569-574

Lonicera implexa leaves bearing naturally laid eggs of the specialist herbivore Euphydryas aurinia have dramatically greater concentrations of iridoid glycosides than other leaves

Peñuelas J., Sardans J., Stefanescu C., Parella T., Filella I. (2006) Lonicera implexa leaves bearing naturally laid eggs of the specialist herbivore Euphydryas aurinia have dramatically greater concentrations of iridoid glycosides than other leaves. Journal of Chemical Ecology. 32: 1925-1933.
Enlace
Doi: 10.1007/s10886-006-9118-8

Resumen:

We tested in the field the hypothesis that the specialist butterfly Euphydryas aurinia (Lepidoptera: Nymphalidae, Melitaeinae) lays eggs on leaves of Lonicera implexa (Caprifoliaceae) plants with greater iridoid concentrations. We conducted our investigations in a Mediterranean site by analyzing leaves with and without naturally laid egg clusters. There were no significant differences in iridoid glycoside concentrations between leaves from plants that did not receive eggs and the unused leaves from plants receiving eggs, a fact that would seem to indicate that E. aurinia butterflies do not choose plants for oviposition by their iridoid content. However, the leaves of L. implexa that bore egg clusters had dramatically greater (over 15-fold) concentrations of iridoid glycosides than the directly opposite leaves on the same plant. These huge foliar concentrations of iridoids (15% leaf dry weight) may provide specialist herbivores with compounds that they either sequester for their own defense or use as a means of avoiding competition for food from generalist herbivores. Nevertheless, it may still be possible that these high concentrations are detrimental to the herbivore, even if the herbivore is a specialist feeder on the plant. © Springer Science + Business Media, Inc. 2006.

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Introduction of the factor of partitioning in the lithogenic enrichment factors of trace element bioaccumulation in plant tissues

Sardans J., Peñuelas J. (2006) Introduction of the factor of partitioning in the lithogenic enrichment factors of trace element bioaccumulation in plant tissues. Environmental Monitoring and Assessment. 115: 473-498.
Enlace
Doi: 10.1007/s10661-006-7241-1

Resumen:

Bioindicators are widely used in the study of trace elements inputs into the environment and great efforts have been conducted to separate atmospheric from soil borne inputs on biomass accumulation. Many monitoring studies of trace element pollution take into account the dust particles located in the plant surface plus the contents of the plant tissues. However, it is usually only the trace element content in the plant tissues that is relevant on plant health. Enrichment factor equations take into account the trace element enrichment of biomasses with respect soil or bedrocks by comparing the ratios of the trace element in question to a lithogenic element, usually Al. However, the enrichment equations currently in use are inadequate because they do not take into account the fact that Al (or whichever reference element) and the element in question may have different solubility-absorption-retention levels depending on the rock and soil types involved. This constrain will become critical when results from different sites are compared and so in this article we propose that the solubility factors of each element are taken into account in order to overcome this constrain. We analysed Sb, Co, Ni, Cr, Pb, Cd, Mn, V, Zn, Cu, As, Hg, and Al concentration in different zones of Catalonia (NE Spain) using the evergreen oak Quercus ilex and the moss Hypnum cupressiforme as target species. We compared the results obtained in rural and non industrial areas with those from the Barcelona Metropolitan Area. We observed differences in Al concentrations of soils and bedrocks at each different site, together with the differences in solubility between Al and the element in question, and a weak correlation between total soil content and water extract content through different sites for most trace elements. All these findings show the unsuitability of the current enrichment factors for calculating lithospheric and atmospheric contributions to trace element concentrations in biomass tissues. The trace element enrichment factors were calculated by subtracting the part predicted by substrate composition (deduced from water extracts from soils and bedrock) from total concentrations. Results showed that for most of the trace elements analysed, trace elements enrichment factors were higher inside the Barcelona Metropolitan Area than outside, a finding that indicates that greater atmospheric inputs occur in urban areas. The results show that the most useful and correct way of establishing a reference for lithospheric and atmospheric inputs into the plant tissues is, first, to analyse samples of the same plant species collected from a number of sites possessing similar environmental conditions (climate, vegetation type, soil type) and, second, to use this new enrichment factor obtained by subtracting from the total concentration in plant tissue the predicted contribution of soil or bedrock extracts instead of that of total soil or bedrock concentrations. © Springer Science+Business Media, Inc. 2006.

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Warming and drought alter soil phosphatase activity and soil P availability in a Mediterranean shrubland

Sardans J., Peñuelas J., Estiarte M. (2006) Warming and drought alter soil phosphatase activity and soil P availability in a Mediterranean shrubland. Plant and Soil. 289: 227-238.
Enlace
Doi: 10.1007/s11104-006-9131-2

Resumen:

We conducted a field experiment simulating the warming and drought in a Mediterranean shrubland dominated by Erica multiflora and Globularia alypum with the aim to simulate the next future climate conditions predicted by the IPCC and ecophysiological models. As P is frequently a limiting nutrient in Mediterranean ecosystems, we investigated the drought and warming effects on soil phosphatases activities, soil P contents and availability, litter and leaf P concentration, and the capacity of this community to maintain soil P reserves and retain this nutrient in the ecosystem. Warming treatment increased soil and air temperature (an average of 1°C) and drought treatment decreased soil water content in one of the seasons analysed (28% in autum 2004). Warming increased (68%) the activities of soil acid phosphatases in summer and alkaline phosphatase activity (22%) in spring 2004, and increased P concentrations in E. multiflora. Instead, warming decreased P concentrations in litterfall of this same species, E. multiflora, and soil HCO3-extractable Pi (Olsen-Pi) in some seasons, decreasing total P soil concentration (37%) after 6 years of treatment. The drought treatment did not change soil phosphatase activities, nor available Pi. The effects of climate change on soil P dynamics in Mediterranean areas will thus be strongly dependent on whether the main variable involved in the local change is warming or drought. If warming is the main change without significant changes in water availability, the increases of biological activity can accelerate plant growth, P capture by plants and increase soil-phosphatase activity, altogether decreasing P contents in soil. If drought is the main change, a reduction in P demands by plants is expected, increasing P stocks in soils. © 2006 Springer Science+Business Media B.V.

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