María Dolores Jiménez

Alert distance as an alternative measure of bird tolerance to human disturbance: implications for park design

Animal tolerance to human approaches may be used to establish buffers for wildlife that can minimize the probability that animals will be disturbed by human activity. Alert distance (the distance between an animal and an approaching human at which point the animal begins to exhibit alert behaviours to the human) has been proposed as an indicator of tolerance mainly for waterbirds; however, little is known about its utility for other bird species. The factors that influenced alert distances of four bird species to pedestrian approaches in five large wooded fragments in the city of Madrid (Spain) were analysed. Location of human activity affected only Passer domesticus alert distances, which increased in the proximity of pathways. Habitat structure modified alert distances of all the species ( Passer domesticus , Turdus merula , Columba palumbus , and Pica pica ), increasing bird tolerance with greater availability of escape cover (shrub and coniferous cover, and shrub height). Alert distances varied among species, with large species being less tolerant of human disturbance than small ones. Alert distance appears to be a more conservative indicator of tolerance than flight distances, because it includes a buffer zone (the difference between alert and flight distance) in which birds may adapt their reaction to the behaviour of visitors. Alert distance may be used in the determination of minimum approaching areas, allowing people to enjoy their visit to parks, and birds to use patches for foraging and breeding without being displaced.

Bird tolerance to human disturbance in urban parks of Madrid (Spain): Management implications

The effects of human disturbance in urban parks of Madrid (Spain) on bird tolerance were studied to derive recommendations for urban park planning. We intended to determine (1) how habitat structure influenced flush distances, (2) whether flush distance increased with body-size, and (3) whether flush distances varied with the amount of people visiting the park. In four city parks in Madrid with different levels of human visitation and habitat structure, we recorded flush distances of four bird species of different sizes (overall body length: Passer domesticus, 15 cm; Turdus merula, 24–25 cm; Columba palumbus, 40–42 cm; Pica pica, 44–48 cm). Humans approached individual birds when they were foraging on the ground. Habitat structure (shrub cover, shrub and tree height) influenced flush distances of the four species. After controlling for the effects of different microhabitat use, averaged flush distances varied significantly among species; large species were less tolerant of human disturbance than small ones. Birds were more tolerant of our intrusions in parks with more human visitors. To enhance the suitability of urban parks for bird species, the following recommendations may be considered: (a) flush distances could be a first indicator of appropriate set-back distances (minimal distance that a pedestrian may approach a bird) for pathways, (b) flush distances of large bird species could be used to determine minimum area requirements of resource patches separated by pathways, (c) habitat complexity could increase the availability of escape cover for native bird species, and (d) highly variable visitation rates may be less harmful in popular parks, because bird tolerance to human disturbance appears to increase with the overall amount of visitors per park.

Interactive responses of Quercus suber L. seedlings to light and mild water stress: effects on morphology and gas exchange traits

Abstract• The combined effect of water stress and light on seedlings of forest species is a key factor to determine the best silvicultural and afforestation practices in the Mediterranean area.• The aims of this work was (1) to determine the optimal light level for the early development of cork oak seedlings under mild water stress and (2) to test if the combined effect of water stress and light followed the trade-off, the facilitation or the orthogonal hypothesis.• Shade reduced instantaneous photosynthetic rates and water use efficiency in cork oak. However, seedlings grown under moderate shade (15% of full sunlight) were capable to accumulate similar amount of biomass than those grown under more illuminated environments by increasing their specific leaf area. Absolute differences in net photosynthesis between light treatments were higher in well watered than in water stressed seedlings. However, the impact of both factors on overall growth was orthogonal.• We concluded that cork oak development is impaired under deep shade (5% of full sunlight) but it can be optimal under moderate shade (15% of full sunlight) even under moderate water stress. Implications of these patterns on regeneration, cultivation and afforestation of cork oak are discussed.Résumé• L’effet combiné du stress hydrique et de la lumière sur les semis est un facteur clé pour déterminer les meilleures pratiques pour la sylviculture et le reboisement dans la région méditerranéenne.• Le but de ce travail a été (1) de déterminer le niveau optimal de lumière pour le développement précoce des semis de chêne liège soumis à un stress hydrique modéré et (2) de tester si l’effet combiné du stress hydrique et de la lumière suit l’hypothèse de compensation, de facilitation ou d’orthogonalité.• L’ombre réduit le taux instantané de photosynthèse et l’efficience d’utilisation de l’eau chez le chêne liège. Cependant, les semis qui ont poussé sous une ombre modérée (15 % de la pleine lumière) ont été capables d’accumuler une biomasse totale similaire à celle des semis qui ont poussé sous de meilleures conditions d’éclairement en accroissant leur surface foliaire spécifique. Les différences absolues pour la photosynthèse nette, entre les traitements lumineux, ont été plus importantes pour les traitements bien alimentés en eau que pour les semis soumis à un stress hydrique. Cependant, l’impact des deux facteurs sur l’ensemble de la croissance a été orthogonal.• Nous en avons déduit que le développement du chêne liège est diminué sous une ombre profonde (5 % du plein éclairement) mais il peut être optimal sous une ombre modérée (15 % du plein éclairement) même en conditions de stress hydrique modéré. Les implications de ces modèles pour le chêne liège ont été discutées pour ce qui concerne la régénération, la culture et le reboisement.

Forest Restoration in a Fog Oasis: Evidence Indicates Need for Cultural Awareness in Constructing the Reference

Background In the Peruvian Coastal Desert, an archipelago of fog oases, locally called lomas, are centers of biodiversity and of past human activity. Fog interception by a tree canopy, dominated by the legume tree tara (Caesalpinia spinosa), enables the occurrence in the Atiquipa lomas (southern Peru) of an environmental island with a diverse flora and high productivity. Although this forest provides essential services to the local population, it has suffered 90% anthropogenic reduction in area. Restoration efforts are now getting under way, including discussion as to the most appropriate reference ecosystem to use. Methodology/Principal Findings Genetic diversity of tara was studied in the Atiquipa population and over a wide geographical and ecological range. Neither exclusive plastid haplotypes to loma formations nor clear geographical structuring of the genetic diversity was found. Photosynthetic performance and growth of seedlings naturally recruited in remnant patches of loma forest were compared with those of seedlings recruited or planted in the adjacent deforested area. Despite the greater water and nitrogen availability under tree canopy, growth of forest seedlings did not differ from that of those recruited into the deforested area, and was lower than that of planted seedlings. Tara seedlings exhibited tight stomatal control of photosynthesis, and a structural photoprotection by leaflet closure. These drought-avoiding mechanisms did not optimize seedling performance under the conditions produced by forest interception of fog moisture. Conclusions/Significance Both weak geographic partitioning of genetic variation and lack of physiological specialization of seedlings to the forest water regime strongly suggest that tara was introduced to lomas by humans. Therefore, the most diverse fragment of lomas is the result of landscape management and resource use by pre-Columbian cultures. We argue that an appropriate reference ecosystem for ecological restoration of lomas should include sustainable agroforestry practices that emulate the outcomes of ancient uses.

Can a solitary avian species use collective detection? An assay in semi-natural conditions

Collective detection (e.g., enhanced predator detection through the vigilance of conspecifics) is expected to have evolved particularly in social species. However, we assessed the degree to which an avian territorial species (California towhee Pipilo crissalis) would use social cues about predation in a semi-natural assay. We also exposed a social species (house finch Carpodacus mexicanus) to similar conditions. California towhees increased scanning rates when foraging with conspecifics, whereas house finches increased scanning rates when foraging solitarily, suggesting that vigilance in these species is regulated mostly through interference competition and through predation risk, respectively. California towhees did not show early detection, and actually the last detector in the group delayed detection in relation to solitary individuals. House finches benefited from early detection, but the second and last detectors maintained detection at the level of solitary individuals. California towhees increased the chances of fleeing when in groups in relation to solitary conditions, but this effect was less pronounced in the last detector. House finches always fled across conditions. Overall, an asocial avian species may use collective detection, but limited to certain types of cues: responses were more pronounced to overt (conspecifics walking or fleeing) rather than subtle (conspecifics becoming alert or crouching) social cues.

Field patterns of temporal variations in the light environment within the crowns of a Mediterranean evergreen tree (Olea europaea)

Key messageThere are specific diurnal light variation patterns and negligible seasonal variation within tree crowns. Crown-mediated regulation of temporal light regimes can be important for whole plant function in Mediterranean evergreens.AbstractThe light environment within a tree crown can be characterized by specific variation patterns arising from the structural features of the crown. Within-crown light variation patterns can be important for plant productivity, but this has yet to be assessed in natural settings. The spatio-temporal variations of direct and diffuse photosynthetic photon flux density (PPFD), their proportions and sunfleck frequency within the crowns of isolated adult wild olive trees (Olea europaea L.) were investigated. Trees growing in contrasting Mediterranean conditions (continental vs. coastal) at the same latitude were compared. Instantaneous diffuse and total PPFD were measured with sunshine sensors in three crown layers (outer-, middle- and inner-crown) in the south-facing part of the crown, at two points of the diurnal (mid-morning and midday) and seasonal (summer and winter) cycles. Direct PPFD and the proportion of direct to total PPFD vary diurnally within the crown as a result of an increase in sunfleck frequency during midday and in self-shading during mid-morning, in both summer and winter conditions. Conversely, the lack of seasonal variation in the three light attributes is better explained by a greater average crown transmittance in winter conditions. The interplay between crown architecture heterogeneity and varying solar position renders identifiable patterns of temporal variations in the light environment within tree crowns. These patterns suggest that trees can benefit from the light heterogeneity typical of Mediterranean environments by developing conservative architectural layouts.

Use of restoration plantings to enchance bird seed dispersal at the roadside: failures and prospects

AbstractPlantings are commonly used in roadside reclamation for ornamental purposes and for increasing slope stability and road safety. However, the role of these plantings in restoring ecological processes, such as seed dispersal, has received little attention. We carried out a study to assess the potential role of plantings on roadside embankments to attract frugivorous birds and to enhance seed dispersal mediated by birds from the surrounding landscape. We examined: (1) bird species richness and abundance; (2) patterns of avian spatial distribution within embankments and (3) seed dispersal mediated by birds. Bird richness and abundance did not differ between embankments with and without plantings. However, birds were not distributed randomly within embankments, with levels of species richness and abundance for facultative frugivorous between 4.8–8 times higher in areas closer to plantings. An analysis of bird droppings showed that birds only dispersed seeds of the planted species since no seeds of wood...

Local plant responses to global problems: Dactylis glomerata responses to different traffic pollutants on roadsides

The growing number of road vehicles is a major source of regional and global atmospheric pollution increasing concentrations of CO2 in the air, and levels of metals in air and soil. Nevertheless, the effects of these pollutants on plants growing at roadsides are poorly documented. We carried out an observational study of unmanipulated plants growing by the road, to identify the morpho-physiological responses in a perennial grass Dactylis glomerata. Firstly, we wanted to know the general effect of traffic intensity and ambient CO2 and its interactions on different plant traits. Accordingly, we analyzed the photosynthetic response by field A/Ci Response Curves, SLA, pigment pools, foliar nitrogen, carbohydrates and morphological traits in plants at three distances to the road. Secondly, we wanted to know if Dactylis glomerata plants can accumulate metals present on the roadside (Pb, Zn, Cu, and Sr) in their tissues and rhizosphere, and the effect of these metals on morphological traits. The MANCOVA whole model results shown: 1) a significant effect of road ambient CO2 concentration on morphological traits (not affected by traffic intensity, P interaction CO2 x traffic intensity>0.05), that was mainly driven by a significant negative relationship between the inflorescence number and ambient CO2; 2) a positive and significant relationship between ambient CO2 and the starch content in leaves (unaffected by traffic intensity); 3) a reduction in Jmax (electron transport rate) at high traffic intensity. These lines of evidences suggest a decreased photosynthetic capacity due to high traffic intensity and high levels of ambient CO2. In addition, Pb, Cu, Zn and Sr were detected in Dactylis glomerata tissues, and Cu accumulated in roots. Finally, we observed that Dactylis glomerata individuals growing at the roadside under high levels of CO2 and in the presence of metal pollutants, reduced their production of inflorescences.