Spanish Juniper Juniperus Thurifera Research Articles

Diverse guilds provide complementary dispersal services in a woodland expansion process after land abandonment

Summary Land abandonment due to increasing depopulation of rural areas is an ongoing trend in developed countries worldwide. Abandoned lands represent an opportunity for ecosystem recovery, an urgent need for biodiversity conservation. Seed dispersal services provided by animals are a key feature for this process. Different dispersers may differentially contribute to plant recruitment under different ecological conditions, leading to complementary dispersal services. We studied the dispersal services, quantified as the contribution to plant recruitment, provided by the main dispersal guilds of Spanish juniper Juniperus thurifera L.: small‐to‐medium‐sized strongly frugivorous birds (thrushes) and medium‐to‐large‐sized carnivorous mammals (red fox and stone marten). To do this, we studied seed fate from seed dispersal to seedling survival during 2 years and estimated seed dispersal effectiveness (seedlings recruited per m2) in two ecological contexts derived from ecosystem recovery after a historical period of degradation: remnant woodlands and old fields. Results showed a clear shift in the contribution to plant recruitment between these guilds, resulting in complementary and non‐redundant dispersal services. Thrushes were the main contributors to plant recruitment in woodlands (73%), leading to population growth but with a reduced impact on the colonization of old fields where carnivores contributed to 80% of recruitment (42% red fox, 38% stone marten). The dispersal complementarity observed for thrushes and carnivores is a consequence of their functional diversity, mainly driven by their differences in feeding and movement behaviour. Synthesis and applications. The combination of short‐distance, strongly frugivorous dispersers (e.g. passerine birds) together with big generalist frugivores with long‐distance movements (e.g. carnivorous mammals) maintained (i) effective seed dispersal services in remnant woodlands and (ii) the connectivity between patches promoting old fields colonization and woodland expansion. Thus, it is in heterogeneous landscape mosaics ecosystems (e.g. agro‐environments) where functionally diverse disperser communities play a key role in ecosystem recovery. By performing effective dispersal services across an array of habitat types, functionally diverse disperser communities assist natural restoration of human‐impacted ecosystems all over the world. Thus, dispersal communities provide an important ecosystem service that may replace costly human‐mediated restoration projects.

Species abundance and migratory status affects large-scale fruit tracking in thrushes (Turdus spp.)

The mutualistic interactions between fruit-producing plants and seed-dispersing birds may be disrupted by the difficulties involved in tracking fruit resources, which are often patchily distributed in space and time. As a consequence, the strength of this interaction will rely on the ability of birds to distribute numbers according to the spatiotemporal patterning of the resource. This paper tests if wintering thrushes (Turdus) track inter-winter and inter-site changes of cone abundance in an area that encompasses the main range of the Spanish Juniper Juniperus thurifera in the Iberian highlands. We test whether the regional abundance and migratory status of birds affect this fruit-tracking process. Analyses were approached by using the habitat matching rule, a null model applied to explore the effect of spatiotemporal change of resources on bird distribution. All species followed inter-winter food variation over the study area but under-matched the changes. The strength of this bird–plant interaction increased with the regional abundance of individual species. When thrushes were analyzed according to their migratory status, migratory species (Turdus pilaris, T. iliacus, and T. philomelos) tracked the resource better than sedentary ones (T. viscivorus and T. merula). This suggests that in a time of rapid environmental change any reduction of vagrant and abundant migratory thrushes could weaken the strength of this bird–plant interaction.

Conservation Opportunities in Spanish JuniperJuniperus thuriferaWoodlands: The Case of Migratory ThrushesTurdusspp.

Conservation opportunities in Spanish juniper Juniperus thurifera woodlands: the case of migratory thrushes Turdus spp.Spanish juniper Juniperus thurifera woodlands are the core habitat of several sites included in the Nature 2000 Network and the wintering ground of many European thrushes Turdus spp. These birds have a major ecological role as seed dispersers and are increasingly taken into account in the design of strategies aimed to conserve or restore plant communities. Socio-economic changes in rural Spain have reduced traditional sheep grazing in juniper woodlands, which are now increasingly used for wood production. This has brought the opportunity to improve their carrying capacity for migratory thrushes. Here we explore the spatio-temporal patterning of fleshy cone production and the way birds track this resource. We also investigate whether fleshy cone availability constrains bird numbers. The results show sharp losses of cones during the ripening period, inter-site and inter-winter changes in cone production and the tracking of ripe cones by birds. Mean availability of ripe cones in poorly productive patches was insufficient to maintain thrushes in mid January and highly productive patches offered resources to maintain birds for around 12 days. This suggests an insufficiency of food in the woodlands to permit thrushes to complete the winter and to begin their return northward migration in March. These results are used to suggest some guidelines for improving the carrying capacity of these woodlands for migratory thrushes.

Dispersal of Spanish juniper Juniperus thurifera by birds and mammals in a fragmented landscape

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 ‐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 three types of trees representing a decreasing attraction focus to birds: Spanish junipers with cones (SJI). 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‐1, surpassing at least 30 times the quantitative effectiveness (seed‐packets ha‐1) of mammal dispersers. Juniper seeds were present but very scarce in the mammal faeces collected in both fragments F1 and F2. Overall, the quantitative effectiveness of carnivores was nearly 4 times lower in the fragments than in LF, and that of herbivores 11 times lower. This result is consistent with the lower availability of juniper cones in the fragments and. together the distribution of mammal abundances, fits the prediction that mammals (except rabbits) moved among landscape patches according to the total availability of food supplies.Overall, results showed that dispersal of Spanish juniper in fragments F2 is seriously impaired by the loss of their main dispersers (thrushes), and that recruitment became dependent upon mammal dispersers with a low quantitative effectiveness, namely carnivores and sheep.

Influence of forest fragmentation on seed consumption and dispersal of Spanish juniper Juniperus thurifera

We examined the effects of fragmentation on Spanish juniper Juniperus thurifera in central Spain by comparing eight small forest fragments (SF: 0·2–16 ha) with two large forests (LF:150 and 270 ha). Wood mice Apodemus sylvaticus, the only rodent seed eaters, were 8·9 times more dense in SF, whereas thrushes Turdus spp., the main avian seed dispersers, were 4·6 times more abundant in LF. Finches (seed eaters) were scarce in both forest groups. Mean fruit abundance was significantly higher in LF. Seed consumption was mainly by mice in SF and by finches in LF. Thrush pellets with intact seeds, seedling abundance and the proportion of trees with nearby seedlings, were all higher in LF. This evidence points to a decrease in the dispersal efficiency of Spanish juniper in SF. We suggest that the processes leading to reduced dispersal ability might be inherent to fragmentation and represent a threat for the survival of fruit-bearing plants in patchy environments.