Secondary forests more sensitive to drought than primary forests
The dry summer of 2018 hit Swedish forests hard - and hardest affected were the managed secondary forests. This according to a new study from Lund University in Sweden.
Northern boreal forest ecosystems are predicted to experience more frequent summer droughts in the future. The majority of Swedish forest are secondary forests that are managed commercial forests with little diversity in species and structure. Only a small part is made up of primary forests that have experienced limited direct human impact.
So far, it has not been known how primary forests and managed secondary forests react to drought. In a new study published in the scientific journal Environmental Research Letters, a team of researchers led from Lund, analysed how the drought of 2018 affected the forest types.
“We used a unique map of primary forests in Sweden and investigated whether there might be any difference in how these forests and neighbouring secondary forests were affected by the drought in 2018. The results showed that secondary forests in Sweden were more affected by the drought than primary forests were,” says Anders Ahlström, researcher in physical geography at Lund University.
In the study, researchers used satellite images and a map detailing more than 300 primary forests in Sweden. By analysing a high-resolution vegetation index over these and the buffer zones surrounding the primary forests, which represent secondary forests with a similar environment and drought situation in summer 2018, the research team were able to gain a picture of how the dry summer hit the different forest types.
“That primary forests were less affected by drought leads to a number of interesting follow-up questions about what causes this difference. It could be the trees’ generally greater age and size that perhaps leads to deeper roots and more structural diversity. Or it could be that there is more water in these ecosystems, perhaps because they haven’t been ditched. Right now though, we have no idea what makes primary forests more stable during drought,” says Julika Wolf, former physical geography researcher, now a consultant on cartography and spatial analysis.
Primary forests are rare in Sweden and in Europe. They represent the most untouched forests we have left, and they inform us of how nature looks and how it functions without major direct human impact. The forests, therefore, are especially important in understanding how environmental changes and human land use affect ecosystems and their processes.
“This study is a good example of how we can use these primary forests in our research. In this case, we see that they are more stable during drought when compared with secondary forests that have been exposed to change such as felling, planting, ground preparation and ditching.” concludes Anders Ahlström.
JOURNAL
Environmental Research Letters
ARTICLE TITLE
Canopy responses of Swedish primary and secondary forests to the 2018 drought
Study proposes refinement of models to project ecosystem services in montane forests
Modeling projections depend on the installation of networks specific to these areas in Brazil and the Andes, where the available data falls far short of what is needed.
IMAGE: MODELING PROJECTIONS DEPEND ON THE INSTALLATION OF NETWORKS SPECIFIC TO THESE AREAS IN BRAZIL AND THE ANDES, WHERE THE AVAILABLE DATA FALLS FAR SHORT OF WHAT IS NEEDED view more
CREDIT: LASZLO KAROLY NAGY
Tropical mountain ecosystems, including montane forests, are relatively little studied, yet they are home to significant biodiversity and provide important ecosystem services, such as water supply and participation in regulation of temperature and regional and global climate. The data available on mountain vegetation and its dynamics falls far short of what is needed to simulate with confidence its interaction with the atmosphere in response to climate change.
A new study published in the journal Plant Ecology & Diversity by a group of scientists affiliated with universities in Brazil and several other South American countries, as well as the United Kingdom, casts light on these questions. An effective way to bridge this gap, the authors of the article argue, would be to create “a transdisciplinary network” capable of studying the natural dynamics of mountain ecosystems and their responses to global change drivers locally, regionally and across the continent, within the framework of a socio-ecological system.
“The results of our research show that very little information of the kind needed to model mountain clusters in South America is available. We need more specific data to do this modeling, especially if we want to include socio-ecological diversity. We advocate the creation of a network of sites representing the heterogeneity of social and ecological conditions in montain ecosystems with the aim of quantifying the hitherto neglected role of these ecosystems in carbon and water cycling, as well as other ecosystem services,” Laszlo Karoly Nagy, first author of the article, told.
Nagy is a professor at the State University of Campinas (UNICAMP) in São Paulo state, Brazil, and coordinator of the Long-Term Ecological Research Project in Campos do Jordão State Park (PELD-PECJ), also in São Paulo state. His contribution to the study was supported by FAPESP.
The last author was Stephen Sitch, Chair in Climate Change at the University of Exeter, whose contribution was supported by the Natural Environment Research Council (NERC), part of UK Research & Innovation (UKRI), the United Kingdom’s science and research funding agency.
Tropical montane ecosystems in South America
Tropical forests in mountainous areas more than 1,000 meters above sea level vary from wet, like Serra do Mar in Brazil, for example, or parts of the Andes adjacent to the western Amazon Basin, to seasonally dry, like the Atlantic Rainforest biome or the Andean inter-ridge valleys.
Mountain vegetation comprises both forest and non-forest. Tree growth is limited at high altitudes and low temperatures, but climate change will alter the structure and functioning of these ecosystems. The Andes has many montane forest areas, for example, but current rates of warming there are three times higher than in other parts of South America, and temperatures in the region are expected to rise as much as 6 °C by the end of this century.
South America’s mountains also have large non-forest areas where land use has changed to agriculture and pasture. In this context, the subtropical and tropical mountains of South America are a high priority for projecting the impact of future climate on the structure and functioning of these ecosystems in terms of climate feedback and potential use of ecosystem services.
In the study, which was based on a workshop held in Campinas, the researchers analyzed a network of mountain ecosystem sites in South America, cataloging and synthesizing existing knowledge for use in future modeling of these sites’ contribution to regional and global carbon/water cycles.
“Selection of the areas has to be stratified on the basis of climate and biogeography, taking into consideration the historical and cultural context for land use,” Nagy said. “All this shows the diversity of situations to be analyzed in socio-ecological terms so that the available knowledge can be synthesized and a pathway found for the construction of a wide-ranging project.”
Methodology
The study covered eight sites in the Andes and Southeast Brazil: the Venezuelan, Colombian and west Ecuadorean Andes; the Amazon-Andes transect in Peru; the mountains of northwest Argentina; Cape Horn in Chile; and Serra da Mantiqueira and Serra do Cipó in Brazil.
Only two of these (one in Venezuela and the other in Brazil) had climate, ecological and ecophysiological data that could be used as parameters for dynamic global vegetation models (DGVMs), computer programs that simulate shifts in vegetation and the associated biological and hydrological cycles in response to climate change for decades ahead.
Tree biomass data was available for six sites. The scientists performed a preliminary assessment using a DGVM known as JULES (Joint UK Land Environment Simulator) to look for gaps in available data and their impact on model parameterization and calibration. This analysis identified a temperature-related decrease in montane forest net primary production, respiration, and allocation to above-ground biomass, as well as an increase in soil carbon stocks with elevation.
One of the difficulties for researchers on these regions is obtaining data to identify the transition between montane forest and non-arboreal alpine vegetation. “If we combine modelers and field researchers who know the forest, we can decide what works for each participant, identify the peculiarities, and see how they can talk to each other. It’s most important for the two communities to interact so that the results produced by modeling can be checked against empirical data,” Nagy said.
Next steps will include continuing the development of models with Ibero-American colleagues, including Brazilians, and three European groups of modelers. All these groups work at different scales, including the global scale adjusted for mountains and landscape, which can encompass land use.
“Mountain characteristics require a specific approach,” he said. “For example, you should analyze how tree growth is limited in terms of plant tissue production versus limitation by photosynthesis.”
Right now, he added, the work entails bringing together the various actors, including a network of socio-ecological observatories for the Andes (ROSA), under construction, and definition of the sites to be studied in the next stage of the project.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
JOURNAL
Plant Ecology
ARTICLE TITLE
South American mountain ecosystems and global change – a case study for integrating theory and field observations for land surface modelling and ecosystem management
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