Florian Hofhansl

Tropical Ecosystem Research


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Presentation at AGU 2019 fall meeting, San Francisco, USA

IIASA researchers have participated in the American Geosciences Union Fall Meeting 2019 presenting research on climate adaptation and impacts on global ecosystems

Background: Tropical plant communities exhibit extraordinary species richness and functional diversity in highly heterogeneous environments. Albeit the fact that such environmental filtering shapes local species composition and associated plant functional traits, it remains elusive to what extend tropical vegetation might be able to acclimate to environmental changes via phenotypic plasticity, which could be a critical determinant affecting the resistance and resilience of tropical vegetation to projected climate change.

Methods: Based on a dataset compiled from 345 individuals and comprising 34 tropical tree species we here investigated the role of phenotypic plasticity versus non-plastic variation among key plant functional traits, i.e. wood density, maximum height, leaf thickness, leaf area, specific leaf area, leaf dry mass, nitrogen and phosphorus content. We hypothesized that trait variation due to plasticity is driven by environmental variability independently of spatial effects due to geographic distance between forest stands, whereas non-plastic variation increases with geographic distance due to adaption of the plant community to the local environment. Based on these hypotheses we partitioned total observed trait variation into phenotypic plasticity and neutral components and quantified respective amount of variation related to environmental filtering and neutral community assembly.

Results: We found that trait variation was strongly related to spatial factors, thus often masking phenotypic plasticity in response to environmental cues. However, respective environmental factors differed among plant functional traits, such that leaf traits varied in association with light regime and soil nutrient content, whereas wood traits were related to topography and soil water content. Our results further suggest that phenotypic plasticity increased with the range size of congeneric tree species, indicating less plasticity within range restricted endemics compared to their widespread congeners.

Conclusions: Differences in phenotypic trait plasticity affect stress tolerance and range size of tropical tree species, therefore endemic species could be especially prone to projected climate change.

Check out the link to the website including a link to the e-poster: https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/501085


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The role of plant functional trait variation in tropical forests

Evaluating the role of plant functional trait variation in tropical forests we found that environmental controls and different trait components, such as phenotypic plasticity, genetic adaptation and random factors differed between neotropical tree species and plant tissues. Results suggest that leaf traits varied in association with light regime and soil nutrient content, whereas wood traits were related to topography and soil water content. We furthermore found that phenotypic plasticity increased with the range size of congeneric tree species, indicating less plasticity within range restricted endemics compared to their widespread congeners. Our findings indicate that differences in phenotypic trait plasticity affect stress tolerance and range size of tropical tree species, and therefore suggest that endemic species could be especially prone to projected climate change.

Click on the poster to enlarge or download following the link below.

Check out the e-poster at the conference meeting website: https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/501085


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Amazon forest response to CO2 fertilization dependent on plant phosphorus acquisition

New study published in Nature Geoscience reports first modelling results from the exciting CO2-fertilisation experiment conducted in the middle of the Amazon

Current climate models suggest that trees will continue to remove manmade greenhouse gas emissions from the atmosphere, making it possible to stay within the targets set by the Paris Agreement. A study led by an international team of scientists however indicates that this uptake capacity could be strongly limited by soil phosphorus availability. The authors note that how the ecosystem reacts – whether trees will be capable of getting additional phosphorus from the soil through enzymatic processes or by forming more roots and symbiotic interactions that can provide scarce nutrients – must be further investigated. One thing is however certain, tropical rainforests are not an infinite CO2 sink and the Amazon forest reservoir must be preserved. This comes in line with response to rising international criticism over a surge in forest clearing since the beginning of the year, Brazilian President Jair Bolsonaro and officials in his administration have recently stepped up attacks on scientists at the country’s National Space Research Institute (INPE) for continuing to report transparently on deforestation in the Amazon.

Check out the press release and media attention for the article published in Nature Geoscience, August 2019.


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International Trait School – Porquerolles (France), 19-24 May 2019

In May 2019, I took the great opportunity to participate in the 8th edition of the graduate thematic course, sponsored by CNRS, France and the Centre for Forest Research, Quebec Centre for Biodiversity Science. It was one of the best ecological experiences of my scientific life so far and I would definitely recommend to anyone interested in plant ecology (see website for applications and some impressions of this edition below).

Also check out some of the islands incredible trail running routes and annual trail running events (https://www.hyeres-tourisme.com/agenda-fetes-manifestations/trail-de-porquerolles/).



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Permakultur – Dein Garten. Deine Revolution.

Die Permakultur orientiert sich an den Regeln der Natur. Und damit ist sie nicht allein. Wer entdeckt wie genial die Natur wirklich ist muss sich förmlich etwas von ihr abschauen. Doch was können wir noch alles von der Natur lernen.

Permakultur ist ein großes miteinander: Beziehungen, Netzwerke, Systeme, Kooperationen, “das Leben, das Universum und der ganze Rest” (laut Douglas Adams Autor des gleichnamigen Fantasy-Romans). Die Autorin erklärt diese Zusammenhänge in Ihrem Buch und zeigt wie diese Erkenntnisse in der Permakultur umsetzbar sind. Mit einem Gast-beitrag von Florian Hofhansl.

Link zum Buch: https://www.loewenzahn.at/buecher/2650/permakultur-dein-garten-deine-revolution/


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Beta diversity and oligarchic dominance in the tropical forests of Southern Costa Rica

Our article entitled “Beta diversity and oligarchic dominance in the tropical forests of Southern Costa Rica” was recently published in the journal Biotropica doi.org/10.1111/btp.12638.

Forest community assembly is shaped by environmental factors and stochastic processes, but so far the contribution of oligarchic species to the variation of community composition (i.e., beta diversity) remains poorly known. We established 1‐ha permanent inventory plots in humid lowland tropical forests of southwestern Costa Rica to identify oligarch species characterizing changes in community composition among forest types. Based on this network of forest plots we investigate how community composition responds to differences in topography, successional stage, and distance among plots for different groups of species (all, oligarch, common and rare/very rare species). From a total of 485 species of trees, lianas and palms recorded in this study only 27 species (i.e., 6%) were nominated as oligarch species. Oligarch species accounted for 37% of all recorded individuals and were present in at least half of the plots. Plant community composition significantly differed among forest types, thus contributing to beta diversity at the landscape scale. Oligarch species was the component best explained by geographical and topographic variables, allowing a confident characterization of the beta diversity among tropical lowland forest stands.

Please see this link to the online version of the article.