Tropical montane ecosystems, including montane forests, are relatively little studied, but they are home to significant biodiversity and provide important ecosystem services, such as water supply and participation in the regulation of temperature and regional and global climate. The available data on mountain vegetation and its dynamics are far from what is needed to confidently simulate 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 Great Britain, sheds light on these questions. An effective way to bridge this gap, the paper’s authors argue, would be to create “an interdisciplinary network” capable of studying the natural dynamics of mountain ecosystems and their responses to drivers of global change locally, regionally and at 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 modelling, 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 mountain ecosystems with the aim of quantifying the hitherto neglected role of these ecosystems in the carbon and water cycle as well as other ecosystem services.” Laszlo Karoly Nagy first author of the article, said.
Nagy is a professor at the State University of Campinas (UNICAMP) in the state of São Paulo, Brazil, and coordinator of the long-term ecological research project in Campos do Jordão State Park (PELD-PECJ), also in the state of São Paulo. His contribution to the study was supported by FAPESP.
The final 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 UK’s science and research funding agency.
Tropical montane ecosystems of South America
Tropical forests in mountainous areas more than 1,000 meters above sea level vary from wet, like the 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 Andean valleys between ridges.
Mountain vegetation includes both forest and non-forest. Tree growth is limited at high altitudes and low temperatures, but climate change will alter the structure and function of these ecosystems. The Andes have e.g. many montane forest areas, but the current rate of warming is 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 the land use has been 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 function 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 ecosystems in South America, cataloging and synthesizing existing knowledge for use in future modeling of these sites’ contribution to regional and global carbon/water cycles. .
“The selection of the areas must be stratified on the basis of climate and biogeography, taking into account the historical and cultural context of land use,” said Nagy. “All this shows the diversity of situations that must be analyzed in socio-ecological terms, so that the available knowledge can be synthesized and find a way to the construction of a wide-ranging project.”
Method
The study included eight sites in the Andes and southeastern Brazil: the Venezuelan, Colombian, and western Ecuadorian Andes; the Amazon-Andes transect in Peru; the mountains of northwestern 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 changes in vegetation and the associated biological and hydrological cycles. in response to climate change for decades to come.
Tree biomass data were available for six sites. The researchers carried out 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 parameterisation and calibration. This analysis identified a temperature-related decrease in montane forest net primary production, respiration and allocation to aboveground biomass, as well as an increase in soil carbon stocks with elevation.
One of the difficulties for researchers in these regions is obtaining data to identify the transition between montane forest and non-tree alpine vegetation. “If we combine modelers and field scientists who know the forest, we can decide what works for each participant, identify the special characteristics and see how they can talk to each other. It is most important for the two communities to interact so that the results are produced by modeling can be checked against empirical data,” Nagy said.
Next steps will include continued development of models with Ibero-American colleagues, including Brazilians, and three European groups of modelers. All of these groups work at different scales, including the global scale adjusted for mountains and landscape, which may include 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 limiting photosynthesis.”
Right now, he added, the work involves bringing together the various actors, including a network of socio-ecological observatories for the Andes (ROSA), under construction, and defining the sites to be investigated in the next phase of the project.
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