Camino-Serrano M., Guenet B., Luyssaert S., Ciais P., Bastrikov V., De Vos B., Gielen B., Gleixner G., Jornet-Puig A., Kaiser K., Kothawala D., Lauerwald R., Peñuelas J., Schrumpf M., Vicca S., Vuichard N., Walmsley D., Janssens I.A. (2018) ORCHIDEE-SOM: Modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe. Geoscientific Model Development. 11: 937-957.LinkDoi: 10.5194/gmd-11-937-2018
Current land surface models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, and thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. This common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to 2gm. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on and desorption from soil minerals, diffusion of SOC and DOC, and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: A coniferous forest, a deciduous forest, a grassland, and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- A nd depth-dependent parameterization of the new input model parameters, such as the turnover times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global warming. © Author(s) 2018.
Canelo T., GaytÁn Á., GonzÁlez-Bornay G., Bonal R. (2018) Seed loss before seed predation: experimental evidence of the negative effects of leaf feeding insects on acorn production. Integrative Zoology. 13: 238-250.LinkDoi: 10.1111/1749-4877.12292
Insect herbivory decreases plant fitness by constraining plant growth, survival and reproductive output. Most studies on the effects of herbivory in trees rely on correlational inter-individual comparisons and could, thus, be affected by confounding factors linked to both herbivory and plant performance. Using the Mediterranean Holm oak (Quercus ilex) as a study model, we followed an experimental approach in which leaf-feeding insects (mainly Lepidoptera caterpillars) were excluded from some shoots in all study trees. Shoots subjected to herbivore exclusion exhibited lower defoliation rates and produced more acorns than control shoots. Defoliation constrained shoot growth throughout the study period, but had no effect on the number of female flowers produced per shoot. Acorn production was, however, lower in control shoots due to their higher abortion rates, and also to their greater mortality risk during summer drought, as shoots with fewer leaves were less likely to survive. Plant reaction to herbivory inhibits certain physiological pathways involved in plant growth, which, together with the effects of physical damage, reduces the amount and efficiency of the photosynthetic tissue. This increases their vulnerability to environmental stresses, such as water deficit, which limit resource assimilation. Defoliation is likely a key factor affecting oak regeneration, as it may be a significant source of seed loss prior to pre-dispersal acorn predation. Further experimental studies could help to elucidate its effects in contrasting environments. In Mediterranean regions, the harsher droughts predicted by climate change models could worsen the effects of insect herbivory on oak reproductive output. © 2017 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd
Carabassa V., Ortiz O., Alcañiz J.M. (2018) Sewage sludge as an organic amendment for quarry restoration: Effects on soil and vegetation. Land Degradation and Development. 29: 2568-2574.LinkDoi: 10.1002/ldr.3071
Quarry restoration in Mediterranean environments usually needs organic amendments to improve the substrates used for technosol construction. Digested sewage sludges from municipal wastewater treatment plants are rich in organic matter, N, and P and constitute an available and economically interesting alternative for substrate amendment. However, their pollutant burden and labile organic matter content involve an environmental risk that must be controlled. Moreover, ecological succession in restored areas can be influenced by the use of sludge and should be assessed. To minimize these risks, a new sewage sludge dose criterion relating to its labile organic matter and heavy metal content has been established. Sewage sludge doses currently range between 10 and 50 Mg ha−1. In order to verify the suitability of this dose criterion, 16 areas rehabilitated using sewage sludge located in limestone quarries in a Mediterranean climate in Catalonia (NE Spain) have been assessed. These evaluations focused on physicochemical properties of rehabilitated soils, land degradation processes, and ecological succession. In the short term, 6 months after sludge application, an increment of organic matter content in the restored soils was observed, without significant increases in electrical conductivity or heavy metals content, and with a dense plant cover that contributes to effective soil erosion control. Two years after, ruderal plants were still present but later successional species colonized the restored zones in different degrees. These results suggest that sewage sludge, used as a soil amendment according to the proposed methodology, can safely improve technosol quality without constraints that compromise ecological succession. © 2018 John Wiley & Sons, Ltd.
Castellanos A.E., Llano-Sotelo J.M., Machado-Encinas L.I., López-Piña J.E., Romo-Leon J.R., Sardans J., Peñuelas J. (2018) Foliar C, N, and P stoichiometry characterize successful plant ecological strategies in the Sonoran Desert. Plant Ecology. 219: 775-788.LinkDoi: 10.1007/s11258-018-0833-3
Ecological processes are centered to water availability in drylands; however, less known nutrient stoichiometry can help explain much of their structure and ecological interactions. Here we look to the foliar stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) of 38 dominant plant species from the Sonoran Desert, grouped in four different functional types to describe ecological characteristics and processes. We found that foliar N, C:N, C:P, and N:P stoichiometric ratios, but not P, were higher than those known to most other ecosystems and indicate P but not N limitations in leaves. Biological N fixers (BNF) had even higher leaf N concentrations, but bio-elemental concentrations and stoichiometry ratios were not different to other non-N-fixing legume species which underscores the need to understand the physiological mechanisms for high N, and to how costly BNF can succeed in P-limiting drylands environments. Stoichiometry ratios, and to lesser extent elemental concentrations, were able to characterize BNF and colonizing strategies in the Sonoran Desert, as well as explain leaf attribute differences, ecological processes, and biogeochemical niches in this dryland ecosystem, even when no direct reference is made to other water-limitation strategies. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
Coll, L., Ameztegui, A., Collet, C., Löf, M., Mason, B., Pach, M., Verheyen, K., Abrudan, I., Barbati, A., Barreiro, S., Bielak, K., Bravo-Oviedo, A., Ferrari, B., Govedar, Z., Kulhavy, J., Lazdina, D., Metslaid, M., Mohren, F., Pereira, M., Peric, S., Rasztovits, E., Short, I., Spathelf, P., Sterba, H., Stojanovic, D., Valsta, L., Zlatanov, T., Ponette, Q. (2018) Knowledge gaps about mixed forests: What do European forest managers want to know and what answers can science provide?. Forest Ecology and Management. 407: 106-115.LinkDoi: 10.1016/j.foreco.2017.10.055
Connolly, J., Sebastià, M.-T., Kirwan, L., Finn, J.A., Llurba, R., Suter, M., Collins, R.P., Porqueddu, C., Helgadóttir, Á., Baadshaug, O.H., Bélanger, G., Black, A., Brophy, C., Čop, J., Dalmannsdóttir, S., Delgado, I., Elgersma, A., Fothergill, M., Frankow-Lindberg, B.E., Ghesquiere, A., Golinski, P., Grieu, P., Gustavsson, A.-M., Höglind, M., Huguenin-Elie, O., Jørgensen, M., Kadziuliene, Z., Lunnan, T., Nykanen-Kurki, P., Ribas, A., Taube, F., Thumm, U., De Vliegher, A., Lüscher, A. (2018) Weed suppression greatly increased by plant diversity in intensively managed grasslands: A continental-scale experiment. Journal of Applied Ecology. 55: 852-862.LinkDoi: 10.1111/1365-2664.12991
Courtois E.A., Stahl C., Van den Berge J., Bréchet L., Van Langenhove L., Richter A., Urbina I., Soong J.L., Peñuelas J., Janssens I.A. (2018) Correction to: Spatial Variation of Soil CO2, CH4 and N2O Fluxes Across Topographical Positions in Tropical Forests of the Guiana Shield (Ecosystems, (2018), (1-14), 10.1007/s10021-018-0232-6). Ecosystems. : 0-0.LinkDoi: 10.1007/s10021-018-0281-x
This paper was published with several formatting errors. It will be republished with corrections in place. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Courtois E.A., Stahl C., van Den Berge J., Bréchet L., van Langenhove L., Richter A., Urbina I., Soong J.L., Peñuelas J., Janssens I.A. (2018) Spatial Variation of Soil CO2, CH4 and N2O Fluxes Across Topographical Positions in Tropical Forests of the Guiana Shield. Ecosystems. : 1-14.LinkDoi: 10.1007/s10021-018-0232-6
The spatial variation of soil greenhouse gas fluxes (GHG; carbon dioxide—CO2, methane—CH4 and nitrous oxide—N2O) remains poorly understood in highly complex ecosystems such as tropical forests. We used 240 individual flux measurements of these three GHGs from different soil types, at three topographical positions and in two extreme hydric conditions in the tropical forests of the Guiana Shield (French Guiana, South America) to (1) test the effect of topographical positions on GHG fluxes and (2) identify the soil characteristics driving flux variation in these nutrient-poor tropical soils. Surprisingly, none of the three GHG flux rates differed with topographical position. CO2 effluxes covaried with soil pH, soil water content (SWC), available nitrogen and total phosphorus. The CH4 fluxes were best explained by variation in SWC, with soils acting as a sink under drier conditions and as a source under wetter conditions. Unexpectedly, our study areas were generally sinks for N2O and N2O fluxes were partly explained by total phosphorus and available nitrogen concentrations. This first study describing the spatial variation of soil fluxes of the three main GHGs measured simultaneously in forests of the Guiana Shield lays the foundation for specific studies of the processes underlying the observed patterns. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
Crowther T.W., Machmuller M.B., Carey J.C., Allison S.D., Blair J.M., Bridgham S.D., Burton A.J., Dijkstra F.A., Elberling B., Estiarte M., Larsen K.S., Laudon H., Lupascu M., Marhan S., Mohan J., Niu S., Peñuelas J.J., Schmidt I.K., Templer P.H., Kröel-Dulay G., Frey S., Bradford M.A. (2018) Erratum to: Crowther et al. reply (Nature, (2018), 554, 7693, (E7-E8), 10.1038/nature25746). Nature. 560: 0-0.LinkDoi: 10.1038/s41586-018-0192-1
In this Brief Communications Arising Reply, the affiliation for author P. H. Templer was incorrectly listed as ‘Department of Ecology & Evolutionary Biology, University of California Irvine, Irvine, California 92697, USA’ instead of ‘Department of Biology, Boston University, Boston, Massachusetts 02215, USA’. This has been corrected online. © 2018, Macmillan Publishers Ltd., part of Springer Nature.
Câmara T., Leal I.R., Blüthgen N., Oliveira F.M.P., Queiroz R.T., Arnan X. (2018) Effects of chronic anthropogenic disturbance and rainfall on the specialization of ant-plant mutualistic networks in the Caatinga, a Brazilian dry forest. Journal of Animal Ecology. : 0-0.LinkDoi: 10.1111/1365-2656.12820
Anthropogenic disturbance and climate change might negatively affect the ecosystem services provided by mutualistic networks. However, the effects of such forces remain poorly characterized. They may be especially important in dry forests, which (1) experience chronic anthropogenic disturbances (CADs) as human populations exploit forest resources, and (2) are predicted to face a 22% decline in rainfall under climate change. In this study, we investigated the separate and combined effects of CADs and rainfall levels on the specialization of mutualistic networks in the Caatinga, a seasonally dry tropical forest typical of north-eastern Brazil. More specifically, we examined interactions between plants bearing extrafloral nectaries (EFNs) and ants. We analysed whether differences in network specialization could arise from environmentally mediated variation in the species composition, namely via the replacement of specialist by generalist species. We characterized these ant-plant networks in 15 plots (20 × 20 m) that varied in CAD intensity and mean annual rainfall. We quantified CAD intensity by calculating three indices related to the main sources of disturbance in the Caatinga: livestock grazing (LG), wood extraction (WE) and miscellaneous resource use (MU). We determined the degree of ant-plant network specialization using four metrics: generality, vulnerability, interaction evenness and H2'. Our results indicate that CADs differentially influenced network specialization: we observed positive, negative, and neutral responses along LG, MU and WE gradients, respectively. The pattern was most pronounced with LG. Rainfall also shaped network specialization, markedly increasing it. While LG and rainfall were associated with changes in network species composition, this trend was not related to the degree of species specialization. This result suggests that shifts in network specialization might be related to changes in species behaviour, not species composition. Our study highlights the vulnerability of such dry forest ant-plant networks to climate change. Moreover, dry forests experience highly heterogeneous anthropogenic disturbances, creating a geographic mosaic of selective forces that may shape the co-evolution of interactions between ants and EFN-bearing plants. © 2018 British Ecological Society.
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