A global approach to analyze the extent of the newly detected Tropical Lowland Cloud Forest (TLCF) based on a large-scale analysis of fog frequency and epiphyte growth, with a special focus on South America

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Tropical cloud forests, with their extraordinary biodiversity particularly of epiphytic plants, are generally associated with mountainous regions, where they are referred to as Tropical Montane Cloud Forests. Our previous work in the Guianas now suggests that in basins and valleys of the Tropical Lowland Rain Forest (at elevations <500 m a.s.l.), which is normally characterized by a significantly lower epiphyte abundance and diversity, another type of epiphyte-rich cloud forest type exists, referred to as Tropical Lowland Cloud Forest (TLCF). We hypothesize that this new forest type occurs globally in all natural tropical lowland forests where a sufficient moisture supply allows the development of nocturnal canopy fog in terrain depressions. The main aim of the project is to test this hypothesis with a combination of satellite data, field measurements, climate model data and mechanistic modeling of epiphyte growth. First, potentially suitable regions are spatially delineated by means of global ancillary big data on topography, natural forest cover and fog occurrence. Particularly canopy fog occurrence requires reprocessing of the globally available MODIS data set with a newly developed subpixel fog detection scheme for tropical lowlands. The relationship between fog occurrence and the high abundance of canopy epiphytes in the TLCF is examined by applying and validating a newly developed carbon-exchange model for mosses, liverworts and filmy ferns (Hymenophyllaceae).