Myrcianthes

Leaf responses to irrigation of the endemic fog-oasis tree Myrcianthes ferreyrae: Can a fog-specialist benefit from regular watering?

David A. Ramírez 1,2*, Luis Balaguer 3, Rosa Mancilla 4, Virginia González 1, Daniel Coaguila 4,5, Carmelo Talavera 4, Luis Villegas 4, Aldo Ortega 4, Percy Jiménez 4, José M. Moreno1


1 Departamento de Ciencias Ambientales, Universidad de Castilla – LaMancha, 45071 Toledo, Spain
2 Departamento de Biología, Universidad Nacional Agraria La Molina, Lima, Perú
3 Departamento de Biología Vegetal I, Universidad Complutense de Madrid, E-28040 Madrid, Spain
4 Laboratorio de Ecología, Departamento Académico de Biología, Universidad de San Agustín, Arequipa, Perú
5 Departamento de Ecología, Universidad de Alicante, 99-E-03080 Alicante, Spain



*Corresponding author: DavidAntonio.Ramirez@uclm.es, Phone: +34 925 268 800 ext. 5470, fax: +34 925 268 840



Running title: Responses to watering of a fog-oasis tree

Abstract
Myrcianthes ferreyrae is an endemic species with a scarce number of individuals located only in fog-oases (named “lomas”) along the Peruvian Desert in the South of Perú, where fogs are the main source of water inthis hyperarid region. After centuries of severe deforestation, reforestation this native species was carried out in the “Atiquipa Lomas” (Arequipa, Perú). In 5 slopes, five 2-year-old seedlings were monthly irrigated with water trapped by raschel-mesh fog collectors that supplemented natural rainfall with 0, 20, 40, 60 and 80 mm month-1 from February to August 2008. Plant growth rate was estimatedfrom the variation of shoot basal diameter and maximum height, and both were highly correlated with total biomass. We measured in 4 leaves of each seedling: leaf mass area (LMA), leaf carbon isotope composition (δ13C), nitrogen per leaf area, leaf total carbon and stomatal density. According with the plant growth response, only the LMA and δ13C were higher in irrigated than control plants but withno further response to increasing water supply. This threshold response suggests an on-off strategy fitted to exploit pulses of fog water availability. The absence of a gradual response, however, is in consonance with the low phenotypic plasticity expected in plants from stressful environments


Key Words: Peruvian Desert, δ13C, fog, leaf mass area, Lomas, Myrcianthes ferreyraeIntroduction
“Lomas” ecosystems are fog-oases into of the Peruvian and Atacama deserts which form an hyperarid belt close to the Pacific Ocean coast from North of Perú to North of Chile (7-28ºS latitude) (Dillon et al., 2009). These deserts are considered as the driest of the planet (Rundel et al., 1991), where Cereceda et al. (2008) using 30 years of meteorological records calculated 0.8 mm of theaverage yearly precipitation in the Atacama Desert. Similar to other hyperarid areas (Henschel and Seely, 2008) the fog from the ocean is the most important water resource for the “lomas” (Cereceda et al., 1999). Thus, trees intercept the fog with their aerial architecture and throughfall and stemflow percolate into the soil and recharges the groundwater (Dawson, 1998; Edner et al., 2011). Fogcollectors (Schemenauer et al., 1987) have been set up and tested in these deserts (Cereceda et al., 2008; Larrain et al., 2002; Schemenauer and Cereceda, 1993; Sotomayor and Jiménez, 2008; Westbeld et al., 2009). The amount of water trapped by these collectors in other hyperarid environments reaches maxima of 1.0, 5.7 and 7.0 mm day-1 reported for the Namib Desert (Henschel and Seely, 2008), the WestCoast of South Africa (Olivier, 2002) and the Atacama Desert (Cereceda et al., 2008), respectively.

In the “lomas” ecosystems reforestation activities have been carried out with the aim to restore endemic and economic tree species which have been reduced by old cutting practices (Suasnabar et al., 2004). Unfortunately, there is little information about reforestations using fog water collected...