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
6 results
Search Results
Now showing 1 - 6 of 6
Item Data on samara morphology and wind dispersal in the invasive tree Ailanthus altissima(2019) Planchuelo, Greg; Catalán, Pablo; Delgado Sáez, Juan Antonio; Murciano Cespedosa, AntonioThe data presented in this paper is supporting the research article “Estimating wind dispersal potential in Ailanthus altissima: The need to consider the three-dimensional structure of samaras” [1]. We analyzed the estimation of samara's wind dispersal potential through a group of morphological variables that succeed in describing the three-dimensional nature of samaras. We present here a dataset containing 8 morphological variables of 200 samaras belonging to 5 different individuals of the invasive tree Ailanthus altissima (Mill.) Swingle. Additionally, we present the average descent velocity of each of the samaras, which was recorded by releasing 5 times each samara under controlled and reproducible conditions. The data set is structured in a single spreadsheet where we also included the samara and the individual identity code of the tree.Item How deep must we dig? Sampling depth effects on root biomass assessment in mediterranean riparian buffers(Plant Biosystems, 2012) Delgado Sáez, Juan Antonio; González-Garrido, Laura; Martínez Martínez, TeodoraRoot turnover is a relevant process controlling carbon and nutrient cycles. Furthermore, root biomass could influence the effectiveness of riparian buffer systems with regard to immobilizing and processing soil water pollutants and improving soil quality. However, sampling root biomass presents many technical problems, because there is as yet no well-established method for assessment thereof. In the present study, we evaluated the effects of limited sampling depth on biomass assessment in four riparian buffers and on two different dates (January and June): a poplar forest, two mixed deciduous afforestations of different ages, and a grassy area. Although, for all systems, most root biomass was limited to the first 30 cm, detection of differences in root biomass among vegetation types depended strongly on sampling depth for both sampling dates. Furthermore, although the poplar forest presented one of the most stable root systems in terms of total biomass between the sampling dates, it was one of the most seasonally dynamic in terms of the amount and distribution with depth of root biomass. The results of this study suggest that a minimum sampling depth should be established for each study according to seasonal variation in vertical distribution of root biomass.Item 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 Effects of fertilization and neighbour removal on biomass allocation and fruit production in Cistus ladanifer(Plant Biosystems, 2011) Delgado Sáez, Juan Antonio; Serrano Talavera, José Manuel; López, F.; Acosta, F. J.The aim of this article was to assess short-term (11 months) changes in vegetative biomass allocation and in reproductive output in response to increased nutrient availability and to different intra-specific competition scenarios in adult C. ladanifer plants. We performed a factorial field experiment with four treatments: (1) no fertilization and no neighbour removal, (2) fertilization (400 kg ha71 of controlled release NPK fertilizer) and no neighbour removal, (3) no fertilization and neighbour removal (all vegetation growing within a 2 m radius around the target plant were cut) and (4) fertilization and neighbour removal. We found a significant interaction between fertilization and neighbour removal affecting patterns of biomass allocation; plants without neighbours allocated relatively more biomass to leaves and less to branches only in the nonfertilized group, with no evident effect on the fertilized one. Furthermore, the positive effects of neighbour removal on number and biomass of fruits were appreciable regardless of nutrient conditions, which suggest that competition intensity was independent from soil fertility.Item Reducing visitors’ group size increases the number of birds during educational activities: Implications for management of nature-based recreation(Journal of Environmental Management, 2011) Remacha Sebastián, Carolina; Pérez Tris, Javier; Delgado Sáez, Juan AntonioOrganized tours to watch wildlife are popular recreational and educational activities, in which the visitor expectative (to observe as many and as diverse animals as possible) runs parallel to conservation purposes. However, the presence of visitors may cause negative impacts on wildlife, which makes recreation difficult to manage. Thus, restricting visitor’s load to minimize impacts on fauna may be advisable, but too much restriction may end up disappointing the public. We analysed how visitors’ group size influences the number and variety of birds observed during an educational activity directed to scholars, in a forested area where public access is otherwise restricted.We observed fewer birds, but not fewer species, as the size of scholars’ groups increased. Such effect was apparently mediated by a few species demonstrating reduced tolerance to increased group size. Our results support the idea that reducing the size of visitors’ groups not only helps to minimize the negative impacts on wildlife derived from leisure activities, but also allows visitors to watch more wildlife. Therefore, organizing visitors in small numbers is recommended in the design of activities directed to groups of people visiting natural areas.Item Evaluating the Role of Introductory Lessons in Outdoor Environmental Activities(Journal of Environmental Protection and Ecology, 2012) Plaza, S.; Rabanal, J. M.; Delgado Sáez, Juan AntonioWe assessed the independent impacts both of an introductory in-class lesson and an outdoor lesson on test scores in a group of Spanish schoolchildren. Our main aim was to assess whether either type of lesson interacted or whether their effects were additive. We tested total of 139 grade 4 students (age 9–10) from 4 Spanish primary schools using a factorial design, taking into account school and student gender. The outdoor experience consisted of a talk on the main species of flora and fauna (birds and mammals) during a walk through the forest and also included a set of rules for good conduct. The introductory lessons at the schools consisted of a talk on the same topics with the aid of pictures. Following the lessons, selected students filled in a questionnaire which we used to evaluate increased knowledge. The results showed that outdoor activity, training lesson and school had a strong influence on total score. However, we have not found a synergic effect between the training lesson and the outdoor activity. Thus, it was concluded that a previous in-class lesson increased students knowledge and, although it was not obligatory to obtain the benefits of the outdoor activity, it might be useful with regard to linking in-class and outdoor environments.