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- Title
Dispersal of Spanish juniper Juniperus thurifera by birds and mammals in a fragmented landscape
- Authors
Telleria, J. L.; Santos, T.; Virgos, E.
- Abstract
Dispersal of Spanish juniper Juniperus thurifera was examined in a farming landscape of central Spain to study the effects of fragmentation on the dispersal effectiveness of the different dispersers, and the consequences for the plant. The study was conducted in two large forests (LF; 280 and 150 ha) representative of unfragmented conditions,and 18 small isolated fragments (0.1 to 3 ha) which were classified in two groups: 1) F1, forest remnants with both high juniper cover and cone production (N=5); and 2) F2, remnants in which fragmentation has caused a heavy reduction in junipers (N=13). Cone production, disperser abundances and quantity of dispersal by birds (Turdus thrushes)and mammals (carnivores, rabbits and sheep) were estimated throughout two study years. Dispersal by thrushes was measured in 3 types of tree representing a decreasing attraction focus to birds: Spanish junipers with cones (SJ1), Spanish junipers without cones (SJ2) and holm oaks (HO). Cone production greatly decreased from LF to F1 and F2 in both study years, affecting F2 dramatically. Thrush abundances were similar in LF and F1, but thrushes lacked or were very scarce in F2. Carnivores showed an even distribution throughout the whole area, but herbivores were relatively scarce in F2 fragments, especially rabbits, which were lacking in the fragments under 0,6 ha. Patterns of seed deposition around trees showed decreasing dispersal activity of thrushes from SJ1 (83.1% of the examined trees had seed-packets -thrush pellets) to SJ2 (53.6%) and HO (23.6%). Both distribution patterns and density of pellets were roughly similar in LF and F1, but pellets were only recorded in one (SJ1) out of 159 trees examined in F2, supporting thrushes behaved as specialist feeders and thus avoided the patches devoid of juniper cones. Average densities of pellets in LF reached 397.6 pellets/ha, surpassing at least 30 times the quantitative effectiveness (seed-packets/ha) of mammal dispersers. Juniper seeds werepr
- Subjects
FOREST ecology; FRAGMENTED landscapes
- Publication
Ecography, 1999, Vol 22, Issue 2, p193
- ISSN
0906-7590
- Publication type
Article