Der Wasserhaushalt der Nebelwälder im Schutzgebiet 'Bilsa' (Ecuador) und das Wiederaufforstungspotential angrenzender Weideflächen
When wind-driven fog meets an obstacle under favourable conditions, coagulation of droplets can result in a rain-like event, known by meteorologists as fog drip. Its ecological significance, however, is still subject of controversial discussion. If at all mentioned in the description of an ecosystem, fog drip would mostly be considered a relevant factor for epiphyte growth only, although some authors found amounts of fog drip as high as or even exceeding those of rain. Furthermore, it has not yet been investigated if plant design could have an influence on the individual fog drip efficiency – although it seems reasonable to assume that certain above-ground structures such as leaf shape or branch architecture have a significant impact. Within this complex, three aspects are being studied: a) A quantification of water flows in a cloud forest; b) Precipitation development of a reforestation plot in a foggy environment; c) Morphological characteristics that affect the fog drip efficiency of plants. Meteorological and hydrological data were collected over a one year period in a lower montane cloud forest of coastal Ecuador. Results are presented in a ´Klimadiagramm´ and a schematic flow chart. Precipitation at the investigated site was 900 mm of fog drip and 1925 mm of rain. Considering the fact that more than 90% of the fog drip was precipitated during the dry season, fog drip is identified as the main ecological factor for the region to sustain evergreen forests. From October 1999 until September 2000 precipitation and growth have been monitored at a reforestation plot. These measurements have shown that at a height of approximately 100 cm a process of self irrigation of the young trees sets in on fog events, resulting in considerably good conditions for reforestation in a region that so far has been described insufficiently in terms of its meteorological characteristics. In the discussion, fog drip is re-evaluated as an ecological factor for environments that experience frequent fog, focusing on hydro-ecological and biological consequences of the extensive deforestation in western Ecuador. Drip measurements under cut-off branches exposed to fog were carried out with woody plants on Tenerife and Ecuador, covering a wide range of morphological features. 6 factors are identified that are likely to have an impact on the plants’ fog drip efficiency: - Leaf Area Index: the more leaf area a plant produces in the canopy, the more surface can be exposed to the fog; - Compact Plant Architecture: densely constructed branches may shift air flow and inhibit the exposure of potentially fog-collecting plant surfaces; - Filling of Space: a regular distribution of fog-collecting surfaces enhances fog drip efficiency of branches that allow for a good air flow; - Leaf Structure: leaf roughness may increase its surface tension and thus enhance droplet run-off; - Leaf Stability: leaves that are attached loosely to the branch can easily turn sideways with the wind to minimize their flow resistance, exposing only a fraction of their surface; - Leaf Edge – Surface Ratio: small leaves show a better fog drip efficiency than big leaves, because they possess relatively more leaf edge areas, which appeared to be the main site of droplet coagulation. Based on the results of the drip measurements, an estimation of precipitation surplus caused by fog drip is given for the main forest types on Tenerife: 300 mm for laurel forest, 350 mm for pine forest and 450 mm for heath bushland, an increase of roughly 50% compared to a mean precipitation of 720 mm in the north of Tenerife.
info:eu-repo/classification/ddc/570, Biowissenschaften, Biologie, Mache-Chindul Nationalpark, Nebelwald, Wasserhaushalt, Klima
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