1,720,994 research outputs found
Tree rings indicate different drought resistance of a native (Abies alba Mill.) and a nonnative (Picea abies (L.) Karst.) species co-occurring at a dry site in Southern Italy
No full textClimate changes induced by the anthropogenic alteration of the atmospheric radiative balance are expected to change the productivity and composition of forest ecosystems. In Europe, the Mediterranean is considered one of the most vulnerable regions according to climatic forecasts and simulations. However, although modifications in the inter-specific competition are envisaged, we still lack a clear understanding of the ability of the Mediterranean vegetation to adapt to climate changes. We investigated how two co-occurring tree species commonly used in afforestation programmes, the native Abies alba Mill. and the nonnative Picea abies L. Karst., adapt to climate change by assessing their growth performance and physiological responses in relation to past climate variability. Growth was addressed by analysing tree-ring width and carbon and oxygen stable isotopes. Statistical relationships between isotopic value and monthly climate data suggest that the two species underwent ecophysiological adaptation to Mediterranean climatic constraints. These adaptations are also expressed in the ring-width data. Based on the carbon isotope ratio reflecting the stomatal response to drought, we found that the precipitation in the first period of the growing season, i.e. early spring, is a major factor influencing the annual growth of A. alba, which although native, proved to be sensitive to drought. P. abies, on the other hand, showed a higher tolerance to summer drought stress. These findings should help define criteria for sustainability and effective forest conservation in the Mediterranean region. © 2008 Elsevier B.V. All rights reserved
Inter-comparison of methods for quantifying above-ground leaf litter decomposition rates
No full textMonitoraggio della Biodiversità floristica e dello stato del suolo in un sistema costiero mediterraneo
No full textThe response of photosynthesis and stomatal conductance of forest trees exposed to elevated CO2: δ13C and δ18O tree ring analysis
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Climatic sensitivity of δ18O in the wood and cellulose of tree rings: Results from a mixed stand of Acer pseudoplatanus L. and Fagus sylvatica L.
No full textThe oxygen isotope composition in tree rings is commonly used to assess the impact of climatic factors on tree growth. However, the relationships between environmental variables and δ18O in whole wood and the wood components (e.g., cellulose, lignin) are still not completely clear - particularly for deciduous species. It is currently common procedure to consider only one wood constituent, a process that saves time. To test whether the δ18O of cellulose relates better to environmental variables than that of whole wood, we measured the oxygen isotopic composition of tree ring whole wood and cellulose, for the period 1916-1950, for two different broad-leaved species (Fagus sylvatica L. and Acer pseudoplatanus L.) on Monti Picentini (Southern Italy). Data show that δ18O in cellulose is enriched (4.7 ± 1.1‰) compared to the corresponding whole wood. The relationship between the δ18O of the cellulose and of whole wood is generally poor, especially for A. pseudoplatanus suggesting that the sources of variability for δ18O differ strongly between the whole wood and the cellulose constituents. Furthermore, we find that the cellulose fraction correlates strongly with climatic variables, while the whole wood fraction generally does not. Monthly temperature during the growing season is strongly correlated with δ18O of cellulose for F. sylvatica (r = 0.82) and A. pseudoplatanus (r = 0.63) but not with δ18O of whole wood. We found a relevant difference in the isotopic signals of the two species that could be related with difference in seasonal timing of growth. In contrast to F. sylvatica, early spring conditions have an influence on A. pseudoplatanus at our study site. This is evidenced by the high correlation between δ18O of cellulose and April and May precipitation, and the positive relationship between tree ring width and March and April mean annual temperature. The different climatic sensitivities of the two investigated species suggest that physiological properties, i.e. root system and stomatal conductance responses, or a variation in the proportions of wood constituents play an important role for the oxygen isotopic signal. We conclude that, even when partially obscured by site parameters (soil depth and structure, nutrient availability, etc.), δ18O in the cellulose compartment strongly reflects climate information. Our study suggests that cellulose extraction is a necessary step in studies seeking to investigate the climatic signatures in the δ18O of broad-leaved species. © 2008 Elsevier B.V. All rights reserved
Tree rings stable C isotopes as indicators of climatic change in the Mediterranean basin.
No full textDecreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland
No full textPrecipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks. © Author(s) 2011
Complex interaction between litter decomposition and rhizosphere activity revealed by novel experimental approach
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