Peuelas J., Filella I. (2002) Metal pollution in Spanish terrestrial ecosystems during the twentieth century. Chemosphere. 46: 501-505.EnllaçDoi: 10.1016/S0045-6535(01)00171-0
We show here additional biological evidence of the alteration in global biogeochemistry by human activities during the twentieth century. The mineral concentration of herbarium specimens of 24 species of vascular plants and three species of bryophytes collected in North and East regions of Spain have substantially changed throughout the twentieth century. While V, a proxy tracer of oil pollution, exponentially increased in the last decades, other metals such as Cr, Ba, Sr, Al, Fe, Pb, Cd and Ti increased up to 1960-1970 and started to decrease in 1985-1995, when environmental legal regulations started to be effective. Multivariate principal component analysis showed an overall change in plant elemental concentrations throughout the different decades of the century and a clear separation of vascular plants and bryophytes. Likely important consequences for ecosystem structure and functioning and even for human health may be expected from these changes in mineral concentration. © 2002 Elsevier Science Ltd. All rights reserved.
Peñuelas J., Filella I., Comas P. (2002) Changed plant and animal life cycles from 1952 to 2000 in the Mediterranean region. Global Change Biology. 8: 531-544.EnllaçDoi: 10.1046/j.1365-2486.2002.00489.x
The available data on climate over the past century indicate that the earth is warming. Important biological effects, including changes of plant and animal life cycle events, have already been reported. However, evidence of such effects is still scarce and has been mostly limited to northern latitudes. Here we provide the first long-term (1952-2000) evidence of altered life cycles for some of the most abundant Mediterranean plants and birds, and one butterfly species. Average annual temperatures in the study area (Cardedeu, NE Spain) have increased by 1.4 °C over the observation period while precipitation remained unchanged. A conservative linear treatment of the data shows that leaves unfold on average 16 days earlier, leaves fall on average 13 days later, and plants flower on average 6 days earlier than in 1952. Fruiting occurs on average 9 days earlier than in 1974. Butterflies appear 11 days earlier, but spring migratory birds arrive 15 days later than in 1952. The stronger changes both in temperature and in phenophases timing occurred in the last 25 years. There are no significant relationships among changes in phenophases and the average date for each phenophase and species. There are not either significant differences among species with different Raunkiaer life-forms or different origin (native, exotic or agricultural). However, there is a wide range of phenological alterations among the different species, which may alter their competitive ability, and thus, their ecology and conservation, and the structure and functioning of ecosystems. Moreover, the lengthening of plant growing season in this and other northern hemisphere regions may contribute to a global increase in biospheric activity.
Peñuelas J, Filella I, Tognetti R (2001) Leaf mineral concentrations of Erica arborea, Juniperus communis and Myrtus communis growing in the proximity of a natural CO2 spring. Global Change Biology 7:291-301.
Peñuelas J, Filella I (2001) Responses to a warming world. Science 294:793-795.
Peñuelas J., Filella I. (2001) Phenology: Responses to a warming world. Science. 294: 793-795.EnllaçDoi: 10.1126/science.1066860
[No abstract available]
Peñuelas J., Filella I. (2001) Herbaria century record of increasing eutrophication in Spanish terrestrial ecosystems. Global Change Biology. 7: 427-433.EnllaçDoi: 10.1046/j.1365-2486.2001.00421.x
Additional biological evidence is presented for the alteration of biogeochemical cycles by human activities. The leaf δ15N and the concentrations of nutrients in herbarium specimens of 24 species of vascular plants and 3 species of bryophytes collected in northern and eastern regions of Spain have substantially changed throughout the XX century. In the second half of the century, when anthropogenic nitrogen fixation and mobilization started to increase rapidly, leaf δ15N values started to decrease strongly, indicating that additional anthropogenic nitrogen is being retained in Spanish terrestrial ecosystems. The concentration of nutrients in vascular plants did not present any clear pattern, but there were increasing concentrations of N and other nutrients (P, K, and S) in the last decades in bryophytes, which are usually better biomonitors of airborne chemicals than vascular plants. Important consequences for ecosystem structure and functioning such as enhancement of the carbon sink or changes in community biodiversity and species distribution may be expected from this increase in eutrophication.
Serrano L, Filella I, Peñuelas J (2000) Remote sensing of biomass and yield of winter wheat under different nitrogen supplies. Crop Science 40:723-731.
Peñuelas J, Filella I, Piñol J, Siscart D, Lloret F (2000) Effects of a severe drought on water and nitrogen use by Quercus ilex and Phillyrea latifolia. Biologia Plantarum 43:47-53.
Filella I., Peñuelas J. (1999) Altitudinal differences in UV absorbance, UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region. Plant Ecology. 145: 157-165.EnllaçDoi: 10.1023/A:1009826803540
We studied the variations in different physiological parameters associated with UV-B radiation defense: UV-B radiation absorbance, UV-visible spectral reflectance, carotenoids concentration, leaf thickness, SLW (specific leaf weigth) and trichome density in Quercus ilex growing at 200 and 1200 m and Rhododendron ferrugineum growing at 2200 m. We examined the role of these parameters as protection mechanisms in an altitudinal gradient of increasing UV radiation in northern Catalonia and in sun and shade leaves. The concentration of UV-B radiation absorbing pigments was 15% higher in sun leaves of Q. ilex at 1200 m than in those from 200 m altitude. Sun leaves of R. ferrugineum presented concentrations three times higher than those of Q. ilex. Reflectance ranged between 5% (in the region 300-400 nm) and 12% (in the region 280-300 nm). The variation of reflectance with altitude followed an inverse trend respect to absorbance in the 280-300 nm region, with higher values the lower the altitude, but in the 300-400 nm region, reflectance of the lower site was the lowest. In both species and altitudes sun leaves presented higher concentrations of UV-B radiation absorbing pigments and UV reflectance than shade leaves. Quercus ilex trees of the higher location presented higher NDPI (Normalized Difference Pigment Reflectance Index) values, indicating higher carotenoids/chlorophyll a ratio. Actual measurements of carotenoid/chlorophyll a ratio confirmed this pattern. The photochemical reflectance index (PRI) presented higher values the higher the location indicating lower photosynthetic radiation-use efficiency. Specific leaf weight (SLW) and leaf thickness were larger in Q. ilex trees of higher location than in those of lower location. In both sites, sun leaves also presented larger SLW values than shade leaves. Adaxial leaf hair density in sun leaves was significantly higher in the lower location. UV absorption and linked morphological traits (SLW, leaf thickness measured in Q. ilex) presented the larger differences among studied plants at different altitudes and seem to be the dominant UV protecting mechanisms.
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.EnllaçDoi: 10.1016/S1146-609X(99)80024-1
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.
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