Bryophytes have been proposed as ideal indicators of ecosystem change, because they are important components of forest integrity, and considerable research indicates that some groups are sensitive to ...the changes associated with specific human disturbances. Bryophyte richness and abundance have been found to vary predictably along elevational gradients, but the role of human impacts on these distribution patterns remains unclear. The aim of this study is to explore the impact of human disturbance on the elevational patterns of bryophyte diversity, along an elevational gradient. Along the gradient we collected three datasets in the following sites: preserved (P), forest track roadsides (R) and disturbed by agriculture/silviculture practices (D). Two survey plots of 100 m2 were established at every 200 m elevational step for each sites P, R, D, and in each plot bryophytes were sampled in a stratified manner. At each plot we recorded all species on available substrates and estimated their percentage cover. Our results showed that species number did not differ among studied sites, but that species diversity pattern differs among the three gradient types and species life strategy composition along the elevational gradient showed a clear response to the disturbance of mature communities. We conclude that human impact has strongly changed the elevational pattern of diversity, and that these changes vary depending on the ecological and taxonomical group considered.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aim
How spatial, historical and ecological processes drive diversity patterns remains one of the main foci of island biogeography. We determined how beta diversity varies across spatial scales and ...among organisms, disentangled the drivers of this variation, and examined how, consequently, biogeographic affinities within and among archipelagos vary among land plants.
Location
Macaronesia.
Taxon
Bryophytes, pteridophytes, spermatophytes.
Methods
Species turnover and nestedness were compared within and among archipelagos across taxonomic groups. The relationship between species turnover and nestedness, climatic, geological and geographic factors was analysed using generalized dissimilarity models.
Results
Species turnover, but not nestedness, increased with the geographic scale. This increment decreased from spermatophytes, pteridophytes and bryophytes, wherein the median turnover was less than half that in spermatophytes. Bryophytes exhibited a significantly higher nestedness and lower turnover than spermatophytes. Extant climatic conditions and island age contributed the most to all models but the importance of island age for bryophyte and pteridophyte turnover was marginal. Spermatophyte floras clustered by archipelago, whereas the clustering patterns in pteridophyte and bryophyte floras reflected macroclimatic conditions.
Main Conclusions
The lower increment of species turnover with spatial scale and the higher nestedness in bryophytes and pteridophytes than in spermatophytes reflect the variation in dispersal capacities and distribution ranges among land plants. Accordingly, extant climatic conditions contributed more to explain turnover in bryophytes and pteridophytes than in spermatophytes, whereas factors associated with dispersal limitations, including island age, geographic distance and archipelago structure, exhibited the reverse trend. The differences in beta diversity patterns, caused by different responses of Macaronesian land plant lineages to the main factors shaping their community composition, explain their different biogeographic affinities. These differences reflect a distinct origin and different mechanisms of speciation among Macaronesian land plant lineages and archipelagos.
The European rabbit (Oryctolagus cuniculus) is a pest and a conservation problem on many islands, where its heavy grazing pressure threatens many endemic plants with extinction. Previous studies in ...its native and introduced range have highlighted the high spatial variability of rabbit abundance at local and landscape scales, depending on many factors such as the existence of different habitats. Modeling of the species can be useful to better understand spatial patterns and to prioritize actions, especially in those regions in which rabbits have become invasive. Here, we investigate the distribution of the European rabbit in Tenerife (Canary Islands, Spain), where the species was introduced during the 15th century and has subsequently changed vegetation composition. Added to the direct effects of rabbits on vegetation, climate change could also have implications for rabbit populations, especially in the alpine ecosystem. To evaluate that, we estimated rabbit abundance in 216 plots randomly distributed on Tenerife island (61 in the alpine ecosystem), modeled the potential current spatial abundance of the species and considered how it might vary under different climate change scenarios. We associated rabbit abundance to a wide selection of abiotic, biotic, and human variables expected to influence rabbit abundance on the island. We found a positive correlation between rabbit abundance and temperature and a negative correlation in the case of precipitation. Hence, according to the models’ projections, climate change is expected to enhance rabbit populations in the future. Current higher densities were related to land disturbance and open areas, and a remarkable increase is expected to occur in the alpine ecosystem. Overall, we consider that this study provides valuable information for land managers in the Canary archipelago as it reveals how global warming could indirectly exacerbate the conservation problems of the endemic flora in oceanic islands.
Climate change is causing major changes in terrestrial ecosystems and biomes around the world. This is particularly concerning in oceanic islands, considered reservoirs of biodiversity, even more in ...those with a significant altitudinal gradient and high complexity in the vegetation they potentially harbour. Here, in Tenerife (Canary Islands), we have evaluated the changes in potential vegetation belts during the last 20 years by comparing them with a previous study. Considering the intimate linkage between vegetation and climate, we used a methodology based on phytosociological knowledge, ordination techniques and geostatistics, using multivariate spatial interpolations of bioclimatic data. This has allowed us to spatially detect the variations experienced by eight vegetation units during the last 20 years and incorporating a set of vulnerability metrics. New bioclimatic and vegetation cartography are provided according to the current scenario studied (1990–2019). Our results indicate that summit vegetation, humid laurel forest and thermo-sclerophyllous woodland are the habitats that have experienced a very high area loss and mismatch index, strong changes, if we consider that we are only comparing a period of 20 years. Simultaneously, the more xeric vegetation belts, the dry laurel forest and the pine forest would have benefited from this new warmer and drier climate, by gaining area and experiencing strong upward movements. These changes have not been spatially uniform, indicating that the elevational gradient studied not explain completely our results, showing the influence of the complex island topography. Effective landscape management should consider current remnants, transition capacity and movement limitations to better understand current and future vegetation responses in a global change context.
The recurrence of fires has increased considerably due to human activity, affecting even forests where traditionally fire is uncommon. In this study, we verify the effects of degradation caused by ...fire in the Canarian laurel forests, which is a subtropical forest formation restricted to the humid montane areas of these Macaronesian islands. We evaluated the effect of fire by comparing a series of burned plots corresponding to fires from 1960, 1984, 1995, to 2012 with geographically proximate and comparable unburned plots in the Garajonay National Park (La Gomera Island, Spain). We focused on three aspects that are immediately altered by fire: forest structure, floristic composition, and microclimate. These aspects have been quantified using (a) tree density, the Pielou index using tree height classes, and DBH for the vertical structure of the forest; (b) DCA, the Bray Curtis dissimilarity index, and a species indicator analysis for the floristic composition; and (c) temperature and relative humidity for microclimate under three canopy cover conditions. Our results reveal that, overall, structural complexity and its composition in the burned areas have barely reached 40% and 35%, respectively, when compared with unburned areas, and recovery mainly depends on time since fire. Additionally, burned plots presented more pioneer species, a higher density of trees, and climatic variables tend to have a wider range throughout the day. These data reveal the long time span that this ecosystem needs for recovery to a prefire state and how it may be more prone to subsequent fire events.
The monitoring of ecosystems and forests is an urgent requirement in the current framework of global change. It is particularly necessary on oceanic islands where their rich biodiversity is highly ...vulnerable, with many narrow-ranged endemic species. Quantifying and mapping forest health through key ecological variables are essential steps for management, but it will also be challenging and may require a lot of resources. Remote sensing has the potential to be a very useful tool to assess the development and conservation status of forests. We assessed the applicability of the light detection and ranging (LiDAR) on the laurel forests of La Gomera, making allometric equations for various measurements of the forest structure, linking field inventory from 2019 and 2017 LiDAR data through standard linear regressions. Decision trees and logistic regressions were also used to assess the performance of LiDAR in the recognition of young-growth and old-growth laurel forests. The obtained allometric models were a good fit in general and their predictions were in line with already known data. Likewise, decision tree and logistic regression to distinguish young-growth and old-growth forests had a similar performance in both cases, with a high to medium-high degree of accuracy. Therefore, LiDAR was revealed to be a useful tool for the monitoring of the laurel forest by the managers.
Climate change may shift species outside of their current climatic tolerances, which can be problematic for oceanic islands with limited options for species migration. Their alpine habitats, which ...represent islands within islands, are a special concern due to high endemism rates. The Canary Islands have two examples for such fragile ecosystems above 2000 m, on La Palma and Tenerife. This study contributes an assessment of the Canary Islands’ climatic habitat for 47 alpine plant species under observed climate change (1959–1989 versus 1990–2019 periods) as well as for future projections (2041–2060 and 2061–2080 periods). We analyzed the contraction of climatic habitats and migration requirements (biotic velocity) for each species to compensate for observed and predicted climate change. Our results suggest that temporary climate refugia exist on Tenerife but are insufficient on La Palma, where habitat loss due to historical climate change has already created an area of significant concern: the Cumbre Vieja Natural Park. On Tenerife, current alpine species can find suitable climate habitats in the caldera area and on the Teide-Pico Viejo volcano. That said, migration paths toward these refugia are long and complex, and human-assisted migration may be required. Species-specific statistics to support such management interventions are provided in this study.
Ecosystems that provide environmental opportunities but are poor in species and functional richness generally support speciation as well as invasion processes. These processes are expected not to be ...equally effective along elevational gradients due to specific ecological, spatial, and anthropogenic filters, thus controlling the dispersal and establishment of species. Here, we investigate speciation and invasion processes along elevational gradients. We assess the vascular plant species richness as well as the number and percentage of endemic species and non‐native species systematically along three elevational gradients covering large parts of the climatic range of La Palma, Canary Islands. Species richness was negatively correlated with elevation, while the percentage of Canary endemic species showed a positive relationship. However, the percentage of Canary–Madeira endemics did not show a relationship with elevation. Non‐native species richness (indicating invasion) peaked at 500 m elevation and showed a consistent decline until about 1,200 m elevation. Above that limit, no non‐native species were present in the studied elevational gradients. Ecological, anthropogenic, and spatial filters control richness, diversification, and invasion with elevation. With increase in elevation, richness decreases due to species–area relationships. Ecological limitations of native ruderal species related to anthropogenic pressure are in line with the absence of non‐native species from high elevations indicating directional ecological filtering. Increase in ecological isolation with elevation drives diversification and thus increased percentages of Canary endemics. The best preserved eastern transect, including mature laurel forests, is an exception. The high percentage of Canary–Madeira endemics indicates the cloud forest's environmental uniqueness—and thus ecological isolation—beyond the Macaronesian islands.
Ecological, anthropogenic, and spatial filters control plant richness, diversification, and establishment of non‐native species on the oceanic island La Palma. Increase in ecological isolation with elevation likely drives diversification and thus above average numbers of endemics at high elevations. We argue that unsuitable environmental conditions and lower human influences are responsible for the absence of non‐native species at elevations above 1200 m.
Islands have traditionally been considered as migratory and evolutionary dead ends for two main reasons: island colonizers are typically assumed to lose their dispersal power, and continental back ...colonization has been regarded as unlikely because of niche preemption. The hypothesis that islands might actually represent dynamic refugia and migratory stepping stones for species that are effective dispersers, and in particular, for spore-producing plants, is formally tested here, using the archipelagos of the Azores, Canary Islands, and Madeira, as a model. Population genetic analyses based on nuclear microsatellite variation indicate that dispersal ability of the moss Platyhypnidium riparioides does not decrease in the island setting. The analyses further show that, unlike island populations, mainland (southwestern Europe and North Africa) populations underwent a severe bottleneck during the last glacial maximum (LGM). Our results thus refute the traditional view of islands as the end of the colonization road and point to a different perception of North Atlantic archipelagos as major sources of biodiversity for the postglacial recolonization of Europe by spore-producing plants.
Questions: We addressed three questions: (1) what is the variation of α- and β-diversity of bryophyte communities across spatial scales in an elevational gradient; (2) is spatial variation ...characteristic of different phylogenetic (mosses/liverworts) and/or ecological groups (terrestrials/epiphytes); and (3) what is the contribution of species richness and species replacement (true turnover) to β-diversity along the elevational gradient? Location: La Palma, Canary Islands, Spain. Methods: An elevational transect spanning 0–2200 m a.s.l was sampled at altitudinal intervals of ca. 200 m, two 10 m × 10 m plots were established at each elevation and inside each plot three 2 m × 2 m quadrats were randomly selected. Within each quadrat, bryophytes were sampled in three replicate microplots of 10 cm × 5 cm, for each substrate: soil, rocks, leaves, humus, decaying wood and tree trunks at three heights. We evaluated α- and β-diversity at plot and elevational level for all bryophytes and for phylogenetic and ecological groups. Values of β-diversity were further decomposed into replacement and richness differences. We tested the relationship between α- and β-diversity and elevation using linear models with and without a quadratic term (elevation2) in an AICc-based framework. Results: A total of 121 species were recorded along the transect. Alpha-diversity showed a hump-shaped pattern with elevation for all bryophytes, liverworts and epiphytic species, however, terrestrial species and mosses displayed no clear pattern. Species replacement was the main driver of β-diversity for all bryophytes and also for mosses and terrestrial species, and at different scales (elevational belt and quadrat). The contribution of species replacement increased with elevation, except for epiphytes and terrestrials. Conclusions: Our study contributes towards an understanding of the spatial organization of bryophyte diversity at different scales along an insular elevational gradient. We showed that bryophyte diversity was mostly influenced by species replacement at the largest scale. The observed differences in β-diversity decomposition between bryophyte phylogenetic and ecological groups could be dependent on climatic conditions and substrate availability. The strong differences observed along the elevational gradient related to true turnover are especially important in the current global change scenario.
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