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Ferns are known to have a lower incidence of mycorrhization than angiosperms. It has been suggested that this results from carbon being more limiting to fern growth than nutrient availability, but this assertion has not been tested yet. In the present study, we took advantage of a fertilization experiment with nitrogen and phosphorus on cloud forest plots of the Ecuadorean Andes for 15 years. A previous analysis revealed changes in the abundances of fern species in the fertilized plots compared to the control plots and hypothesized that this might be related to the responses of the mycorrhizal relationships to nutrient availability. We revisited the plots to assess the root‐associated fungal communities of two epiphytic and two terrestrial fern species that showed shifts in abundance. We sampled and analyzed the roots of 125 individuals following a metabarcoding approach. We recovered 1382 fungal ASVs, with a dominance of members of Tremellales (Basidiomycota) and Heliotales (Ascomycota). The fungal diversity was highly partitioned with little overlap between individuals. We found marked differences between terrestrial and epiphytic species, with the latter fundamentally missing arbuscular mycorrhizal fungi (AMF). We found no effect of fertilization on the diversity or relative abundance of the fungal assemblages. Still, we observed a direct impact of phosphorus fertilization on its concentration in the fern leaves. We conclude that fern–fungi relationships in the study site are not restricted by nutrient availability and suggest the existence of little specificity on the fungal partners relative to the host fern species. [ABSTRACT FROM AUTHOR]

It is largely unknown how South America's Andean forests affect the global carbon cycle, and thus regulate climate change. Here, we measure aboveground carbon dynamics over the past two decades in 119 monitoring plots spanning a range of >3000 m elevation across the subtropical and tropical Andes. Our results show that Andean forests act as strong sinks for aboveground carbon (0.67 ± 0.08 Mg C ha−1 y−1) and have a high potential to serve as future carbon refuges. Aboveground carbon dynamics of Andean forests are driven by abiotic and biotic factors, such as climate and size-dependent mortality of trees. The increasing aboveground carbon stocks offset the estimated C emissions due to deforestation between 2003 and 2014, resulting in a net total uptake of 0.027 Pg C y−1. Reducing deforestation will increase Andean aboveground carbon stocks, facilitate upward species migrations, and allow for recovery of biomass losses due to climate change. Here, the authors investigate the aboveground carbon sink efficiency of Andean forests. The study shows the high potential of these forests to serve as future carbon refuges, and urges to reduce deforestation and increase restoration. [ABSTRACT FROM AUTHOR]

Summary: Anthropogenic atmospheric deposition can increase nutrient supply in the most remote ecosystems, potentially affecting soil biodiversity. Arbuscular mycorrhizal fungal (AMF) communities rapidly respond to simulated soil eutrophication in tropical forests. Yet the limited spatio‐temporal extent of such manipulations, together with the often unrealistically high fertilization rates employed, impedes generalization of such responses.We sequenced mixed root AMF communities within a seven year‐long fully factorial nitrogen (N) and phosphorus (P) addition experiment, replicated at three tropical montane forests in southern Ecuador with differing environmental characteristics. We hypothesized: strong shifts in community composition and species richness after long‐term fertilization, site‐ and clade‐specific responses to N vs P additions depending on local soil fertility and clade life history traits respectively.Fertilization consistently shifted AMF community composition across sites, but only reduced richness of Glomeraceae. Compositional changes were mainly driven by increases in P supply while richness reductions were observed only after combined N and P additions.We conclude that moderate increases of N and P exert a mild but consistent effect on tropical AMF communities. To predict the consequences of these shifts, current results need to be supplemented with experiments that characterize local species‐specific AMF functionality. [ABSTRACT FROM AUTHOR]

General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century. [ABSTRACT FROM AUTHOR]

Background:Biodiversity is perceived to decline from lowlands towards mountain peaks and away from the Equator towards the Poles, but supporting data for most groups of organisms are lacking, especially at the local scale. Aims:Elevational gradients of fern species richness in tropical forest habitats were analysed to test the hypotheses that fern species composition patterns were similar between elevational gradients, that total species richness of complete elevational gradients gradually declined due to changing climatic conditions with increasing distance from the Equator, and that the elevation of highest species richness gradually declined with increasing latitude. Methods:We used plot-based elevational fern species richness surveys compiled from recent field work and own published studies, between 18° N and 18° S along the Andean mountain range, and compared the transects of patterns of species richness and composition, and distribution of taxa. Results:Taxonomic composition was highly similar among tropical regions. Elevational richness patterns were symmetrically hump-shaped and overall richness was virtually equal along most of the tropical latitudinal gradient. In contrast, the subtropical localities at the edges of our study area, ca. 18° N and 18° S, showed strikingly different patterns from those in the tropical zone. Conclusions:Within the tropics, there appears to be no latitudinal diversity gradient of ferns at the local scale. We suggest that, in tropical habitats, species richness of ferns at the local scale is limited by the number of species that can co-occur and that the available niche space is saturated. [ABSTRACT FROM AUTHOR]

A land-cover classification is needed to deduce surface boundary conditions for a soil-vegetation-atmosphere transfer (SVAT) scheme that is operated by a geoecological research unit working in the Andes of southern Ecuador. Landsat Enhanced Thematic Mapper Plus (ETM+) data are used to classify distinct vegetation types in the tropical mountain forest. Besides a hard classification, a soft classification technique is applied. Dempster-Shafer evidence theory is used to analyse the quality of the spectral training sites and a modified linear spectral unmixing technique is selected to produce abundancies of the spectral endmembers. The hard classification provides very good results, with a Kappa value of 0.86. The Dempster-Shafer ambiguity underlines the good quality of the training sites and the probability guided spectral unmixing is chosen for the determination of plant functional types for the land model. A similar model run with a spatial distribution of land cover from both the hard and the soft classification processes clearly points to more realistic model results by using the land surface based on the probability guided spectral unmixing technique. [ABSTRACT FROM AUTHOR]

Texture information from passive remote sensing images provides surrogates for habitat structure, which is relevant for modeling biodiversity across space and time and for developing effective ecological indicators. However, the applicability of this information might differ among taxa and diversity measures. We compared the ability of indicators developed from texture analysis of remotely sensed images to predict species richness and species turnover of six taxa (trees, pyraloid moths, geometrid moths, arctiinae moths, ants, and birds) in a megadiverse Andean mountain rainforest ecosystem. Partial least-squares regression models were fitted using 12 predictors that characterize the habitat and included three topographical metrics derived from a high-resolution digital elevation model and nine texture metrics derived from very high-resolution multi-spectral orthophotos. We calculated image textures derived from mean, correlation, and entropy statistics within a relatively broad moving window (102 m × 102 m) of the near infra-red band and two vegetation indices. The model performances of species richness were taxon dependent, with the lowest predictive power for arctiinae moths (4%) and the highest for ants (78%). Topographical metrics sufficiently modeled species richness of pyraloid moths and ants, while models for species richness of trees, geometrid moths, and birds benefited from texture metrics. When more complexity was added to the model such as additional texture statistics calculated from a smaller moving window (18 m × 18 m), the predictive power for trees and birds increased significantly from 12% to 22% and 13% to 27%, respectively. Gradients of species turnover, assessed by non-metric two-dimensional scaling (NMDS) of Bray-Curtis dissimilarities, allowed the construction of models with far higher predictability than species richness across all taxonomic groups, with predictability for the first response variable of species turnover ranging from 64% (birds) to 98% (trees) of the explained change in species composition, and predictability for the second response variable of species turnover ranging from 33% (trees) to 74% (pyraloid moths). The two NMDS axes effectively separated compositional change along the elevational gradient, explained by a combination of elevation and texture metrics, from more subtle, local changes in habitat structure surrogated by varying combinations of texture metrics. The application of indicators arising from texture analysis of remote sensing images differed among taxa and diversity measures. However, these habitat indicators improved predictions of species diversity measures of most taxa, and therefore, we highly recommend their use in biodiversity research. [ABSTRACT FROM AUTHOR]