Sabaté S., Gracia C.A., Sánchez A. (2002) Likely effects of climate change on growth of Quercus ilex, Pinus halepensis, Pinus pinaster, Pinus sylvestris and Fagus sylvatica forests in the Mediterranean region. Forest Ecology and Management. 162: 23-37.EnllaçDoi: 10.1016/S0378-1127(02)00048-8
Mediterranean forest growth is constrained by drought and high temperatures during summer. Effects of climate change on these forests depend on how changes in water availability and temperature will take place. A process-based forest growth model, growth of trees is limited by water in the Mediterranean (GOTILWA+), was applied in the Mediterranean region on Quercus ilex, Pinus halepensis, P. pinaster, P. sylvestris and Fagus sylvatica forests. The effects of climate change on growth were analysed, as well as the effect of thinning cycle length, combined with the assumption of different soil depths. Thinning cycle lengths was included because it can affect the response of stands to climatic conditions, and soil depth because this is positively related to soil water-holding capacity and consequently may change the effects of drought. The simulation period covered 140 years (1961-2100). Model results show that leaf area index (LAI) may increase, favoured by the increase of atmospheric CO2, particularly at sites where rainfall is relatively high and climatic conditions not too warm. The predicted increase in temperature significantly influenced mean leaf life span (MLLS). MLLS of F. sylvatica would increase with climate change, implying a longer growing period. Conversely, MLLS of evergreen species would be reduced, accelerating leaf turnover. In general, our results showed a higher production promoted by projected climate change in response to the increasing atmospheric CO2 concentration and rainfall in the region. Temperature increase would have different consequences for production. In F. sylvatica, the longer growing period would promote higher production, particularly when water is not limiting. On the other hand, Q. ilex and Pinus species would expend more carbon in maintaining and producing leaves to replace those lost in increased turnover rate. As expected, access of roots to deeper soil results in an increased final wood yield (FWY) due to an improved water balance that promotes higher transpiration, photosynthesis and growth. In general, the shorter the harvest cycle, the larger the FWY, because of less tree mortality between harvesting events. According to our results, temperature and rainfall may constrain growth during certain periods but if rainfall increases in the future, a positive effect on growth is likely. © 2002 Elsevier Science B.V. All rights reserved.
Serrano L., Peñuelas J., Ustin S.L. (2002) Remote sensing of nitrogen and lignin in Mediterranean vegetation from AVIRIS data: Decomposing biochemical from structural signals. Remote Sensing of Environment. 81: 355-364.EnllaçDoi: 10.1016/S0034-4257(02)00011-1
Remote sensing estimates of vegetation nitrogen (N) and lignin concentration are central to assess ecosystem processes such as growth and decomposition. Although remote sensing techniques have been proven useful to assess N and lignin contents in continuous green canopies, more studies are needed to address their capabilities, particularly in low and sparsely vegetated ecosystems. We investigated the possibility of estimating canopy N and lignin concentrations in chaparral vegetation using Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) reflectance acquired over an area around Point Dume in the Santa Monica Mountains (Los Angeles, CA, USA). Two approaches were tested: multiple stepwise regression based on first difference reflectance (FDR) and reflectance (R) indices. Multiple stepwise regressions (of three or fewer wavelengths) accounted for a large variance in canopy biochemical concentration (r2 ∼ 0.9, P < 0.01). Log transformed R indices [log (1/R)] formulated on the basis of previously known N and lignin absorption wavelengths also showed significant correlations (P < 0.01) with canopy biochemical concentration (r2 ranging from 0.39 to 0.48). In addition, the contribution of structural and biochemical signals and background effects on the performance of these indices was evaluated. These indices accounted for a increased variance when adding information on canopy structural attributes (e.g., relative contribution of each species and biomass amount) to foliar biochemical concentration. The relative contributions of foliar biochemical concentration and canopy structure (biomass amount) on the spectral signal were further evaluated by analyzing the residuals from linear regressions: foliar N concentration accounted for 42% of the variance for a normalized difference index based on the 1510-nm N absorption feature, while the foliar lignin concentration accounted for 44% of the variance for a normalized difference index based on the 1754 nm lignin absorption feature. These percentages increased to 58% when stands with senescing vegetation were disregarded. We propose the two indices, Normalized Difference Nitrogen Index (NDNI = [log (1/R1510)-log (1/R1680)]/[log (1/R1510)+log (1/R1680)]) and Normalized Difference Lignin Index (NDLI = [log (1/R1754)-log (1/R1680)]/[log (1/R1754)+log (1/R1680)]) as indices to assess N and lignin in native shrub vegetation. © 2002 Elsevier Science Inc. All rights reserved.
Billen J, Espadaler X (2002) A novel epithelial intramandibular gland in the ant Pyramica membranifera (Hymenoptera, Formicidae). Belgian Journal of Zoology 132:175-176.
Boieiro M, Espadaler X, Azedo AR, Serrano ARM (2002) Four new species to the ant fauna of Portugal (Hymenoptera, Formicidae). Boletim da Sociedade Portuguesa de Entomologia 202:253-259.
Espadaler X, Gómez C (2002) The species body-size distribution in Iberian ants is parameter independent. Vie et Milieu 52:103-107.
Espadaler X, Rojo M (2002) Lasius brunneus, una formiga autòctona, plaga del suro. Full Informatiu 1, Centre de la Propietat Forestal.
Espadaler X, Espejo F (2002) Tapinoma melanocephalum (Fabricius, 1793), a new exotic ant in Spain (Hymenoptera, Formicidae). Orsis 17:1001-104.
Espadaler X (2002) La hormiga faraón, Monomorium pharaonis (L.), en España y Portugal es, aparentemente, un mito. Pest Control News 5:26.
Espadaler X, Akino T, Terayama M (2002) Specific status for Lasius nipponensis Forel, 1912 (Hymenoptera, Formicidae). Nouvelle Revue Entomologique 18:335-341.
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