Florian Hofhansl

Tropical Ecosystem Research


LACOSA – Landscape-scale controls on Aboveground forest Carbon stocks along environmental gradients on the OSA peninsula, Costa Rica

Albeit the fact that tropical forests store large amounts of carbon (C) in aboveground tree biomass, the mechanistic controls on forest C stocks remain poorly resolved. To date, one of the key factors limiting our current knowledge of tropical forest ecosystem responses to projected environmental changes (such as increasing atmospheric CO2, increasing temperatures and prolonged drought periods) is the lack of a mechanistic understanding of how the controlling state factors (e.g. climate, geology, time and biota) determine the distribution of aboveground C stocks at the landscape-scale. Here, we aim at unraveling the mechanistic links between environmental controls such as edaphic factors (i.e. soil type, topographic position) and climatic drivers (i.e. temperature, precipitation), and demographic parameters (species composition and vegetation structure) and how they determine tropical aboveground C stocks at the landscape-scale. To that end, we will be investigating species composition and vegetation structure of >10.000 tree individuals that have been mapped and identified in 20 one-hectare plots established across edaphic and topographic gradients on the OSA peninsula, Costa Rica.


Based on this unique data set we aim to identify relationships between plotbased measurements of soil parameters (i.e. texture and chemistry) and high-resolution data on tropical vegetation structure (i.e. maximum tree diameter, total tree height and crown indices) derived from terrestrial laser scanning. As a result, we opt to resolve spatial patterns of tree species composition and vegetation structure associated with landscape-scale gradients of environmental drivers and thus create a mechanistic understanding of how these factors shape the distribution of aboveground C stocks in tropical forest ecosystems that could be extrapolated in future scenarios.

Project Update: https://tropicalbio.me/2017/03/03/lacosa-project-update/

Amazon FACE – “Experiment in the Amazon forest will test the reaction to global warming”

Will global warming provide a solution to one of the problems it creates? To find an answer to this intriguing question, a team of scientists started investigations for what may be the most ambitious experiment the Amazon forest has seen in some 20 years. Ecologists are hoping the project, called Amazon FACE (Free-Air CO2 Enrichment), can tell them whether the forest will survive the drought that global warming is expected to cause.


Further Reading: http://www.labterra.net.br/en/amazon-face_en/ – Project Homepage: https://www.inpa.gov.br/amazonface/

COBIGA – “The Biological Corridor La Gamba (COBIGA)”

The COBIGA is part of the Osa Biological Corridor. The focus of the project lies mainly on the connection of the lowland forests of the Piedras Blancas National Park with the “Fila Cal”, a largely unprotected area covered with mountain rainforests. The exchange of species of the lowland and mountain forests is thus facilitated and contributes to an enrichment of the flora and fauna in both ecosystems. Furthermore, the Fila Cal is an important transition corridor zone to the Talamanca mountains to the north. On the basis of aerial photographs taken in 2003 (CARTA 2003), particularly important prospective corridor areas were identified. Special importance was attached to (1) the closing of forest gaps in order to create a continuous forest area as far as possible, and (2) the reforestation or restoration of pastures and/or river banks for water protection and the formation of ± compact corridors. At present, most of the envisaged sites are in private hands and the farmers first need to be convinced of the corridor idea. Recently, the Austrian association “Rainforest of the Austrians” has taken an active part in the COBIGA project and engages mainly in purchasing selected, promising corridor lands, and in restoring and reforesting them. There are many benefits to a reforestation project such as this one. Along with the reforestation of an area, forest carbon storage areas are also enlarged and safe zones for the dispersal of fauna and flora species are created. Such areas become central reservoirs for common and endangered species and also allow us to create study areas for future research. Reforestation projects also provide opportunities for collaboration on solving social issues, such as providing jobs directly and indirectly for the community of La Gamba.


Project Funding: Verein zur Förderung der Tropenstation La Gamba, Costa Rica. Project Homepage: http://www.lagamba.univie.ac.at/

BDEF – “Biodiversity and Ecosystem Functions – Landscape and climate controls of biodiversity and ecosystem processes in tropical rainforests of SW Costa Rica”

In the course of this project we established 20 one-hectare plots in two regions in the South-West of Costa Rica (Piedras Blancas National Park, and Reserva Forestal Golfo Dulce and nearby regions on the Peninsula Osa). These regions are comparable in terms of altitude, geology, geomorphology, and soils, but differ in climate. Therefore the comparison of ecosystems at both sites permits to discern landscape and climatic effects on biodiversity and ecosystem processes in ecosystems of different climatic sensitivity. After defining most important ecosystem types for both regions, we chose five replicate plots per ecosystem type. Based on recent remote sensing data forest plots were established in ecosystems from primary undisturbed rainforests to secondary forests (15-25 years old) stocking on abandoned pasture or agricultural land, differing in topography. In respective one-hectare plots we evaluated biodiversity (tree species, microbial community composition) and ecosystem processes (i.e. primary productivity, stem increment, litterfall, leaf area index, soil chemical parameters and soil respiration).


Project Funding: Austrian Federal Ministry of Science and Research (BMWF). Project Homepage: http://www.univie.ac.at/bdef

MICDIF – “Linking microbial diversity and functions across scales and ecosystems”

MICDIF is a National Research Network (NRN) within the Priority Research Programme of the Austrian Research Fund FWF. Fourteen scientist out of 10 different institutions in Austria and Switzerland conduct 8 individuals projects (IPs). The project aims at elucidating the significance of microbial diversity on ecosystem functioning by explicit coupling of microbial ecology and community structure to biogeochemistry. Despite considerable advances in biodiversity research during the past decade, which primarily dealt with plants and animals, there is an urgent need to further develop the functional role of microbial biodiversity in ecosystems.


Project Funding: Austrian Science Fund (FWF). Project Homepage: http://www.univie.ac.at/micdif

EcoCatch – “Understanding the effects of global change on ecosystem processes and services at catchment scale”

EcoCatch investigates local inputs of N, P, S, K+, Ca2+, Mg2+, H+; Corg via wet and dry deposition for the associated UNECE International Cooperative Programme “Integrated Monitoring of Air Pollution Effects on Ecosystems“. Between 2008-2010 we set-up and monitored various devices including wind, air temperature and air humidity sensors, a fog collector, rain gauges, sensors for soil moisture and soil temperature, litter traps, suction cups, ground water sampling tubes at different ground water levels, xylem sap-flow measurement units on trees for the collection and processing of water samples in fog, rainfall, throughfall, stem runoff, soil water, ground water and surface run-off. The stable isotopic composition of hydrological samples was measured by gas chromatography, elemental analysis isotope-ratio mass spectrometry and laser absorption spectroscopy and we finally developed an isotope-mixing model incorporating data on 18O and 2H that was presented at the 9th Austrian Stable Isotope User Group Meeting, Innsbruck, Austria.


Project Funding: Government of Lower Austria and Clean Air Commission, Austrian Academy of Sciences (KRL – ÖAW). Project Homepage: http://www.oeaw.ac.at/krl/projekte/EcoCatch_en.htm

CostaRica – “Carbon and element cycling in a tropical lowland forest, Costa Rica: Inter-annual variability and climate coupling”

This project focuses on controls of seasonal and interannual fluctuations in nutrient cycling and primary production of a primary rainforest. To study the differences in net primary production (NPP) in relation to (i) land-use history, (ii) topography, and (iii) interannual climate changes, three forest sites were selected in the Esquinas Forest (“Regenwald der Österreicher”), Piedras Blancas National Park, Corcovado, Costa Rica, in February 2005. The Esquinas forest is located at the Southern Pacific slope of Costa Rica, with a mean annual temperature of 28 °C and a mean annual precipitation of 6000 mm. Twelve small plots (à 0.01 ha) were established within each forest type, i.e. primary ridge forest, primary ravine forest and secondary ravine forest, and topography as well as species distributions were recorded. Climate, forest microclimate, litter fall, stem increment growth, root production, precipitation-throughfall-stemflow and associated nutrient fluxes, litter decomposition and soil respiration are studied.


Project Funding: Commission for Interdisciplinary Ecological Studies, Austrian Academy of Sciences (KIÖS – ÖAW). Project Homepage: http://www.oeaw.ac.at/kioes/prob/costarica_e.htm