Giant Rosette Plants

Acaulescent Plants

The most typical life form of alpine tropical regions are the giant-rosette plants of the genera Lobelia (Lobeliaceae) and Senecio (Asteraceae) in Africa, Espele-tia (Asteraceae) in South America and Argyroxiphium (Asteraceae) in Hawai'i (Fig. 12.5). They may reach heights of several meters and have developed a number of morphological and anatomical features adapting them to the diurnal type of climate in their habitat. The tallest plant of Senecio johnstonii ssp. cottonii actually measured by...

Ecophysiological Responses to Drought

5.1 Drought in Moist Tropical Forests Seasonality of rainfall (Sect. 3.1) can lead to the formation of tree rings in wet tropical forests (Worbes 1999 D nisch et al. 2003). Seasonal drought may occur regularly in these moist forests and not only in dry tropical forests. In Central and South America it can be enforced by southern oscillation or El Ni o events (Engelbrecht et al. 2002). After extreme dry periods tropical rain forests may even be threatened by fire (van Nieuwstadt and Sheil 2005,...

Drought in Dry Tropical Forests

From wet to dry species in the tropics face increasing problems of water availability (Holbrook and Franco 2005). The dominating ecophysiological stress parameters in dry tropical forests are strong seasonal drought (H2O) and high irradiance (hv, see Chapter 4 for a detailed discussion) with strong interactions between them and with other environmental parameters, i.e. 1. h v T Absorption of radiation by leaves leads to heating. 2. H2O h v Heating and drying of the atmosphere, increases the...