Browsing by Subject "Global change"

Now showing 1 - 4 of 4
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    Evaluating temporal turnover in avian species richness in a Mediterranean semiarid region: different responses to elevation and forest cover
    (2024) Jiménez Franco, María V.; Kéry, Mark; León Ortega, Mario; Martinez Rodenas, Jacinto; Robledano Aymerich, Francisco; Esteve Selma, Miguel A.; Calvo Sendin, José F.; Ecología e Hidrología
    Aim: When studying the effects of global change on biodiversity, it is far more common for the effects of climate change and land-use changes to be assessed separately rather than jointly. However, the effects of land-use changes in recent decades on species richness in areas affected by climate change have been less studied. We assess the temporal turnover in species richness of an avian community between a historical period and a modern one as a consequence of global change. Location: Semiarid Mediterranean ecosystem (southeastern Spain). Method: We fitted a hierarchical multispecies occupancy model for each period (1991–1992, and 2012–2017), obtaining avian species-specific estimates of occupancy probability in relation to environmental covariates (elevation and forest cover). We analyse the relationships between changes in the bird community and environmental variables, analysing the temporal turnover of the species richness and the richnessbased species-exchange ratio. Results: The estimated species richness accounting for detectability was higher than observed species richness, and decreased in the more recent period. Following our hypotheses, we observed a dual pattern of species richness increase associated with different elevations, showing different species turnover rates due to the joint effects of climate change and land-use change. There is a trend towards greater species richness with higher elevations that is associated with climate change, where the species turnover rate is low. Also, species richness increased towards lower elevations, but with a high turnover rate. The latter can be due to species expansions throughout new habitat configurations in bordering forest systems associated with anthropic land-use changes. Conclusions: Our study is of great interest to understand the temporal turnover of avian species richness associated with areas experiencing both climate and land-use change
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    Impacts of environmental filters on functional redundancy in riparian vegetation
    (Wiley / British Ecological Society, 2016-06) Bruno, Daniel; Gutiérrrez Cánovas, Cayetano; Sánchez Fernández, David; Velasco, Josefa; Nilsson, Christer; Ecología e Hidrología
    Understanding and predicting ecosystem responses to multiple environmental pressures is a long-standing interest in ecology and environmental management. However, few studies have examined how the functional features of freshwater biological communities vary along multiple gradients of environmental stress. Furthermore, modelling these functional features for a whole river network constitutes a strong potential basis to improve ecosystem management. We explored how functional redundancy of biological communities (FR, a functional feature related to the stability, resistance and resilience of ecosystems) responds to single and multiple environmental filters. We compared these responses with those of functional richness, evenness and divergence. We used riparian vegetation of a Mediterranean basin, and three of the main environmental filters affecting freshwater communities in such regions, that is drought, flow regulation and agricultural intensity, thus considering the potential effect of natural environmental variability. We also assessed the predictability of FR and estimated it for the entire river network. We found that all functional measures decreased with increasing environmental filter intensity. However, FR was more sensitive to single and multiple environmental filters compared to other functional measures. The best-fitting model explained 59% of the FR variability and included agriculture, drought and flow regulation and the pairwise interactions of agriculture with drought and flow regulation. The parameters of the FR models differed from null model expectations reflecting a non-random decline along stress gradients. Synthesis and applications. We found non-random detrimental effects along environmental filters' gradients for riparian functional redundancy (the most sensitive functional index), meaning that increased stress could jeopardize stability, resistance and resilience of these systems. In general, agriculture caused the greatest impact on functional redundancy and functional diversity measures, being the most important stressor for riparian functionality in the study area. Temporary streams flowing through an agricultural, regulated basin had reduced values of functional redundancy, whereas the free-flowing medium-sized, perennial water courses flowing through unaltered sub-basins displayed higher values of functional redundancy and potentially greater stability against human impacts. All these findings along with the predicted basin-wide variation of functional redundancy can assist environmental managers in improving monitoring and ecosystem management.
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    Open Access
    Long-term trends of local bird populations based on monitoring schemes: are they suitable for justifying management measures?
    (Springer, 2023-09-25) Robledano Aymerich, F.; Jimenez Franco, M. V.; Calvo Sendin, J. F.; Ecología e Hidrología
    Local biodiversity monitoring is important to assess the effects of global change, but also to evaluate the performance of landscape and wildlife protection, since large-scale assessments may buffer local fluctuations, rare species tend to be underrepresented, and management actions are usually implemented on local scales. We estimated population trends of 58 bird species using open-population N-mixture models based on count data in two localities in southeastern Spain, which have been collected according to a citizen science monitoring program (SACRE, Monitoring Common Breeding Birds in Spain) over 21 and 15 years, respectively. We performed different abundance models for each species and study area, accounting for imperfect detection of individuals in replicated counts. After selecting the best models for each species and study area, empirical Bayes methods were used for estimating abundances, which allowed us to calculate population growth rates (λ) and finally population trends. We also compared the two local population trends and related them with national and European trends, and species functional traits (phenological status, dietary, and habitat specialization characteristics). Our results showed increasing trends for most species, but a weak correlation between populations of the same species from both study areas. In general, local population trends were consistent with the trends observed at national and continental scales, although contrasting patterns exist for several species, mainly with increasing local trends and decreasing Spanish and European trends. Moreover, we found no evidence of a relationship between population trends and species traits. We conclude that using open-population N-mixture models is an appropriate method to estimate population trends, and that citizen sciencebased monitoring schemes can be a source of data for such analyses. This modeling approach can help managers to assess the effectiveness of their actions at the local level in the context of global change.
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    Trophic consequences of introduced species: Comparative impacts of increased interspecific versus intraspecific competitive interactions
    (Wiley-Blackwell, 2018) Britton, J. Robert; Ruiz Navarro, Ana; Verreycken, Hugo; Amat Trigo, Fátima; Didáctica de las Ciencias Experimentales
    1. Invasive species can cause substantial ecological impacts on native biodiversity. While ecological theory attempts to explain the processes involved in the trophic integration of invaders into native food webs and their competitive impacts on resident species, results are equivocal. In addition, quantifying the relative strength of impacts from non-native species (interspecific competition) versus the release of native conspecifics (intraspecific competition) is important but rarely completed. 2. Two model non-native fishes, the globally invasive Cyprinus carpio and Carassius auratus, and the model native fish Tinca tinca, were used in a pond experiment to test how increased intra- and interspecific competition influenced trophic niches and somatic growth rates. This was complemented by samples collected from three natural fish communities where the model fishes were present. The isotopic niche, calculated using stable isotope data, represented the trophic niche. 3. The pond experiment used additive and substitutive treatments to quantify the trophic niche variation that resulted from intra- and interspecific competitive interactions. Although the trophic niche sizes of the model species were not significantly altered by any competitive treatment, they all resulted in patterns of interspecific niche divergence. Increased interspecific competition caused the trophic niche of T. tinca to shift to a significantly higher trophic position, whereas intraspecific competition caused its position to shift towards elevated δ13C. These patterns were independent of impacts on fish growth rates, which were only significantly altered when interspecific competition was elevated. 4. In the natural fish communities, patterns of trophic niche partitioning between the model fishes was evident, with no niche sharing. Comparison of these results with those of the experiment revealed the most similar results between the two approaches were for the niche partitioning between sympatric T. tinca and C. carpio. 5. These results indicate that trophic niche divergence facilitates the integration of introduced species into food webs, but there are differences in how this manifests between introductions that increase inter- and intraspecific competition. In entirety, these results suggest that the initial ecological response to an introduction appears to be a trophic re-organisation of the food web that minimises the trophic interactions between competing species.