Nutrient availability and climate as the main determinants of the ratio of biomass to NPP in woody and non-woody forest compartments

Fernández-Martínez M., Vicca S., Janssens I.A., Campioli M., Peñuelas J. (2016) Nutrient availability and climate as the main determinants of the ratio of biomass to NPP in woody and non-woody forest compartments. Trees - Structure and Function. 30: 775-783.
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Doi: 10.1007/s00468-015-1319-8

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Key message: Once the effect of stand age has been taken into account, nutrient availability and climate play a crucial role in determining the B:NPPs of woody and non-woody tissues. Abstract: Forest ecosystems accumulate large amounts of carbon in living tissues. The residence time of this carbon in the ecosystem depends largely on the turnover time of these tissues, which can be estimated as a surrogate of the ratio of biomass to net primary production (B:NPP). We used a global forest database of 310 sites containing data for biomass stocks and NPP to investigate the differences of B:NPPs among species and forest compartments and to determine B:NPPs main exogenous (mainly climate and nutrient availability) and endogenous (leaf habit and stand age) drivers. We used asymptotic exponential functions to adjust the B:NPPs of woody compartments to a theoretical stationary state to allow comparisons between forests of different ages. The B:NPPs of woody tissues (branches, stems, and coarse roots) were positively influenced by stand age, conversely to fine roots and leaves, which were weakly dependent on the age of the forest. The B:NPPs of woody tissues were positively correlated with nutrient availability, whereas fine-root B:NPPs decreased with increasing nutrient availability. The foliar B:NPP of evergreen forests was positively correlated with water deficit, and the fine-root B:NPP was correlated positively with the seasonality of precipitation and with annual thermal amplitude but negatively with water deficit. Our results support the influence of climate on the B:NPPs of non-woody compartments and identify nutrient availability as the main influence on the B:NPPs of woody tissues. © 2015, Springer-Verlag Berlin Heidelberg.

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The North Atlantic Oscillation synchronises fruit production in western European forests

Fernández-Martínez M., Vicca S., Janssens I.A., Espelta J.M., Peñuelas J. (2016) The North Atlantic Oscillation synchronises fruit production in western European forests. Ecography. : 0-0.
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Doi: 10.1111/ecog.02296

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Weather and its lagged effects have been associated with interannual variability and synchrony of fruit production for several tree species. Such relationships are used often in hypotheses relating interannual variability in fruit production with tree resources or favourable pollinating conditions and with synchrony in fruit production among sites through the Moran effect (the synchronisation of biological processes among populations driven by meteorological variability) or the local availability of pollen. Climatic teleconnections, such as the North Atlantic Oscillation (NAO), representing weather packages, however, have rarely been correlated with fruit production, despite often being better predictors of ecological processes than is local weather. The aim of this study was to test the utility of seasonal NAO indices for predicting interannual variability and synchrony in fruit production using data from 76 forests of Abies alba, Fagus sylvatica, Picea abies, Pseudotsuga menziesii, Quercus petraea, and Q. robur distributed across central Europe. Interannual variability in fruit production for all species was significantly correlated with seasonal NAO indices, which were more prominently important predictors than local meteorological variables. The relationships identified by these analyses indicated that proximal causes were mostly responsible for the interannual variability in fruit production, supporting the premise that local tree resources and favourable pollinating conditions are needed to produce large fruit crops. Synchrony in fruit production between forests was mainly associated with weather and geographical distance among sites. Also, fruit production for a given year was less variable among sites during warm and dry springs (negative spring NAO phases). Our results identify the Moran effect as the most likely mechanism for synchronisation of fruit production at large geographical scales and the possibility that pollen availability plays a role in synchronising fruit production at local scales. Our results highlight the influence of the NAO on the patterns of fruit production across western Europe. © 2016 Nordic Society Oikos.

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The role of nutrients, productivity and climate in determining tree fruit production in European forests

Fernández-Martínez, M., Vicca, S., Janssens, I.A., Espelta, J.M., Peñuelas, J. (2016) The role of nutrients, productivity and climate in determining tree fruit production in European forests. New Phytologist. : 0-0.
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Doi: 10.1111/nph.14193

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Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia

Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Rico, L., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino, M., Vives, M., Nadal-Sala, D., Sabaté, S., Gracia, C., Terradas, J. (2016) Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia. Environmental and Experimental Botany. : 0-0.
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Doi: 10.1016/j.envexpbot.2017.05.012

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Factors influencing the foliar elemental composition and stoichiometry in forest trees in Spain

Sardans J., Alonso R., Carnicer J., Fernández-Martínez M., Vivanco M.G., Peñuelas J. (2016) Factors influencing the foliar elemental composition and stoichiometry in forest trees in Spain. Perspectives in Plant Ecology, Evolution and Systematics. 18: 52-69.
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Doi: 10.1016/j.ppees.2016.01.001

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Concentrations of nutrient elements in organisms and in the abiotic environment are key factors influencing ecosystem structure and function. We studied how concentrations and stoichiometries of nitrogen (N), phosphorus (P) and potassium (K) in leaves of forest trees are related to phylogeny and to environmental factors (mean annual precipitation, mean annual temperature, forest type, and nitrogen deposition). Using data for 4691 forest plots from across Spain, we tested the following hypotheses: (i) that foliar stoichiometries of forest trees are strongly influenced by phylogeny, (ii) that climate, as an important driver of plant uptake and nutrient use efficiency, affects foliar stoichiometry, (iii) that long-term loads of N influence N, P and K concentrations and ratios in natural vegetation, and (iv) that sympatric species are differentiated according to their foliar stoichiometry, thereby reducing the intensity of resource competition. Our analyses revealed that several factors contributed to interspecific variation in elemental composition and stoichiometry. These included phylogeny, forest type, climate, N deposition, and competitive neighborhood relationships (probably related to niche segregation effect).These findings support the notion that foliar elemental composition reflects adaptation both to regional factors such as climate and to local factors such as competition with co-occurring species. © 2016 Elsevier GmbH.

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