Changes in the fruiting landscape relax restrictions on endozoochorous tree dispersal into deforested lands

Abstract

Question: Passive forest restoration is based on the natural recovery of degraded habitats. However, tree recruitment is frequently hampered in deforested lands. Tree seed dispersal is scarce and spatially constrained, confining the potential of forest regeneration to a narrow band surrounding forest remnants. Understanding how landscape configuration can favour endozoochorous seed dispersal into deforested lands is thus crucial to recover forest extent and the concomitant ecosystem services. Can distance restrictions on seed dispersal be modified as a result of temporal variability of fruit-frugivore systems?Location: Deforested montane pastures surrounding fragments of secondary temperate forest, Cantabrian Range, Spain.Methods: For 2 yr, we evaluated the patterns of fruit production, frugivorous bird movement and tree seed dispersal through the landscape. Seed dispersal in deforested sampling stations was related to their distance to forest cover and the amount of forest cover in their surroundings. Results:The large-scale spatial distribution of fruits varied strongly between years, with relatively higher fruit production in isolated trees within pastures in the second year, when birds were more frequently observed perching on isolated trees. In both years, few seeds were dispersed into deforested areas, and those dispersed occurred close to forest cover. Nevertheless, seed arrival at longer distances increased during the second year. When more fruits were produced within the pastures, birds more often overcame their reluctance to leave the forest, and this change in frugivore foraging patterns cascaded into the spatial patterns of seed dispersal.Conclusions: By influencing frugivore activity, temporal dynamism in fruiting landscapes can relax the restriction on tree seed dispersal into deforested areas. Landscape biological dynamism should be taken into account in order to manage rewilding in European temperate forests.

Disentangling habitat use by frugivorous birds: Constant interactive effects of forest cover and fruit availability

“…Nevertheless, this temporal dynamism in the large-scale distribution of fruits would probably be affecting the relative strength of the respective influences of habitat cover and food availability, which actually varied across years (Table 3; Appendix C: Table 1). These variations in strength would agree with the temporal variability highlighted in previous studies in the same system, affecting other aspects of these plant-frugivore interactions, from fruit consumption to seed dispersal (Herrera et al 2011;García et al 2013;Martínez & García 2014;Martínez et al 2014). …”

“…Such a consistent pattern of interactive effects occurred even when the abundance and the spatial distribution of fruits varied strongly between years over the forest cover (Appendix D: Fig. 1; see García et al 2013;Martínez & García 2014 for variations in fruit spatial distribution). Nevertheless, this temporal dynamism in the large-scale distribution of fruits would probably be affecting the relative strength of the respective influences of habitat cover and food availability, which actually varied across years (Table 3; Appendix C: Table 1).…”

“…For the better management of spatial information, the plot was subdivided into 440 20 × 20 m cells. Previous studies have proven that the size of the study plot and cells are appropriate in terms of extent and grain, respectively, for studying variability in habitat cover and fruit abundance, with cell size representing a relevant scale for bird habitat use and heterogeneity in seed rain patterns (García & Martínez 2012;García et al 2013;Martínez & García 2014). The study was carried out over four consecutive years: the autumn-winter seasons of 2008-09, 2009-10, 2010-11 and 2011-12 (hereafter, respectively 2008, 2009, 2010 and 2011).…”

“…Previous studies in the same system have described seed rain patterns and their variability between years and through the landscape (Herrera, Morales, & García 2011;García et al 2013;García & Martínez 2012;Martínez & García 2014). Nevertheless, we still lack a proper understanding of the ecological mechanisms (i.e.…”

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

“…Turdus spp., Jordano, 1993;Tellería et al, 2014). Thus, the yearly patterns of yew seed dispersal are expected to change, as conditioned by both community-whole fruit availability and frugivore abundance (see Martínez & García, 2015a, for other tree species with similar dispersal syndrome).…”