<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Pacheco-Labrador, Javier</style></author><author><style face="normal" font="default" size="100%">González-Cascón, Rosario</style></author><author><style face="normal" font="default" size="100%">Martín, M Pilar</style></author><author><style face="normal" font="default" size="100%">Riaño, David</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Understanding the optical responses of leaf nitrogen in Mediterranean Holm oak (Quercus ilex) using field spectroscopy</style></title><secondary-title><style face="normal" font="default" size="100%">International Journal of Applied Earth Observation and Geoinformation</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Field spectroscopy</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf nitrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">Spectral index</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2014</style></year></dates><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">105-118</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The direct estimation of nitrogen (N) in fresh vegetation is challenging due to its weak influence on leaf reflectance and the overlaps with absorption features of other compounds. Different empirical models relate in this work leaf nitrogen concentration ([N]Leaf) on Holm oak to leaf reflectance as well as derived spectral indices such as normalized difference indices (NDIs), the three bands indices (TBIs) and indices previously used to predict leaf N and chlorophyll. The models were calibrated and assessed their accuracy, robustness and the strength of relationship when other biochemicals were considered. Red edge was the spectral region most strongly correlated with [N]Leaf, whereas most of the published spectral indexes did not provide accurate estimations. NDIs and TBIs based models could achieve robust and acceptable accuracies (TBI1310,1720,730: R2 = 0.76, [0.64,0.86]; RMSE (%) = 9.36, [7.04,12.83]). These models sometimes included indices with bands close to absorption features of N bonds or nitrogenous compounds, but also of other biochemicals. Models were independently and inter-annually validated using the bootstrap method, which allowed discarding those models non-robust across different years. Partial correlation analysis revealed that spectral estimators did not strongly respond to [N]Leaf but to other leaf variables such as chlorophyll and water, even if bands close to absorption features of N bonds or compounds were present in the models.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Körner, C</style></author><author><style face="normal" font="default" size="100%">Miglietta, Francesco</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Long term effects of naturally elevated CO 2 on mediterranean grassland and forest trees</style></title><secondary-title><style face="normal" font="default" size="100%">Oecologia</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbohydrates</style></keyword><keyword><style  face="normal" font="default" size="100%">Global change</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf nitrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">natural-co2 springs</style></keyword><keyword><style  face="normal" font="default" size="100%">photosynthesis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><volume><style face="normal" font="default" size="100%">99</style></volume><pages><style face="normal" font="default" size="100%">343-351</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We investigated the carbon supply status in species-rich mediterranean plant communities growing in a bowl-shaped 1-ha &quot;CO2 spring&quot; area near Sienna, Italy. A geothermic &quot;lime-kiln&quot; has provided these communities, for as long as historical records are avail- able, with pure CO2 that mixes with ambient air at canopy level to daytime means of 500-1000 ppm CO2. Immediately outside the spring area similar plant com- munities are growing on similar substrate, and in the same climate, but under ca. 355 ppm CO2. We found no evidence that plants in the CO2 spring area grow faster, flower earlier or become larger. However, we found very large differences in tissue quality among the 40 species studied inside and outside the spring area. Depending on weather conditions, the mean concentra- tion of total non-structural carbohydrates (TNC, sugars and starch) in leaves of herbaceous plants was 38-47% higher in the spring area. Fast growing ruderals growing on garden soil inside and outside the spring area show the same response. Among trees, leaves of the deciduous Quercus pubscens contain twice as much TNC inside as outside the vent area, whereas evergreen Q. ilex leaves show no significant difference. TNC levels in branch wood paralleled leaf values. TNC in shade leaves was also higher. Elevated CO2 had no effect on the sugar fraction, therefore differences in TNC are due to starch accumulation. Leaf nitrogen concentration decreases under elevated CO2. These observations suggest that the commonly reported TNC accumulation and N depletion in leaves growing under elevated CO2 are not restricted to the artificial condi- tions of short-term COz enrichment experiments but persist over very long periods. Such an alteration of tissue composition can be expected to occur in other plant communities also if atmospheric COz levels con- tinue to rise. Effects on food webs and nutrient cycling are likely</style></abstract></record></records></xml>