Publikationen
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Werner, F.A. & Homeier, J. (2024): Diverging elevational patterns of tree vs. epiphyte species density, beta diversity, and biomass in a tropical dry forest . Plants 13(18), 2555.
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DOI: 10.3390/plants13182555
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Abstract:
Abstract:
There is evidence to suggest that vascular epiphytes experience low competition for resources (light, water, and nutrients) compared to terrestrial plants. We tested the hypothesis that low resource competition may lead to higher nestedness among vascular epiphyte assemblages compared to trees. We studied the species composition and biomass of epiphytes and trees along an elevation gradient in a tropical dry forest in SW Ecuador. Both life-forms were inventoried on 25 plots of 400 m2 across five elevation levels (550–1250 m). Tree species density and total species richness increased with elevation, whereas basal area and biomass did not show significant trends. Epiphyte species density and richness both increased strongly with elevation, in parallel to biomass. Plot-level compositional changes were similarly strong for both life-forms. We attribute elevational increases in the species richness of trees and epiphytes to increasing humidity, i.e., more mesic growth conditions. We attribute the more pronounced elevational increase in epiphyte biomass, species density, and richness—the latter coupled with a higher degree of nestedness—to the greater moisture dependency of epiphytes and relatively low direct competition for resources. Our study provides a first comparison of elevational trends in epiphyte and tree diversity and biomass for a tropical dry forest.
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Keywords: |
biomass |
beta diversity |
species turnover |
Alpha diversity |
competition |
biotic interactions |
Knüsting, J.; Brinkmann, M.C.; Silva, B.; Schorsch, M.; Bendix, J.; Beck, E. & Scheibe, R. (2018): Who will win where and why? An ecophysiological dissection of the competition between a tropical pasture grass and the invasive weed Bracken over an elevation range of 1000m in the tropical Andes. PlosOne 13, 1-24.
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DOI: 10.1371/journal.pone.0202255
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Abstract:
Abstract:
In tropical agriculture, the vigorously growing Bracken fern causes severe problems by
invading pastures and out-competing the common pasture grasses. Due to infestation by
that weed, pastures are abandoned after a few years, and as a fatal consequence, the biodi-
versity-rich tropical forest is progressively cleared for new grazing areas. Here we present a
broad physiological comparison of the two plant species that are the main competitors on
the pastures in the tropical Ecuadorian Andes, the planted forage grass Setaria sphacelata
and the weed Bracken (Pteridium arachnoideum).With increasing elevation, the competitive
power of Bracken increases as shown by satellite data of the study region. Using data
obtained from field measurements, the annual biomass production of both plant species, as
a measure of their competitive strength, was modeled over an elevational gradient from
1800 to 2800 m. The model shows that with increasing elevation, biomass production of the
two species shifts in favor of Bracken which, above 1800 m, is capable of outgrowing the
grass. In greenhouse experiments, the effects on plant growth of the presumed key vari-
ables of the elevational gradient, temperature and UV radiation, were separately analyzed.
Low temperature, as well as UV irradiation, inhibited carbon uptake of the C4-grass more
than that of the C3-plant Bracken. The less temperature-sensitive photosynthesis of
Bracken and its effective protection from UV radiation contribute to the success of the weed
on the highland pastures. In field samples of Bracken but not of Setaria, the content of flavo-
noids as UV-scavengers increased with the elevation. Combining modeling with measure-
ments in greenhouse and field allowed to explain the invasive growth of a common weed in
upland pastures. The performance of Setaria decreases with elevation due to suboptimal
photosynthesis at lower temperatures and the inability to adapt its cellular UV screen.
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Keywords: |
South Ecuador |
Bracken fern |
competition |