Carbon and nitrogen balances for six shrublands across Europe

Beier C., Emmett B.A., Tietema A., Schmidt I.K., Penũelas J., Láng E.K., Duce P., De Angelis P., Gorissen A., Estiarte M., De Dato G.D., Sowerby A., Kröel-Dulay G., Lellei-Kovács E., Kull O., Mand P., Petersen H., Gjelstrup P., Spano D. (2009) Carbon and nitrogen balances for six shrublands across Europe. Global Biogeochemical Cycles. 23: 0-0.
Enllaç
Doi: 10.1029/2008GB003381

Resum:

Shrublands constitute significant and important parts of European landscapes providing a large number of important ecosystem services. Biogeochemical cycles in these ecosystems have gained little attention relative to forests and grassland systems, but data on such cycles are required for developing and testing ecosystem models. As climate change progresses, the potential feedback from terrestrial ecosystems to the atmosphere through changes in carbon stocks, carbon sequestration, and general knowledge on biogeochemical cycles becomes increasingly important. Here we present carbon and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m-2 to 18,546 g C m-2, and the systems ranged from being net sinks (126 g C m -2 a-1) to being net sources (-536 g C m-2 a-1) of carbon with the largest storage and sink of carbon at wet and cold climatic conditions. The soil carbon store dominates the carbon budget at all sites and in particular at the site with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation was more than 5 times aboveground litterfall carbon which is significantly greater than the factor of 2 reported in a global analysis of forest data. Nitrogen storage was also dominated by the soil pools generally showing small losses except when atmospheric N input was high. The study shows that in the future a climate-driven land cover change between grasslands and shrublands in Europe will likely lead to increased ecosystem C where shrublands are promoted and less where grasses are promoted. However, it also emphasizes that if feedbacks on the global carbon cycle are to be predicted it is critically important to quantify and understand belowground carbon allocation and processes as well as soil carbon pools, particularly on wet organic soils, rather than plant functional change as the soil stores dominate the overall budget and fluxes of carbon. Copyright 2009 by the American Geophysical Union.

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A la recerca de les marmotes.

López BC, Subiranas J (2009) A la recerca de les marmotes. Cavall Fort 1131: 20-23.

Prediccions meteorològiques per preservar espècies vegetals.

López BC (2009) Prediccions meteorològiques per preservar espècies vegetals. UAB Divulga

L’edat de les oliveres monumentals i singulars del Montsià.

Martínez-Vilalta J, Claramunt B, Arnan X, Estorach M, Poyatos R (2009) L’edat de les oliveres monumentals i singulars del Montsià. Raïls 25: 208-221.

Drought, warming and soil fertilization effects on leaf volatile terpene concentrations in Pinus halepensis and Quercus ilex

Blanch J.-S., Peñuelas J., Sardans J., Llusià J. (2009) Drought, warming and soil fertilization effects on leaf volatile terpene concentrations in Pinus halepensis and Quercus ilex. Acta Physiologiae Plantarum. 31: 207-218.
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Doi: 10.1007/s11738-008-0221-z

Resum:

The changes in foliar concentrations of volatile terpenes in response to water stress, fertilization and temperature were analyzed in Pinus halepensis and Quercus ilex. The most abundant terpenes found in both species were α-pinene and Δ3-carene. β-Pinene and myrcene were also abundant in both species. P. halepensis concentrations were much greater than those of Q. ilex in agreement with the lack of storage in the latter species (15205.60 ± 1140.04 vs. 0.54 ± 0.08 μg g-1 [d.m.]). The drought treatment (reduction to 1/3 of full watering) significantly increased the total terpene concentrations in both species (54% in P. halepensis and 119% in Q. ilex). The fertilization treatment (addition of either 250 kg N ha-1 or 250 kg P ha-1 or both) had no significant effects on terpene foliar concentrations. The terpene concentrations increased from 0.25 μg g-1 [d.m.] at 30°C to 0.70 μg g-1 [d.m.] at 40°C in Q. ilex (the non-storing species) and from 2,240 μg g-1 [d.m.] at 30°C to 15,621 μg g-1 [d.m.] at 40°C in P. halepensis (the storing species). Both species presented negative relationship between terpene concentrations and relative water contents (RWC). The results of this study show that higher terpene concentrations can be expected in the warmer and drier conditions predicted for the next decades in the Mediterranean region. © 2008 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences.

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Plant-pollinator networks: Adding the pollinator's perspective

Bosch J., Martín González A.M., Rodrigo A., Navarro D. (2009) Plant-pollinator networks: Adding the pollinator's perspective. Ecology Letters. 12: 409-419.
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Doi: 10.1111/j.1461-0248.2009.01296.x

Resum:

Pollination network studies are based on pollinator surveys conducted on focal plants. This plant-centred approach provides insufficient information on flower visitation habits of rare pollinator species, which are the majority in pollinator communities. As a result, pollination networks contain very high proportions of pollinator species linked to a single plant species (extreme specialists), a pattern that contrasts with the widely accepted view that plant-pollinator interactions are mostly generalized. In this study of a Mediterranean scrubland community in NE Spain we supplement data from an intensive field survey with the analysis of pollen loads carried by pollinators. We observed 4265 contacts corresponding to 19 plant and 122 pollinator species. The addition of pollen data unveiled a very significant number of interactions, resulting in important network structural changes. Connectance increased 1.43-fold, mean plant connectivity went from 18.5 to 26.4, and mean pollinator connectivity from 2.9 to 4.1. Extreme specialist pollinator species decreased 0.6-fold, suggesting that ecological specialization is often overestimated in plant-pollinator networks. We expected a greater connectivity increase in rare species, and consequently a decrease in the level of asymmetric specialization. However, new links preferentially attached to already highly connected nodes and, as a result, both nestedness and centralization increased. The addition of pollen data revealed the existence of four clearly defined modules that were not apparent when only field survey data were used. Three of these modules had a strong phenological component. In comparison to other pollination webs, our network had a high proportion of connector links and species. That is, although significant, the four modules were far from isolated. © 2009 Blackwell Publishing LtdCNRS.

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Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling.

Keenan T, Garcia R, Friend AD, Zaehle S, Gracia C, Sabate S (2009) Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling. Biogeosciences 6: 1423-1444.

Ant community structure in citrus orchards in the mediterranean basin: Impoverishment as a consequence of habitat homogeneity

Cerdá X., Palacios R., Retana J. (2009) Ant community structure in citrus orchards in the mediterranean basin: Impoverishment as a consequence of habitat homogeneity. Environmental Entomology. 38: 317-324.
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Doi: 10.1603/022.038.0203

Resum:

This study analyzes the structure and composition of ant communities in citrus orchards in Catalonia (northeast Spain) and compares them with the ant fauna found in natural communities of the region. In the citrus orchards considered in this study, the most abundant species were Lasius niger and Pheidole pallidula, which are behaviorally dominant species. Two other dominant species, Linepithema humile and Tetramorium caespitum, were also abundant, although only in one orchard. Species richness and diversity in the studied orchards were low compared with natural communities: although in orchards, there were few species and low diversity values, in natural communities, the number of species was higher and diversity also increased. This reduction of species richness and diversity was not modified by edge effects: only light and local differences were found between the inner part of the orchards and the orchard margins, and differences among orchards were greater than differences between inner parts and edges. The activity peaks of the different ant species actively foraging on these citrus orchards were distributed throughout the whole activity period of ants. Overall, the composition of ant communities present in the citrus orchards of this study was extremely poor. This agrees with the fact that monocultures are ecosystems associated with an inevitable loss of biodiversity and abundance of insect populations. © 2009 Entomological Society of America.

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European map of alien plant invasions based on the quantitative assessment across habitats

Chytrý M., Pyšek P., Wild J., Pino J., Maskell L.C., Vilà M. (2009) European map of alien plant invasions based on the quantitative assessment across habitats. Diversity and Distributions. 15: 98-107.
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Doi: 10.1111/j.1472-4642.2008.00515.x

Resum:

Aim: Recent studies using vegetation plots have demonstrated that habitat type is a good predictor of the level of plant invasion, expressed as the proportion of alien to all species. At local scale, habitat types explain the level of invasion much better than alien propagule pressure. Moreover, it has been shown that patterns of habitat invasion are consistent among European regions with contrasting climates, biogeography, history and socioeconomic background. Here we use these findings as a basis for mapping the level of plant invasion in Europe. Location: European Union and some adjacent countries. Methods: We used 52,480 vegetation plots from Catalonia (NE Spain), Czech Republic and Great Britain to quantify the levels of invasion by neophytes (alien plant species introduced after ad 1500) in 33 habitat types. Then we estimated the proportion of each of these habitat types in CORINE land-cover classes and calculated the level of invasion for each class. We projected the levels of invasion on the CORINE land-cover map of Europe, extrapolating Catalonian data to the Mediterranean bioregion, Czech data to the Continental bioregion, British data to the British Isles and combined Czech-British data to the Atlantic and Boreal bioregions. Results: The highest levels of invasion were predicted for agricultural, urban and industrial land-cover classes, low levels for natural and semi-natural grasslands and most woodlands, and the lowest levels for sclerophyllous vegetation, heathlands and peatlands. The resulting map of the level of invasion reflected the distribution of these land-cover classes across Europe. Main conclusions: High level of invasion is predicted in lowland areas of the temperate zone of western and central Europe and low level in the boreal zone and mountain regions across the continent. Low level of invasion is also predicted in the Mediterranean region except its coastline, river corridors and areas with irrigated agricultural land. © 2008 The Authors.

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Prominent role of invasive species in avian biodiversity loss

Clavero M., Brotons L., Pons P., Sol D. (2009) Prominent role of invasive species in avian biodiversity loss. Biological Conservation. 142: 2043-2049.
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Doi: 10.1016/j.biocon.2009.03.034

Resum:

The rise of extinction rates associated with human activities has led to a growing interest in identifying extinction-prone taxa and extinction-promoting drivers. Previous work has identified habitat alterations and invasive species as the major drivers of recent bird extinctions. Here, we extend this work to ask how these human-driven impacts differentially affect extinction-prone taxa, and if any specific driver promotes taxonomic homogenization of avifauna. Like most previous studies, our analysis is based on global information of extinction drivers affecting threatened and extinct bird species from the IUCN Red List. Unlike previous studies, we employ a multivariate statistical framework that allows us to identify the main gradients of variation in extinction drivers. By using these gradients, we show that bird families with the highest extinction risk are primarily associated with threats posed by invasive species, once species richness and phylogeny are taken into account. As expected, the negative impact of invasive species was higher on island species, but our results also showed that it was particularly high in those species with small distribution ranges. On the other hand, mainland species and island species with large ranges tended to be affected by habitat destruction. Thus the impacts of invasive species promote the process of taxonomic homogenization among islands and between islands and continents. Consequently, introduced species may increase biotic homogenization not only directly, as generally believed, but also indirectly through their disproportional impact on endemic species imperilment. © 2009 Elsevier Ltd. All rights reserved.

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Pàgines