Person: Delgado Sáez, Juan Antonio
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First Name
Juan Antonio
Last Name
Delgado Sáez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Biológicas
Department
Biodiversidad, Ecología y Evolución
Area
Ecología
Identifiers
5 results
Search Results
Now showing 1 - 5 of 5
Item Erratum to: Field patterns of temporal variations in the light environment within the crowns of a Mediterranean evergreen tree (Olea europaea)(Trees, 2016) Ventre-Lespiaucq, Agustina B.; Escribano Rocafort, Adrián Gaspar; Delgado Sáez, Juan Antonio; Jiménez Escobar, María Dolores; Rubio de Casas, Rafael; Granado Yela, Carlos; Balaguer Núñez, LuisItem Spatial and demographic structure of tara stands (Caesalpinia spinosa) in Peru: Influence of present and past forest management(Forest Ecology and Management, 2016) Cordero, I.; Jiménez Escobar, María Dolores; Delgado Sáez, Juan Antonio; Villegas, L.; Balaguer Núñez, LuisTropical dry forests are highly endangered ecosystems that have been scarcely studied. Many species within these forests suffer regeneration problems due to unsustainable management regimes. In particular, a regeneration problem has been detected in a forest of tara (Caesalpinia spinosa), a neotropical tree of high ecological and economic value, in Atiquipa (Peru). The study of the spatial patterns and population structure of forests can help us understand their dynamics and evaluate the effects of management. In this article, we analyse the stand demographic structure, spatial distribution and patterns of plant interactions in tara forests. We evaluate whether the regeneration problem in Atiquipa is strictly local or a problem of general concern and investigate the most probable causes. Four tara stands were selected at different localities in Peru. Two stands (Andurco and Polán) had a reverse J-shaped diametric structure, typical of stable self-replacing forests, although Polán had a low number of young trees, indicating an incipient regeneration problem. The Lloque histogram was skewed (with a maximum in seedlings 61 cm), indicating over-exploitation in the past and present forest regeneration. Maguey had a low number of regenerates, with peaks in some intermediate diametric classes, which may indicate natural regeneration problems or some past management. Spatial distribution of tara trees did not depart from the null model (�random distribution), typical of trees dispersed by zoochory. Maguey was an exception, showing a regular pattern at short distances, possibly associated with past management (like selective cuttings and/or plantations). These results suggest that in most of the analysed stands the current forest management (i.e. excessive seed collection or grazing) limits tara forest regeneration. However, the only stand with a protected status presented a clear tendency toward population increase. Bivariate analyses revealed an aggregated pattern between seedlings and adult trees. Moreover, the plant-plant interaction study showed that seedlings were associated with woody vegetation. These positive associations highlight a facilitative effect that ameliorates stressful microclimatic characteristics and/or protects tara seedlings from herbivory. The results of this study support some recommendations for sustainable management, such as controlled stocking rate, limited seed collection and promotion of bush cover.Item Simplifying data acquisition in plant canopies- Measurements of leaf angles with a cell phone(Methods in Ecology and Evolution, 2014) Escribano-Rocafort, Adrián G.; Ventre-Lespiaucq, Agustina B.; Granado Yela, Carlos; López-Pintor Alcón, Antonio; Delgado Sáez, Juan Antonio; Muñoz, Vicente; Dorado, Gabriel A.; Balaguer Núñez, Luis1.Canopies are complex multilayered structures comprising individual plant crowns exposing a multifaceted surface area to sunlight. Foliage arrangement and properties are the main mediators of canopy functions. Theleaves act as light traps whose exposure to sunlight varies with time of the day, date and latitude in a trade-off between photosynthetic light harvesting and excessive or photoinhibitory light avoidance. To date, ecological research based upon leaf sampling has been limited by the available technology, with which data acquisition becomes labour intensive and time-consuming, given the overwhelming number of leaves involved. 2. In the present study, our goal involved developing a tool capable of measuring a sufficient number of leaves to enable analysis of leaf populations, tree crowns and canopies. We specifically tested whether a cell phone working as a 3D pointer could yield reliable, repeatable and valid leaf angle measurements with a simple gesture. We eval-uated the accuracy of this method under controlled conditions, using a 3D digitizer, and we compared perfor-mance in the field with the methods commonly used. We presented an equation to estimate the potential proportion of the leaf exposed to direct sunlight (SAL) at any given time and compared the results with those obtained by means of a graphical method. 3.We found a strong and highly significant correlation between the graphical methods and the equation presented. The calibration process showed a strong correlation between the results derived from the two methods with a mean relative difference below 10%. The mean relative difference in calculation of instantaneous exposure was below 5%. Our device performed equally well in diverse locations, in which we characterized over 700 leaves in a single day. 4.The new method, involving the use of a cell phone, is much more effective than the traditional methods or digitizers when the goal is to scale up from leaf position to performance of leaf populations, tree crowns or canopies. Our methodology constitutes an affordable and valuable tool within which to frame a wide range of ecological hypotheses and to support canopy modelling approaches.Item Sink strength manipulation in branches of a Mediterranean woody plant suggests sink-driven allocation of biomass in fruits but not of nutrients in seeds(Acta Physiologiae Plantarum, 2016) Catalán, Pablo; Delgado Sáez, Juan Antonio; Jiménez Escobar, María Dolores; Balaguer Núñez, LuisThe relative autonomy of branches within an individual plant may favor different resource allocation responses after reproductive losses. The assessment of these reproductive strategies at the branch level before their integration at the plant level would provide more insight into how plants deal with reproductive losses. Here, we present a field experiment to assess changes in the allocation strategies at the branch level after sink strength manipulation in a Mediterranean woody plant (Cistus ladanifer). We applied three levels of removal of developing fruits (75, 25 and 0 %) on branches of the same plants, and measured their effects on resource allocation (biomass, nitrogen and phosphorus) and seed production after controlling for the effects of branch diameter and leaf weight per branch. Our results suggest that after experimental fruit thinning, C. ladanifer branches presented a sink-driven allocation of biomass to fruits but this was not the case for the allocation of nutrients to seeds, which could be driven by competition with leaf biomass. Reductions in biomass per fruit resulted in a reduction in seed output since the average weight per seed remained constant. From these results, it could be suggested that an heterogeneous distribution of fruit losses among the branches within a crown would produce a higher impact on reproductive output than a more equitable distribution.Item Field patterns of temporal variations in the light environment within the crowns of a Mediterranean evergreen tree (Olea europaea)(Trees, 2016) Ventre-Lespiaucq, Agustina B.; Escribano Rocafort, Adrián Gaspar; Delgado Sáez, Juan Antonio; Jiménez Escobar, María Dolores; Rubio de Casas, Rafael; Granado Yela, Carlos; Balaguer Núñez, LuisThe 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 requency 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.