Colonization of Abandoned Land by Juniperus thurifera Is Mediated by the Interaction of a Diverse Dispersal Assemblage and Environmental Heterogeneity

Abstract

Land abandonment is one of the most powerful global change drivers in developed countries where recent rural exodus has been the norm. Abandonment of traditional land use practices has permitted the colonization of these areas by shrub and tree species. For fleshy fruited species the colonization of new areas is determined by the dispersal assemblage composition and abundance. In this study we showed how the relative contribution to the dispersal process by each animal species is modulated by the environmental heterogeneity and ecosystem structure. This complex interaction caused differential patterns on the seed dispersal in both, landscape patches in which the process of colonization is acting nowadays and mature woodlands of Juniperus thurifera, a relict tree distributed in the western Mediterranean Basin. Thrushes (Turdus spp) and carnivores (red fox and stone marten) dispersed a high amount of seeds while rabbits and sheeps only a tiny fraction. Thrushes dispersed a significant amount of seeds in new colonization areas, however they were limited by the presence of high perches with big crop size. While carnivores dispersed seeds to all studied habitats, even in those patches where no trees of J. thurifera were present, turning out to be critical for primary colonization. The presence of Pinus and Quercus was related to a reduced consumption of J. thurifera seeds while the presence of fleshy fruited shrubs was related with higher content of J. thurifera seeds in dispersers’ faeces. Therefore environmental heterogeneity and ecosystem structure had a great influence on dispersers feeding behaviour, and should be considered in order to accurately describe the role of seed dispersal in ecological process, such as regeneration and colonization. J. thurifera expansion is not seed limited thanks to its diverse dispersal community, hence the conservation of all dispersers in an ecosystem enhance ecosystems services and resilience.

Geographic consistency in the seed dispersal patterns of Taxus baccata L. in the Iberian Peninsula

“…Although a large proportion of the seeds lands underneath conspecifics, the fraction that escapes from the neighborhood of T. baccata trees is crucial for subsequent stages of the species' population dynamics (González- Schupp & Jordano, 2011). As the main driver of seed flow, frugivorous birds play a pivotal role for yew populations, however carnivorous mammals should not be neglected since they contribute to the recolonization process through long distance dispersal (Escribano-Avila et al, 2012). Conservation and management practices should focus on maintaining a frugivore assemblage as diverse as possible to allow for complementary seed dispersal (García & Martínez, 2012;Escribano-Avila et al, 2014), thus increasing the chance for a seed to reach favourable conditions and acus preferentially forage around the focal trees, sometimes in big flocks (T. iliacus), and fly short distances towards the neighbouring microhabitats (Martínez et al, 2008), thus most likely dispersing the seeds within forest patches.…”

“…Despite their potential to disperse the seeds over long distances (Jordano et al, 2007;Matías et al, 2009), their role as efficient seed dispersers remain unclear. Indeed, Peredo et al (2013) found that they deposited a large fraction of the seeds into unsuitable microhabitats for germination and seedling establisment, such as latrines in the case of badgers, a microsite where seeds are probably faced to overcrowding and recurrent disturbance (but see Escribano-Avila et al, 2012).…”

“…Additionally, carnivorous mammals have been found to disperse a small fraction of seeds and contribute rather differently, as they frequently defecate the seeds in open areas such as trails or rocks, but generating very big clumps in faeces and latrines (Guitián & Munilla, 2010;Peredo et al, 2013). Although germination rate and seedling survival after mammal deposition are likely to be low, mammal seed dispersal may still play a role in re-colonizing deforested and distant areas (Jordano et al, 2007;Escribano-Avila et al, 2012;Peredo et al, 2013).…”

Colonization in Mediterranean old‐fields: the role of dispersal and plant–plant interactions

“…Endozoochorous dispersal in junipers is carried out by different groups of birds and carnivore mammals that play complementary roles and make dispersal highly effective (Escribano‐Ávila et al. , ), thereby promoting the early colonization of abandoned fields. In our study system, birds are responsible for dispersal services at the local scale (tens to a few hundred meters; Breitbach et al.…”

“…), whereas carnivores such as red fox ( Vulpes vulpes ) or stone marten ( Martes foina ) favour long‐distance seed dispersal, which can frequently exceed 1–2 km (Escribano‐Ávila et al. ). In contrast, wind‐dispersed pine seeds reach shorter distances from the mother plant (around 30 m on average; Ribbens et al.…”