Biology subjects

Vaz, P. G.

Publications and source records attributed to Vaz, P. G..

11 recordsLinked to original sources

bioRxiv2026

Road proximity differentially shapes rodent-mediated seed dispersal frequency and distance

By concentrating rodents along verges, roads can reshape rodent-mediated seed dispersal, yet empirical tests remain scarce. We conducted a two-year field experiment in Mediterranean oak woodlands in southern Portugal to test how seed dispersal varies with distance from roads across road type (paved vs. unpaved) and road-forest context (edge vs. non-edge). We tracked labeled holm oak acorns, recording dispersal distances and the number of dispersal events. The two metrics responded differently to road distance. Dispersal distances changed little with distance from roads in non-edge contexts but increased in edge road-forest contexts (2x longer at 400 m than at 10 m) and showed a year x distance-to-road interaction, with longer dispersal distances farther from roads in the second year (a poor mast year). Dispersal distances were also longer when acorns were deposited under shrubs and in areas of higher tree density, and decreased with greater natural acorn availability. In contrast, the number of dispersal events declined with distance from roads (30% more events at 10 m than at 400 m) and was higher along unpaved than paved roads (39% more events). Dispersal frequency also increased in the poor mast year and with shrub cover. No acorns crossed the road. Thus, road verges can concentrate rodent seed handling but do not increase dispersal distances near roads nor provide cross-road seed connectivity; instead, dispersal outcomes depend on edge context, road type, and microhabitat structure. Management that retains structural cover at verges and the adjacent forest edge (e.g., shrub patches and non-uniform clearing) can harness verge-associated activity to increase acorn deposition in sheltered microsites and promote regeneration farther into forest interiors in roaded landscapes.

ecology↗

bioRxiv2025

Resprouting sustains cork oak seedlings while recent grazing limits resprouting and survival

Regeneration failure is a bottleneck in Mediterranean oak woodlands. Cattle can hinder or promote recruitment, depending on grazing location, timing and intensity. Herbivory theory predicts that repeated defoliation and trampling deplete seedling reserves, whereas resprouting can extend survival; yet field studies rarely separate intensity from recency or combine long-run grazing records with individual fates and microhabitat/climate context. We test how management-driven heterogeneity shapes cork oak seedling survival and resprouting by combining 12 years of paddock-level grazing records with individual tracking of 8431 seedlings across 24 paddocks. Bayesian mixed-effects survival models related seedling lifespan to grazing history x pressure (moderate [≤]150; high >150 LSU ha-1 days yr-1) and to key covariates, including seedling height, resprouting status, shrub distance, cattle dung counts (as a proxy of very recent grazing), and 1-month SPEI (as recent water balance). Bayesianlogistic mixed models were then used to relate resprouting probability to grazing treatments. Survival was lower in grazed than ungrazed paddocks and declined along management gradients: median lifespan fell from 460 (moderate grazing) to 256 days (high), and from 460 (old grazing; two-year absence) to 199 days (recent). A two-year cattle absence increased survival under moderate pressure but was insufficient where pressure was high, indicating legacy effects and that recovery windows must scale with pressure. Resprouting dominated persistence: resprouters lived >5x longer than non-resprouters (2351 vs 460 days). Taller seedlings lived longer, and shrub proximity conferred a modest benefit. Climate modulated outcomes: wetter recent periods (higher SPEI) markedly boosted survival. Cattle reduced the odds of resprouting, with the strongest penalty under recent use. By disentangling grazing intensity from recency and linking both to seedling survival and resprouting, we show why recruitment falters under continuous, heavy grazing and when it can recover. Because drought intensifies cattle impacts, managers should combine moderate stocking rates with multi-year rest periods to rebuild oak bud banks and below-ground reserves; a two-year hiatus can help under moderate pressure but appears insufficient where pressure is high. Aligning rotational plans with drought outlooks and tracking simple field cues (seedling height, recent resprouting) offers a practical path to reconcile production with regeneration in Mediterranean wood-pastures. HighlightsO_LITwelve years of grazing records linked to 8431 cork oak seedling fates C_LIO_LIRecent grazing reduced survival and resprouting versus a two-year cattle absence C_LIO_LIHigh grazing shortened lifespan; two-year rest helped only under moderate pressure C_LIO_LIResprouting was the strongest survival correlate; resprouters lived over 5x longer C_LIO_LIWetter short-term water balance increased cork oak seedling longevity C_LI

ecology↗

bioRxiv2025

Carnivore-mediated seed crossings are more likely on roadkill hotspots

Roadkill hotspots concentrate animal movement and mortality, but whether they also interfere with animal-mediated seed dispersal--a conservation-relevant process underpinning plant regeneration and landscape connectivity--remains unknown. In Mediterranean oak woodlands of southern Portugal, we used seed mimics to test how road type (paved vs. unpaved) and road-forest context (edge vs. non-edge) shape carnivore-mediated seed crossings, and whether crossings coincide with roadkill hotspots detected by kernel density analysis. Bayesian logistic models indicated that seed-crossing probability was about twice as high on unpaved as on paved roads (predicted means 0.28 vs. 0.14), with weaker evidence for a negative edge effect. Crossing probability also tended to increase with carnivore abundance and distance to streams, and decrease with rodent density, albeit with some uncertainty. Crucially, paved sections intersecting roadkill hotspots showed nearly threefold higher predicted crossing probabilities than non-hotspot sections (0.51 vs. 0.18). These results yield clear conservation implications: prioritize paved segments that overlap carnivore roadkill hotspots. Implement precision measures--short-segment speed management, directional fencing that funnels animals to existing culverts/underpasses, and verge management that removes carcasses and limits small-mammal/scavenging attractants--to cut mortality while maintaining seed-mediated connectivity. A light, repeatable monitor-act-reassess workflow (hotspot mapping + seed-mimic trials + camera checks) enables rapid deployment and evaluation, and is transferable to other human-dominated forest mosaics. Hotspot-guided mitigation offers a pragmatic path to reconcile mobility infrastructure with living connectivity.

ecology↗

bioRxiv2025

Roads shape seed dispersal by rodents and carnivores at forest edges

The influence of road networks on seed dispersal remains poorly understood. We conducted a field experiment in Mediterranean oak woodlands of southern Portugal to assess how road type (paved vs. unpaved) and road-forest context (edge vs. non-edge) shape seed dispersal by rodents and carnivores. Using labeled acorns and seed mimics, we tracked dispersal distances, number of dispersals, road crossings, and dispersal directions. Rodents dispersed seeds farther in forest edges and along paved roadsides, predominantly moving them parallel to roads, but rarely across--although crossings were more frequent on unpaved roads. In contrast, carnivores mediated long-distance dispersal, primarily perpendicular to roads, and although seed road crossings were rare, carnivore-dispersed seeds crossed roads--especially unpaved ones--nine times more frequently than rodent-dispersed seeds. Shrub cover increased rodent-mediated dispersal events, heavier acorns traveled farther, and water patches decreased carnivore-mediated dispersal events near roads. These findings highlight the dual role of roads as barriers and of roadsides as corridors for seed dispersal, with implications for forest regeneration and landscape connectivity. Roadside management should prioritize moderate shrub cover along paved roads to support rodent dispersal while balancing ecological benefits with potential trade-offs. Unpaved roads, in turn, should be managed as functional corridors for carnivores, enhancing connectivity between fragmented forests. By integrating species-specific dispersal processes into road planning, landscapes can be designed to minimize road barrier effects while promoting natural regeneration in human-modified forests.

ecology↗

bioRxiv2024

Relative fire-proneness of land cover types in the Brazilian Atlantic Forest

Fires are increasingly affecting tropical biomes, where landscape-fire interactions remain understudied. We investigate the fire-proneness--the likelihood of a land use or land cover (LULC) type burning more or less than expected based on availability--in the Brazilian Atlantic Forest (AF). This biodiversity hotspot is increasingly affected by fires due to human activities and climate change. Using a selection ratio-based approach, we analyzed fire-LULC interactions in 40,128 fires over a 35-year period (1987-2022) across various ecoregions in the AF. Our findings revealed that secondary forests, forest areas that have regrown after major disturbances, burned 61% more than expected by chance, whereas old-growth forests, native forests that have developed over very long periods, burned 57% less than expected, highlighting a nearly inverse relationship in their fire-proneness. Interestingly, our data indicate that pastures in the AF are less prone to fire than expected, despite being considered among the land uses that burn the most in Brazil. Other LULCs showed variable fire-proneness, with some differences between ecoregions. Over time, the fire-proneness of secondary forests decreased, likely due to forest aging and changes in land management practices. We emphasize the necessity for tailored fire management strategies that address the unique vulnerabilities of secondary forests, particularly in the context of ongoing restoration efforts aimed at increasing native forests. Effective measures, including the implementation of fire-smart management practices and enhancing the perceived value of secondary forests among local communities, are crucial for mitigating fire risks. Integrating these strategies with incentive-based approaches can bolster fire prevention, ensuring the long-term success of restoration programs. Our study provides a framework for understanding fire-landscape dynamics in tropical forests and offers actionable insights for practitioners working to safeguard these biomes from the escalating threat of wildfires. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/604452v2_ufig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@612bc4org.highwire.dtl.DTLVardef@1806cc0org.highwire.dtl.DTLVardef@63c47corg.highwire.dtl.DTLVardef@1f8b252_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIEvaluation of land cover fire-proneness in a tropical biome using a selection ratio. C_LIO_LISecondary forests burned 61% more; old-growth forests 57% less than expected by chance. C_LIO_LIPastures in the Atlantic Forest seem less fire-prone than expected, despite frequent burns. C_LIO_LIFire-proneness of secondary forests has generally been decreasing over time. C_LIO_LITailored fire management is essential to protect secondary forests in restoration efforts. C_LI

ecology↗

bioRxiv2024

Meta-analysis of livestock effects on tree regeneration in oak agroforestry systems

Livestock grazing occupies over a quarter of terrestrial land and is prevalent to agroforestry ecosystems, potentially affecting the survival, growth, and density of trees early developmental stages, such as seeds, seedlings, and saplings. To address the effects of livestock on tree recruitment in the face of ongoing debates about their impacts, we conducted a 33-year meta-analysis in Quercus-dominated agroforestry systems. Our analysis revealed a consistently negative effect of livestock on oak acorns, seedlings, and saplings. Significantly, livestock body size influenced oak regeneration, with small-sized livestock, notably sheep and goats, having a more pronounced negative impact compared to mixed-size systems, mainly involving cattle and sheep. The effects of small-sized livestock were markedly detrimental on acorn survival and seedling/sapling density, although no studies eligible for meta-analysis examined large livestock impacts on acorns. Overall, mixed-size livestock systems, often involving cattle and sheep, lessen the negative effects. Our findings indicate that the body size and foraging behaviors of livestock should be considered for the ecological sustainability of the tree component in agroforestry systems. While protective measures have long been integral to well-managed agroforestry systems, our results underscore the importance of integrating diverse livestock sizes and applying specific protective strategies, particularly for acorns and saplings, to further refine these practices. Future research should expand to underrepresented regions and livestock types to refine global agroforestry management practices. HighlightsO_LILivestock reduces oak tree regeneration at acorn, seedling, and sapling stages. C_LIO_LISmall livestock effect more negative, especially acorn survival and young oak density. C_LIO_LIMixed-size livestock agroforestry systems reduce harm more than small single-size ones. C_LIO_LIWe challenge perceptions that replacing cattle with sheep is necessarily less harmful. C_LIO_LIWe advocate for diverse livestock sizes in Quercus-dominated agroforestry systems. C_LI

ecology↗

bioRxiv2023

Cattle grazing alters how cork oak crop failure leads to faster and farther rodent-mediated acorn dispersal

Masting, the synchronized production of variable quantities of seeds, occurs in many grazed systems and can be interspersed with years of extreme crop failure, whose frequency and unpredictability are increasing with climate change. Yet, the combined impact of crop failure and grazing on seed dispersal and seed-to-seedling transition remains poorly understood. To address this concern, we investigated rodent-mediated cork-oak (Quercus suber) acorn predation, dispersal, and seedling emergence in cattle grazed and non-grazed areas in central Portugal during years with contrasting masting seasons. We found that extreme crop failure led to six times longer and faster acorn dispersal, with 83% more dispersal events than during a year of reproductive success. The percentage of predated acorns also increased by 84%. However, the higher acorn predation was offset by a 2.4-fold higher percentage of unpredated dispersed acorns recruiting into seedlings. Both years ended up recruiting a similar number of seedlings. Acorns emerged seedlings 3.4 times farther in the crop failure year than in the crop success year. Cattle grazing was the main constraint on seed dispersal distance, reducing it by 51% during the extreme crop failure year, while having no noticeable effect during the successful crop year. Our study provides empirical evidence that cattle grazing modulates how an extreme crop failure year can surprisingly be an opportunity for trees remaining fecund to have seedlings established farther apart than in a crop success year. If we are to better manage and preserve the high conservation and socio-economic value of Mediterranean cork oak woodlands in the face of climate change, we must prioritize fecund trees and carefully manage seed dispersal factors such as cattle grazing, particularly during years of crop failure.

ecology↗

bioRxiv2021

Carnivores cross irrigation canals more often through overpasses than through culverts

As rainfall becomes scarcer or more erratic, we rely more on irrigation systems for water provision. Impacts of irrigation canals such as the barrier effect on wildlife movements are poorly documented. Although canal culverts and overpasses can be used by wildlife, little is known about their crossing patterns to guide barrier effect mitigation efforts. Over 7 years, we recorded medium-sized carnivore crossings by video-surveillance through 30 culverts and 28 overpasses in a large irrigation project in south-central Portugal. We examined the influence of the structures features and landscape context on the likelihood of canal crossing. Culvert crossings were positively influenced by the proportion of nearby montado, a high nature value farming system. Overpass crossings were more likely in areas away from paved roads and with more nearby wetlands. Overpasses increased the crossing rates by about 11 % relative to culverts and both were crossed more often in landscapes with evenly distributed land uses. In the project area, 20% of the montado has recently transitioned to irrigated agriculture, and wetlands have increased by 43%. It is therefore plausible that the increase in the crossing rate of overpasses relative to culverts will be accentuated. Our study produced the first evidence of a contrast in crossing rates among irrigation canal crossing structures. We have shown that the landscape can be a driver of animal crossings but irrigation projects can in turn be transformative of the landscape. Broadly, the fact that the deployment of irrigation canals may favor some land uses over others creates a conundrum that needs careful consideration when planning barrier effect mitigation interventions.

ecology↗

bioRxiv2020

Heavily burned wood from wildfires is less likely to provide substrate for stream biota

O_LIIncreasingly severe forest fires are recruiting more heavily burned wood into streams. Wood affects every ecological and physical process in streams differently throughout seasons. However, little is known about the seasonality of wood functions in fire-prone biomes and how it combines with wood burning level to guide future postfire restoration efforts. C_LIO_LIThrough an extensive three-year seasonal tracking of stream wood following forest fires in central Portugal, we examined for the first time the influence of burning level, season, and a large suite of driving factors on the likelihood of each of four functions with primary ecological consequences -- retention of organic matter, serving as substrate for aquatic biota, being key pieces forming wood jams, and deflecting flow including pool habitat formation. C_LIO_LIOur results strongly support that one of the main ecological functions of wood in rivers, i.e. to provide substrate for biological organisms -- namely for vegetation, periphyton, biofilms, and ovipositions -- can be negatively affected in heavily burned wood. C_LIO_LIExcept for jam formation, the probability of each stream wood function changed markedly with season and the probability of non-function was nearly twice as high in the Euro-Mediterranean dry as in the wet season. C_LIO_LIMore anchored and decayed wood increased the probability of all functions, whereas the effect of submergence depended on the function. Challenging the "size paradigm" assuming larger-sized pieces to provide more function, our data suggest the effect of size to be function-specific. C_LIO_LISynthesis and applications. We show how postfire restoration success can be maximized by selecting the most appropriate wood, taking advantage of attribute-function relationships and choosing the right timing for operations. We urge managers to refrain from removing wood or to selectively remove the most heavily carbonized only, allowing the persistence of great potential to provide substrate for stream biota. The non-attraction of heavily burned wood as substrate can be compensated for by other wood with attributes enhancing this function, such as wood deeper within the bankfull area, and with large diameters. These results help to inform successful management, as is increasingly asked from restoration ecology. C_LI

ecology↗

bioRxiv2019

Carnivore endozoochory of a dry fruited tree can benefit quarry passive restoration

As more work assert passive restoration as a complementary approach to technical reclamation, it is imperative to know its drivers. Although the consequences of endozoochory are crucial to predict passive restoration success, few experimental studies assess the use of heavily disturbed sites by seed dispersers such as carnivores and how the seeds they bring in emerge and survive. Using an indoor sowing experiment conducted in situ, we examined for the first time how carnivore endozoochorous seeds collected in a quarry potentially influence its passive restoration, through effects on plant emergence and survival. Also, we tested whether sowing date and water soaking, relevant factors when sowings are to be carried out, would affect seedling emergence and survival rates when compared with the effect of endozoochory. Most interesting in our analysis were the results for Carob tree (Ceratonia siliqua), a dry-fruited species being used in an ongoing action of artificial revegetation of this quarry located within a natural park in Portugal. Irrespective of the carnivore species, endozoochorous carob seeds collected in the quarry performed similarly to untreated seeds regarding emergence rates. Endozoochorous carob seedlings showed greater mortality rates but the net result for the plant can still be the colonization of recently vacant habitats by a large proportion of viable seeds. The later carob seeds were sown, the faster seedlings emerged, including endozoochorous seedlings. As expected, water soaking implied faster emergences. Broadly, plantings, sowings with previous soaking, and carnivore-mediated seed dispersal of this dry-fruited tree can jointly enhance quarry restoration. Implications for practiceO_LIRestorers can undertake pilot sowing experiments similar to ours prior to large scale revegetation campaigns to identify which species can benefit the most from endozoochory. C_LIO_LICarnivores in the surroundings of a quarry contribute a large proportion of viable seeds, likely assisting quarry passive restoration. C_LIO_LICarnivores ingesting carob seeds later in the fruiting season may assist quarry passive revegetation more readily as seeds ingested around that time emerge earlier. C_LIO_LIImmersion in tap water seems to be a simple, inexpensive, and a highly efficient method to break physical dormancy when carob seed sowings are to be carried out in degraded sites. C_LI

ecology↗

bioRxiv2018

Unravelling associations between tree seedling performance, herbivory, competition, and facilitation in high nature value farmlands

Herbivory, plant facilitation, and competition have complex impacts on tree regeneration which are seldom investigated together. Grazing exclosure experiments have allowed to quantify the effects of large herbivores on tree regeneration dynamics but have often ignored the effect of herbivorous insects. We experimentally tested how folivory (percentage of leaf damaged by insects), and microenvironment (tree-canopy cover and herbs) jointly alter performance (growth and survival) of seedlings of two dominant Mediterranean oak-species within ungulate exclosures. An agroforestry system dominated by cork oak (Quercus suber) and holm oak (Q. rotundifolia) was assessed in south-east Portugal. We aimed also to determine whether the two oak-species differ in the interdependences between folivory, microenvironment, covaring factors, and seedling performance. Unexpectedly, under the low-moderate insect defoliation occurred in our 3-year field study, growth and survival of cork and holm oak-seedlings were positively associated with herbivory damage. Herb removal increased oak folivory by 1.4 times. Herb removal was also positively associated with growth, directly and indirectly through its negative effect on oak folivory. Tree-canopy favored insect folivory upon cork oak seedlings directly and upon holm oak indirectly via decreasing light availability. Folivory was threefold greater upon cork than upon holm oak-seedlings. Our study shows that tree-canopy, herbs, and covarying factors can affect cork and holm oak-seedling performances through complex pathways, which markedly differ for the two species. The combined effect of insect herbivory and positive and negative plant-plant interactions need to be integrated into future tree regeneration efforts toward tackling the regeneration crisis of oak agroforestry systems of the Mediterranean.

ecology↗