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1. Forest regrowth following farmland (agriculture and pasture) abandonment has been positively associated with a number of processes including the regulation of hydrological cycling, the enhancement of soil functioning and an increase in forest productivity and carbon (C) sequestration. Although these changes in eco-system functioning post-farmland abandonment have been observed in multiple locations and studies, the ecophysiological basis underpinning these patterns re-mains unclear. Here, we examine whether increased forest expansion following pastureland abandonment is associated with greater water-use efficiency (WUE) and legacies from previous land use in terms of nitrogen (N) availability., 2. We thus explored differences in leaf traits and N availability between recently es-tablished (post-1950) beech Fagus sylvatica (L.) forests on former pastureland and long-established beech forests (pre-1950). The investigated leaf traits were SLA, leaf N concentration (%N) and intrinsic WUE (iWUE, i.e. the ratio between photo-synthesis and stomatal conductance); as well, leaf and soil stable N isotope compo-sition (δ15N) and total %N were used to assess changes in N availability. Finally, we compared the correlation strength between the above-mentioned parameters and those associated with tree productivity (wood density and basal area increment, BAI) and the richness of ectomycorrhizal fungi (ECM) in these two forest types., 3. Recent forests had greater iWUE than long-established forests, which was associated more with lower SLA than leaf %N. Leaf and soil δ15N were more robust proxies than %N for detecting differences in N availability. Less negative leaf and soil δ15N values in recent versus long-established forests suggest, on the one hand, greater N avail-ability, probably due to higher historical N input originating from animal excreta on these former pasturelands, and, on the other hand, an increase in N loss pathways., 4. Our results point to greater correlations between leaf δ15N, tree iWUE and pro-ductivity in recent forests than in long-established forests, thereby suggesting a close link between C and N cycles. Our findings also highlight different N dynam-ics between the two forest types, with recent forests showing ‘leaky’ N cycling wherever lower N retention by trees and associated ECM fungi occurs as a legacy of previous land use., This study was supported by the projects: SPONFOREST (APCIN_ 2016_0174), NEWFORLAND (RTI2018-099397-B-C22 MCIU/AEI/ERDF, EU) and BEEMED (SGR913 Generalitat de Catalunya). Etal.was supported by the postdoctoral grant Juan de la Cierva-Formación from the Spanish Ministry of Economy, Industry and Competitiveness (grant no. FJCI-2015-26848). T

Given the worldwide plans for extensive tree planting, we urgently need to understand how and where implementation will contribute to goals such as those for carbon sequestration. We used a long-term, large-scale native reforestation project in the Scottish Highlands to assess the response of carbon storage and other ecosystem functions to reforestation and grazing exclusion. We measured aboveground carbon, topsoil carbon, topsoil nitrogen, decomposition rates, soil invertebrate feeding activity, tree regeneration, and ground-layer and moss height at 14 sites that are in the early stages of reforestation and fenced to exclude grazing. Reforestation areas were compared to unforested and mature forest areas that are both grazed and ungrazed, using 10 × 10 m plots. Aboveground carbon in the reforestation plots (1.4 kg/m 2 [95% CI: 0.6, 2.6], average age 20 years since reforestation) was c. 8% of the mature forest plots (17.1 kg/m 2 [13.1, 21.8]). Topsoil carbon was lower in the reforestation plots (18.78 kg/m 2 [11.79, 25.78]) than in the unforested (29.82 kg/m 2 [24.34, 35.29]) or mature forest (31.39 kg/m 2 [22.91, 39.88]) plots. Responses of other functions to the reforestation and grazing interventions varied. Our results suggest that reforestation may trigger carbon loss from areas with high initial soil carbon even with low disturbance establishment, at least in the short term. Our work emphasizes where we lack knowledge: on the potential for long-term re-accumulation of soil carbon under semi-natural native reforestation, soil carbon sequestration in the deeper soil layers, and the response of soil carbon to natural regeneration.

Globally, there is increasing interest in tree planting, leading to many country-level commitments to reforestation. In the UK, current commitments would achieve 17% forest cover by 2050, with the highest rates of forest expansion expected in Scotland. Forest expansion with native trees is expected to increase biodiversity, particularly woodland specialist species, and associated ecosystem services. Despite this, data on biodiversity changes over the early stages of reforestation are sparse, particularly for upland areas in Scotland where opportunities for forest expansion are greatest. We collected data on the response of plants, carabid beetles and birds to native reforestation and grazing exclusion, using sites reforested over the last 30 years in the Scottish Highlands. Biodiversity in ungrazed, reforested sites was compared to unforested controls and mature native forest, both grazed and ungrazed. Mean bird species richness in reforested plots (4.4 [95% CI: 3.2, 5.9]) was higher than in unforested plots (0.8 [0.5, 1.3]), but lower than in mature forest plots (7.0 [5.4, 8.3]). In contrast, there was no systematic difference in plant or carabid beetle species richness in reforested, unforested or mature forest plots, or between grazed and ungrazed plots for the species richness of any groups. Woodland specialist bird and plant species were found in the reforested plots, and richness of woodland specialist bird species was predicted to reach levels in mature forest c. 36 years after reforestation. Species assemblages differed across habitat categories. For birds and plants, species assemblages in reforested sites were intermediate to unforested and mature sites. For carabid beetles, the assemblages in mature and reforested sites were comparable and differed from unforested sites. Grazing did not strongly influence species assemblages. Policy implications. We show that woodland specialists colonise reforested sites and species assemblages transition towards those found in the target habitat within the first 30 years of reforestation with native species. Native forest should be prioritised in Scotland's future forest expansion targets, given that mature native forest is scarce and fragmented in the Scottish Highlands and that the ultimate gain from native forest expansion may accrue over long time-scales.

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. 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., Funding was provided by the Spanish Ministries for Education (FPU-MEC grant) and Innovation and Science (projects: CGL2010-16388/BOS, Consolider-Montes/CSD2008_00040; VULGLO/CGL2010-22180-C03-03 and CALCOFIS/CGL2009-13013), and by the Community of Madrid project REMEDINAL 2 (CM-S2009/AMB-1783).