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- Fog precipitation and rainfall interception in the natural forests of Madeira Island (Portugal)Publication . Prada, Susana; Sequeira, Miguel Menezes de; Figueira, Celso; Silva, Manuel Oliveira daSituated in the Atlantic Ocean, Madeira is a within-plate volcanic island, approximately 600 km northwest of the Western African coast. Cloud cover formed mainly of orographic origin persists on Madeira for more than 200 days per year between 800 m and 1600 m altitude. Since vegetation occupies 2/3 of the island’s surface, fog precipitation, which occurs when fog droplets are filtered by the forest canopy and coalesce on the vegetation surfaces to form larger droplets that drip to the forest floor, is an important hydrological input. Rainfall interception and fog precipitation data were collected between 1996 and 2005 in the natural forests of Madeira. Six throughfall gauges were placed under the canopy of three different types of forest: high altitude tree heath forest (1580 m), secondary tree heath forest (1385 m) and humid laurisilva forest (1050 m). Fog precipitation is higher under high altitude heath forest (average canopy interception was 225% of gross precipitation) and dependent both on altitude and vegetation type, due to different tree architecture and leaf shape. Although results are conservative estimates of fog precipitation, they point towards the importance of fog-water as a source of groundwater recharge in the water balance of the main forest ecosystems of Madeira.
- Response to “Comment on fog precipitation and rainfall interception in the natural forests of Madeira Island (Portugal)”Publication . Prada, Susana; Sequeira, Miguel Menezes de; Figueira, Celso; Prior, Víctor; Silva, Manuel Oliveira daIn this paper we discuss the comments given by Regalado and Ritter (2010) on our previous work (Prada et al., 2009). Here, we demonstrate that rainfall correction does not significantly change the results; make clear why Site 1’s fog precipitation values do not seem to be overestimated due to the low number of gauges; present observational evidence that suggest high water yields in Site 1; and why we consider that fog water may be important for groundwater recharge. We also review different methodological, ecological and climatic factors between Madeira and the Canary Islands’ fog precipitation studies that might explain different values between them (Ritter et al., 2008, 2009).