Open Access
Environment and density-dependency explain the fine-scale aggregation of tree recruits before and after thinning in a mixed forest of Southern Europe
(PeerJ, 2022) Rodríguez Pérez, Javier; Peralta de Andrés, Francisco Javier; Imbert Rodríguez, Bosco; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias
Thinning in forest management primarily reduces the density of trees and alters the patchiness and spatial complexity of environmental factors and individual interactions between plant recruits. At fine spatial scales, little is known about the relative weight of ecological processes affecting tree regeneration before and after thinning events. Here we studied the density and aggregation of tree recruits in fully-mapped plots located in mixed forests in Northern Iberian Peninsula (Southern Europe) for over four years, which comprises one year before and three years after a thinning event. We applied spatial point-pattern analyses to examine (a) the aggregation of recruits, and their association with trees and (b) the relative effect of both environmental (i.e., the patchiness of the local environment) and density-dependent factors (i.e., the aggregation of trees and/or recruits) to predict the density, aggregation, and survival of recruits. We found, in thinning plots, that recruits were less dense, their aggregation pattern was more heterogeneous, were distributed randomly in respect of trees and their survival was almost unaffected by the tree proximity. By contrast, recruits in control plots were denser, were only aggregated at distances lower than 1.0 m, were closer to trees, and such closer distance to trees affected negatively in their survival. Independently of the treatment, the aggregation of recruits was chiefly determined by the density-dependent factors at less than 1.0 m and environmental factors at distances beyond that proximity. Overall, our results suggest that thinning affected the aggregation of recruits at two spatial scales: (a) by favoring the tree-recruit and recruit-recruit facilitation at less than 1.0 m and (b) by modifying spatial heterogeneity of the environment at distances beyond that proximity.
Open Access
Abundance and trait-matching both shape interaction frequencies between plants and birds in seed-dispersal networks
(Elsevier, 2023) Peña, Rocío; Schleuning, Matthias; Dalerum, Fredrik; Donoso, Isabel; Rodríguez Pérez, Javier; García, Daniel; Institute for Multidisciplinary Research in Applied Biology - IMAB
Abundance and trait-driven processes have both been identified as potential mechanisms in determining the occurrence of species interactions. However, little is known about how these two mechanisms interact to determine the relative frequencies of interactions between species, and thereby species-specific contributions to ecological functions. Here, we evaluate the effect of both species¿ abundance and trait-matching on the occurrence of plant-bird seed dispersal interactions in the Cantabrian Range (northern Spain). For two years at fourteen plots, we independently sampled the abundance and diversity of fleshy-fruited plants and frugivores, as well as the consumption of fruits by birds. We quantified trait-matching by applying a food-web approach based on the log-ratios of species traits relevant to seed dispersal and traits related to fruit-handling and foraging-stratum. We fitted multi-level models incorporating phylogenetic relatedness to identify phylogenetically independent effects of species abundance and trait-matching on interaction frequencies. Fitted models showed that species abundances of both plants and birds always had strong positive effects on interaction frequencies. Trait-matching effects associated with fruit-handling were weak, but consistent across years, whereas those derived from foraging stratum varied across years, according to strong interannual changes in species abundance. Our findings reveal that both species abundance and functional traits are required for a mechanistic understanding of species interactions, as well as for predicting species roles in ecosystems under global change.
Open Access
Disentangling the seasonal effects of agricultural intensification on birds and bats in Mediterranean olive groves
(Elsevier, 2023) Jiménez Navarro, Gerardo; Rodríguez Pérez, Javier; Melguizo Ruiz, Nereida; Silva, Bruno; Vasconcelos, Sasha; Beja, Pedro; Moreira, Francisco; Morgado, Rui; Barreiro, Silvia; Herrera, José M.; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB
Assessing the spatio-temporal impact of agricultural intensification on species and communities is key for biodiversity conservation. Here, we investigated the seasonal effects of olive grove intensification at both local (farming practices and grove structural complexity) and landscape scale (land-cover diversity) on birds and bats, at species and community-level. Both groups were surveyed during spring, summer, and autumn in 60 sites representing varying levels of olive grove intensification throughout the Alentejo region (southern Portugal). At the local scale, the number of chemical applications was used as a proxy for the intensification of farming practices and a Structural Index, which accounted for within-grove variability in tree density and features, was used as a measure of grove structural complexity. At landscape scale, we quantified the proportion of the major land-cover types potentially affecting birds and bats. We found that the abundance of ca. 77% of the species analyzed (ca. 84% and 55% of birds and bats respectively) was negatively related to olive grove intensification in at least one season. The Structural Index was the most influential factor at both species and community-levels, especially for birds, with a consistent and strong effect across seasons. Chemical applications had a stronger negative effect on birds, whereas the amount of olive grove cover had a stronger detrimental effect on bats. Birds and bats showed a variable response to predictor variables depending on the season, particularly for the bat community. Our study shows differences in bird and bat responses associated with the spatio-temporal variability of the agricultural intensification components. On the one hand, birds and bats showed a seasonal pattern of association with the different components of olive grove intensification, probably due to their ecological and biological requirements. On the other hand, the responses of both groups also appear to be scale-dependent: while birds seem to respond to in-farm or local intensification more strongly, bats seem to be more influenced by landscape-scale simplification. Overall, we highlight the importance of the structural complexity of olive groves for birds and bats, an aspect that should be considered in the design of agricultural policies aiming to promote biodiversity conservation.
Open Access
Changes in long-term light properties of a mixed conifer–broadleaf forest in Southwestern Europe
(MDPI, 2021) Ruiz de la Cuesta Vela, Ignacio; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Peralta de Andrés, Francisco Javier; Rodríguez Pérez, Javier; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Natural and anthropogenic factors affect forest structure worldwide, primarily affecting forest canopy and its light properties. However, not only stand-replacing events modify canopy structure, but disturbances of lower intensity can also have important ecological implications. To study such effects, we analyzed long-term changes in light properties of a conifer–broadleaf mixed forest in the Southwestern Pyrenees, placed in the fringe between the Mediterranean and Eurosi- berian biogeographical regions. At this site, a thinning trial with different intensities (0%, 20%, and 30–40% basal area removed) took place in 1999 and 2009, windstorms affected some plots in 2009 and droughts were recurrent during the sampling period (2003, 2005, 2011). We monitored light properties during 14 years (2005–2019) with hemispherical photographs. We applied partial autocorrelation functions to determine if changes between years could be attributed to internal canopy changes or to external disturbances. In addition, we mapped the broadleaf canopy in 2003, 2008, and 2016 to calculate broadleaf canopy cover and richness at the sampling points with different buffer areas of in- creasing surface. We applied generalized linear mixed models to evaluate the effects of light variables on canopy richness and cover. We found that light variables had the most important changes during the period 2008 to 2010, reacting to the changes caused that year by the combined effects of wind and forest management. In addition, we found that an area of 4.0 m radius around the sampling points was the best to explain the relationship between light properties and species richness, whereas a radius of 1.0 m was enough to estimate the relationship between light and canopy cover. In addition, light-related variables such as diffuse light and leaf area index were related to species richness, whereas structural variables such as canopy openness were related to canopy cover. In summary, our study demonstrates that non stand-replacing disturbances such as windstorms, thinning, or droughts can have an important role in modifying structural and light-related canopy properties, which in turn may inﬂuence natural processes of stand development and ecological succession.
Open Access
Forest recovery through applied nucleation: effects of tree islet size and disperser mobility on tree recruitment in a temperate landscape
(Elsevier, 2023) Morán-López, Teresa; Rodríguez Pérez, Javier; Donoso, Isabel; Martínez, Daniel; Morales, Juan Manuel; García, Daniel; Ciencias; Zientziak
The plantation of tree islets within deforested areas (applied nucleation) has been proposed as a restoration strategy able to catalyze tree colonization in the matrix with reasonable costs and labor compared to traditional restoration methods such as extensive plantations. However, recent work has questioned its effectiveness in comparison to natural forest regeneration, and observational studies have eventually reported a limited expansion of tree islets after years of planting. To infer the processes affecting the effectiveness of applied nucleation, we used a stochastic model able to predict avian movement and fruit consumption, tree seed dispersal and seedling establishment in a fragmented temperate forest landscape of northern Spain. First, we simulated scenarios of natural regeneration and compared them to applied nucleation in terms of tree colonization in the remaining deforested matrix. Subsequently, in applied nucleation scenarios we assessed the effects of islet size and matrix area recovered on tree recruitment into the matrix. Also, we evaluated if such effects were mediated by the scale of movement of frugivores. Our results showed that applied nucleation triggers matrix colonization by trees at higher rates than natural regeneration because it avoids frugivore entrapment within forest edges. Also, that large tree islets can hamper matrix colonization despite being visited more frequently. If large tree islets offer abundant resources, animals do not need to leave their boundaries, concentrating seed deposition within islets. As expected, such effects depended on the scale of movement of frugivores. Our work highlights that in nucleated landscapes, islets harboring fruit-producing trees should attract animal dispersers, and also foster animal inter-islet movement. Both conditions should be met to ensure seed deposition and seedling establishment in the deforested matrix, promoting forest recovery independent of islet expansion through vegetative growth. To achieve these restoration goals, we propose establishing islets whose size and inter-islet distances matches the scale of movement of main seed dispersers present in the area.
Open Access
7ª Edición de la Escuela de verano de Ecología de Navarra: 'Biodiversidad, interacciones bióticas y funciones ecosistémicas'
(Asociación Española de Ecología Terrestre (AEET), 2021) Rodríguez Pérez, Javier; Blanco Vaca, Juan Antonio; Ciencias; Zientziak
Noticia de la celebración de la séptima edición de la Escuela de Verano de Ecología de Navarra, celebrada el 2 de septiembre de 2021, en la que se impartieron cuatro ponencias.
Open Access
A food web approach reveals the vulnerability of biocontrol services by birds and bats to landscape modification at regional scale
(Nature Research, 2021) Herrera, José M.; Silva, Bruno; Jiménez Navarro, Gerardo; Barreiro, Silvia; Melguizo Ruiz, Nereida; Moreira, Francisco; Vasconcelos, Sasha; Morgado, Rui; Rodríguez Pérez, Javier; Ciencias de la Salud; Osasun Zientziak
Pest control services provided by naturally occurring species (the so-called biocontrol services) are widely recognized to provide key incentives for biodiversity conservation. This is particularly relevant for vertebrate-mediated biocontrol services as many vertebrate species are of conservation concern, with most of their decline associated to landscape modification for agricultural purposes. Yet, we still lack rigorous approaches evaluating landscape-level correlates of biocontrol potential by vertebrates over broad spatial extents to better inform land-use and management decisions. We performed a spatially-explicit interaction-based assessment of potential biocontrol services in Portugal, using 1853 pairwise trophic interactions between 78 flying vertebrate species (birds and bats) and 53 insect pests associated to two widespread and economically valuable crops in the Euro-Mediterranean region, olive groves (Olea europaea subsp. europaea) and vineyards (Vitis vinifera subsp. vinifera). The study area was framed using 1004 square cells, each 10 × 10 km in size. Potential biocontrol services were determined at all those 10 × 10 km grid-cells in which each crop was present as the proportion of the realized out of all potential pairwise interactions between vertebrates and pests. Landscape correlates of biocontrol potential were also explored. Our work suggests that both birds and bats can effectively provide biocontrol services in olive groves and vineyards as they prey many insect pest species associated to both crops. Moreover, it demonstrates that these potential services are impacted by landscape-scale features and that this impact is consistent when evaluated over broad spatial extents. Thus, biocontrol potential by vertebrates significantly increases with increasing amount of natural area, while decreases with increasing area devoted to target crops, particularly olive groves. Overall, our study highlights the suitability of our interaction-based approach to perform spatially-explicit assessments of potential biocontrol services by vertebrates at local spatial scales and suggest its utility for integrating biodiversity and ecosystem services in conservation planning over broad spatial extents.