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  • 1
    Electronic Resource
    Electronic Resource
    Natural 15N abundance of epiphytes depends on the position within the forest canopy: source signals and isotope fractionation (2002)
    Oxford, UK : Blackwell Science, Ltd
    Plant, cell & environment 25 (2002), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The natural 15N abundance (δ15N) of epiphytes and its N sources were studied in the canopy of a lowland rainforest in Costa Rica. Vascular and non-vascular epiphytes and canopy soils were collected from four canopy zones and analysed for N contents and δ15N signals. In addition, the N concentrations and δ15N signatures of bulk precipitation, throughfall and stemflow were measured during the wet and the dry season. The δ15N values of epiphyte leaves decreased significantly from the lower zones (means of −3·9 and −4·3‰) to the upper zones (means of −5·4 and −6·1‰) of the canopy. In contrast, δ15N signatures of canopy soils (average −0·3‰) differed little between the zones. Bulk deposition was enriched in 15N (+4·3‰) compared to all other potential N sources and was higher than throughfall and stemflow (+0·5 to −1·3‰). δ15N values of atmospheric deposition were inversely related to those of the epiphyte leaves, whereas N isotopic composition of canopy soils did not vary significantly. Consequently, it is concluded that the variations in foliar N isotope composition of epiphytes were not simply caused by utilization of isotopically different N sources, but by different 15N discrimination during N acquisition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00836.x
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  • 2
    Electronic Resource
    Electronic Resource
    Stable isotopic composition of carbon and nitrogen and nitrogen content in vascular epiphytes along an altitudinal transect* (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The foliar content of nitrogen and the relative abundances of 13C and 15N were analysed in vascular epiphytes collected from six sites along an altitudinal gradient from tropical dry forests to humid montane forests in eastern Mexico. The proportion of epiphyte species showing crassulacean acid metabolism (CAM) (atmospheric bromeliads, thick-leaved orchids, Cactaceae, and Crassulaceae) decreased with increasing elevation and precipitation from 58 to 6%. Atmospheric bromeliads, almost all of which had δ13C values indicating CAM, were more depleted in 15N (x=−10·9‰± 2·11) than the C3 bromeliads which form water-storing tanks (−6·05‰± 2·26). As there was no difference in δ15N values between C3 and CAM orchids, the difference in bromeliads was not related to photosynthetic pathways but to different nitrogen sources. While epiphytes with strong 15N depletion appear to obtain their nitrogen mainly from direct atmospheric deposition, others have access to nitrogen in intercepted water and from organic matter decomposing on branches and in their phytotelmata. Bromeliads and succulent orchids had a lower foliar nitrogen content than thin-leaved orchids, ferns and Piperaceae. Ground-rooted hemi-epiphytes exhibited the highest nitrogen contents and δ15N values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00502.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation between water relations and within-canopy distribution of epiphytic ferns in a Mexican cloud forest (1998)
    Springer
    Oecologia 114 (1998), S. 305-316 
    Details
    ISSN: 1432-1939
    Keywords: Key words Fern ; Epiphyte ; Cloud forest ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physiological traits associated with water relations of eight common epiphytic ferns in a Mexican cloud forest were investigated in relation to the distribution of these species within the canopy. Fern distribution was significantly correlated with the relative water content at which stomata close, leaf thickness, stomatal density and size. Trichomanes bucinatum desiccated completely within hours in moderately dry air and was confined to the stem bases, and Asplenium cuspidatum, with no evident adaptations to cope with drought, grew in the second most shaded zone within the tree crowns. Despite growing in a humid cloud forest, all other species had xeric adaptations including coriaceous leaves (Pleopeltis mexicana, Elaphoglossum glaucum), succulent rhizomes (Polypodium puberulum, Phlebodium areolatum), low rates of uncontrolled water loss (all species except P. puberulum), leaf scales (Elaphoglossum petiolatum, Polypodium plebeium), and high cell wall elasticity (all species). P. plebeium and Pl. mexicanum, which grow in the most exposed locations, tolerated water loss beyond the turgor loss point before the stomata closed and appear to be poikilohydric or at least to tolerate high water deficits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050452
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    Paper (German National Licenses)
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