Biologie d'une espèce endémique à aire restreinte: Centaurea corymbosa Pourret. Conséquences pour sa conservation.

Colas B, Riba M, Olivieri I, Ronce O, Henry JP (1999) Biologie d'une espèce endémique à aire restreinte: Centaurea corymbosa Pourret. Conséquences pour sa conservation. Bulletin de la Société Botanique du Centre-Ouest 19: 279-293.

Variability of plant nitrogen and water use in a 100-m transect of a subdesertic depression of the Ebro valley (Spain) characterized by leaf δ13C and δ15N

Peñuelas J., Filella I., Terradas J. (1999) Variability of plant nitrogen and water use in a 100-m transect of a subdesertic depression of the Ebro valley (Spain) characterized by leaf δ13C and δ15N. Acta Oecologica. 20: 119-123.
Enllaç
Doi: 10.1016/S1146-609X(99)80024-1

Resum:

We studied carbon and nitrogen isotopic composition (δ13C and δ15N) in sunlit leaves of four dominant species (Rosmarinus officinalis L., Stipa parviflora L., Juniperus thurifera L. and Pinus halepensis L.) in a characteristic gradient of water and nitrogen availability produced by relief and micrometeorology in a subdesertic valley of central-NE Spain. Minimum values of δ13C were found at the foothills, and higher values were found both in the valley and oil the top of the hill where water availability was lower. However, different species (functional groups) presented different δ13C values in the same valley. The lowest values of δ15N were found on the top of the hill and the highest ones in the valley, where N losses would thus be higher. In general, when growing together, trees showed 2 ‰ higher values for δ13C as well as for δ15N than shrubs and grasses. The specific responses show that they use different available water and nitrogen resources within small catchments. For this ecosystem type, C and N isotope analyses are sensitive enough to resolve fine spatial and functional patterns even over a very short distance (100 m), where topography generates great gradients in microclimate, hydrology, soil physical conditions, vegetation and biogeochemistry.

Llegeix més

Reflectance indices indicative of changes in water and pigment contents of peanut and wheat leaves

Peñuelas J., Inoue Y. (1999) Reflectance indices indicative of changes in water and pigment contents of peanut and wheat leaves. Photosynthetica. 36: 355-360.
Enllaç
Doi: 10.1023/A:1007033503276

Resum:

Measurements of reflectance in visible and near-infrared spectral regions were made on detached leaves of two crop species of different leaf morphology, structure, and water content (peanut and wheat) throughout progressive desiccation. Relative water content (RWC) was well correlated with water index (WI) but even better with the ratio of WI and normalized difference vegetation index. RWC was also significantly correlated with structural independent pigment index indicative of carotenoids/chlorophyll ratio. New indication is thus provided to assess leaf water content and apply simple and fast radiometric techniques for plant water stress management.

Llegeix més

Short-term responses of terpene emission rates to experimental changes of PFD in Pinus halepensis and Quercus ilex in summer field conditions

Peñuelas J., Llusià J. (1999) Short-term responses of terpene emission rates to experimental changes of PFD in Pinus halepensis and Quercus ilex in summer field conditions. Environmental and Experimental Botany. 42: 61-68.
Enllaç
Doi: 10.1016/S0098-8472(99)00018-0

Resum:

The diurnal relationships of monoterpene emission with PFD and photosynthetic rates were studied in the Mediterranean trees Pinus halepensis, a terpene storing species, and Quercus ilex, a non-storing species, under summer field conditions. At morning, midday and evening, leaves were submitted to different irradiance levels by differentially shading them. Both species emitted large amounts of monoterpenes (about 20 μg g DM-1 h-1). The most emitted terpene by P. halepensis was Δ3-carene followed by β-myrcene, α-pinene and β-pinene. The most emitted terpene by Q. ilex was limonene followed by α-pinene and α-pinene. No clear correlation to temperature was found for Q. ilex emission within the diurnal range of 21-33°C, whereas P. halepensis emissions increased with the temperature. There was no consistent link between terpene emissions and PFD or photosynthetic rates for P. halepensis but there were significant relationships for Q. ilex. However, emissions by Q. ilex became inhibited at highest PFDs and during the course of the day when net photosynthesis decreased under summer drought. The study shows that the emission rates of both species are highly variable and that during a hot Mediterranean summer day (with limited water availability) the diurnal variation of emission is not only driven by the common light and temperature dependencies. Water stress, branch-to-branch variability and other influences must explain great part of the observed variability.

Llegeix més

Dependence of ozone biomonitoring on meteorological conditions of different sites in Catalonia (N.E. Spain)

Peñuelas J., Ribas A., Gimeno B.S., Filella I. (1999) Dependence of ozone biomonitoring on meteorological conditions of different sites in Catalonia (N.E. Spain). Environmental Monitoring and Assessment. 56: 221-224.
Enllaç
Doi: 10.1023/A:1006062613552

Resum:

Evaluation of visual symptoms of ozone damage was conducted in the network of bioindicater rural stations of Catalonia (NE Spain) every 14 days from May to October. Damage rates of ozone (and consequently, ozone biomonitoring capacity of bioindicators) were found to vary highly in time and space depending on the local environmental and meteorological conditions. Lower ozone damage to foliage was produced when meteorological conditions favour stomata resistance. Modulatory effects of meteorological conditions need to be considered in biomonitoring and when modeling plant ozone doses and damage.

Llegeix més

Soil arthropods.

Andrés P, Mateos E, Ascaso C (1999) Soil arthropods. In Rodà F, Retana J, Gracia C, Bellot J (eds) Ecology of Mediterranean evergreen oak forests. Springer, Berlin, pp. 341-354.

Ecological risks of the use of sewage sludge as fertilizer in soil restoration: Effects on the soil microarthropod populations.

Andrés P (1999) Ecological risks of the use of sewage sludge as fertilizer in soil restoration: Effects on the soil microarthropod populations. Land Degradation & Development 10:67-77.

Leaf traits and canopy organization.

Sabaté S, Sala A, Gracia C (1999) Leaf traits and canopy organization. In Rodà F, Retana J, Gracia C, Bellot J (eds) Ecology of Mediterranean evergreen oak forests. Springer, Berlin, pp. 121-133.

Lasius neglectus Van Loon, Boomsma & Andrásfalvy, 1990 (Hymenoptera, Formicidae), a potential pest ant in Spain.

Espadaler X (1999) Lasius neglectus Van Loon, Boomsma & Andrásfalvy, 1990 (Hymenoptera, Formicidae), a potential pest ant in Spain. Orsis 14:43-46.

Les lleteres, unes plantes que paguen peatge.

Espadaler X (1999) Les lleteres, unes plantes que paguen peatge. Brots de Collserola 77:775-778.

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