Disentangling factors controlling fruit and seed removal by rodents in temperate forests

Fleshy fruits fall on to the ground together with cleaned seeds previously ingested by primary dispersers, offering a wide range of fruits and seeds to the ground foragers. Although nutritional properties strongly differ between fruits and seeds, this different seed presentation (cleaned seeds versus seeds within the pulp) has not been addressed in seed removal studies. This study reports on the removal of fruits versus their seeds in five fleshy-fruited species in a temperate forest. We found that rodents removed most of the seeds and partially consumed most of the fruits, preferring seeds to fruits. Rodents bit the fruits to extract the seeds, leaving most of the pulp. We found a preference ranking for the seeds (Sorbus aucuparia>Ilex aquifolium>Sorbus aria>Rosa canina>Crataegus monogyna) but no preferences were found for the fruits, probably due to their similarities in pulp constituents. Seed and fruit choice were affected by chemical and physical properties and not by their size. The presence of alternative and preferred seeds (nuts) delayed the encounter of the fruits and seeds and diminished their removal rates. We found that higher rodent abundance is not necessarily associated with higher removal rates of fleshy fruits. Rodent abundance, fruit size and seed size are minor factors in the removal of fleshy fruits and their seeds. This study underlines that scatter-hoarding rodents are important removers of fleshy fruits and their seeds, producing a differential seed removal depending on the seed presentation (with or without pulp), the nutritional properties of the seeds (but not of the fruits) and the presence of alternative food

Influence of climate change on the flowering of temperate fruit trees

It is well known that winter chilling is necessary for the flowering of temperate trees. The chilling requirement is a criterion for choosing a species or variety at a given location. Also chemistry products can be used for reducing the chilling-hours needs but make our production more expensive. This study first analysed the observed values of chilling hours for some representative agricultural locations in Spain for the last three decades and their projected changes under climate change scenarios. Usually the chilling is measured and calculated as chilling-hours, and different methods have been used to calculate them (e.g. Richarson et al., 1974 among others) according to the species considered. For our objective North Carolina method (Shaltout and Unrath, 1983) was applied for apples, Utah method (Richardson et al. 1974) for peach and grapevine and the approach used by De Melo-Abreu et al. (2004) for olive trees. The influence of climate change in temperate trees was studied by calculating projections of chilling-hours with climate data from Regional Climate Models (RCMs) at high resolution (25 km) from the European Project ENSEMBLES (http://www.ensembles-eu.org/). These projections will allow for analysing the modelled variations of chill-hours between 2nd half of 20C and 1st half of 21C at the study locations.