Many forests in one forest: ecological dynamics and climate change in the Andean Araucanía
Trees growing on fallen trunks, shade-tolerant species emerging in lowland areas, and the effects of snow on plant mortality. For a decade, researchers have observed changes in permanent vegetation plots—or forest sampling units—in the Bosque Pehuén Nature Reserve, being surprised by the diversity of ecological processes and adaptations of species such as Nothofagus and araucaria. We spoke with ecologist and forestry engineer Ricardo Moreno, who co-led these studies with Iván Díaz.
A vegetation plot, understood ecologically, is a delimited area of the forest used to obtain a sample of plant composition, structure, and/or function at a given time. Long-term monitoring of these plots is a collective effort to understand changes in ecosystem conditions, even when there are no perceptible day-to-day movements, and to determine forest dynamics.
In Bosque Pehuén (BP) [1] , to date, there are eight plots of 1,000 m2 monitored since 2014. These plots are designed, established and monitored by our Foundation and researchers from the Biodiversity and Canopy Ecology Laboratory (LabDosel) of the Austral University of Chile (UACh) [2] . The monitoring is co-led by the ecologist and forest engineer, and associate researcher of the LabDosel of the UACh and the Calahuala Cooperative, Ricardo Moreno, with whom we spoke to address the impact of this study and its projections.
These permanent plots in BP are 20 x 50 m, and are established along an elevation gradient, where the objective is to understand the dynamics of mountain forests dominated by species of the genera Nothofagus [3] and Araucaria [4] . Dynamics that can be expressed in changes in composition, structure and function of the forest, from processes that could be linked to the effects of climate change in the absence of natural disturbances. In these more than 10 years of monitoring in permanent plots, various phenomena have been observed that have surprised researchers, such as the regeneration of tree species on standing trees that could provide advantages in their establishment, the recent development of shade-tolerant species where they were not previously found, or important changes in species composition in a relatively short time.
Mar Adentro Foundation (FMA): What would you say are the scientific foundations of a plot and what methodologies exist for its study?
Ricardo Moreno (RM): Plots represent a sample of a moment in a forest’s history and are one of the most common ways to measure a forest to obtain a representation of its composition and structure, among other things. For example, in our case, we were able to identify trees within the forest and understand the forest based on principles such as the number of species per unit area. This allowed us to estimate the plant population and individual changes in its health, among other variables. Scientific standards and techniques can often be judged as objectivations of nature, but they are a way of understanding, an approximation to knowledge. In this sense, a plot sheds light on the processes taking place in one territory and that can then be observed in others, which contributes to shaping that story. To ecologically interpret changes in a forest, an abstraction is made based on what it tells us at a predetermined moment. Regarding methodologies, there are international standards for the measurements and variables to observe. At BP, there are eight plots, five of them since 2014, then one was added in 2018 and two more in 2024. The idea was to describe what changed at different elevations, to project whether there were responses to climate change, given that at the time it was speculated that forests at a certain elevation were expected to rise—due to rising temperatures, among other factors—something we may be able to see in the coming years, but this response in other forests around the world has been controversial.
FMA: It’s been over a decade since the first plot was planted at BP. How significant is that period considering the years—or the ages of the trees—that have coexisted in this forest?
RM: The Pehuén Forest, like other mountainous areas in La Araucanía, has higher elevations that were not disturbed or exploited by the forestry companies or cattle ranching that proliferated in the 1960s. You could say it’s a more mature forest at higher altitudes and younger in the lower elevations. At the same time, there are some high elevations where fires have occurred, and there are younger areas there. In general, the young trees range in age from 40 to 80 years old, while some araucaria trees are as old as 100 years and can be close to 1,000 years old, approximately.
A decade is quite a short time for these forests, due to the longevity of the species. Some coigües and raulís, for example, can live up to 500 years, while araucaria trees can be thousands of years old. Thus, a period that may be quite long for humans is short for trees, but when regularly monitored over time, we can study how a place has changed and make decisions based on international standards. Proportionally, it’s as if we were trying to understand the life history of a 70-year-old person by studying their behavior over the past two years.
According to our results, a decade has not been enough time to observe structural changes at the tree level, but it has allowed us to observe changes at the understory level. The relative stability between birth/death rates and growth rates is also a very interesting response over these 10 years.
FMA: What conservation strategies and decisions can be made based on the study’s findings?
RM: While there’s no magic key to solve forest conservation problems, using forest dynamics or natural environment study methodologies, we observe climatic variables that go beyond our capacity to intervene and that are sometimes part of natural variation. What we can influence is to think of networks of private and public protected areas in constant communication, and not as static protection units isolated from one another. Species migrate independently of human boundaries, so an important path is to understand that what we are protecting may not be the same in the future. Right now, at this moment, we are safeguarding specific ecological and evolutionary processes that are beyond us as a species. In that sense, collaboration is important, for example, between BP and Villarrica National Park , where a narrative of the vegetation being protected in these two macro-units is being generated. However, I could imagine that the Araucaria trees would find it very difficult to migrate south due to the biogeographic barrier represented by the valleys, with their different climatic conditions and degraded and fragmented forests due to land-use changes.
FMA: There may come a point where the forest cannot continue to grow…
RM: Of course, and it is worrying if we consider that these species are growing on sorts of islands and that their migration capacity is restricted. There are strategies, such as assisted migration farming, that is, moving from one place to another. A valid strategy, but we must ensure that we do not alter the historical range of natural variation so much [5] , because we can generate ecological aberrations, as has occurred with Biological invasions that have transformed ecological conditions in unexpected ways. We must take into account the time window we are considering, as there are adaptive processes that we cannot predict, and that should be part of the discussion. Along these lines, strategies can be developed around practices in productive territories that cannot be left untouched, as we need to generate economic support, but that involve a certain level of management that facilitates adaptive processes. I mean that on properties that are not exclusively for conservation, producers can support migration processes or conservation strategies.
FMA: Returning to BP and the area where it is located – Andean Araucanía – what are the main threats facing native vegetation and what regeneration patterns have you found?
RM: One of the main threats is climate change, but it is difficult to address this through planning, as the effects are uncertain. Other threats are invasive species such as wild boar and the effect of browsing [6] by hares. There are some sour cherry and rosehip trees, non-native invasive plants that are concentrated along trails or where there are open spaces that have not recovered from previous disturbances. Although they were not recorded in the plots, we have also observed Oregon pine in areas where there is little vegetation cover near the araucaria forests, and in the event of fires, this would increase the available fuel biomass, affecting the araucaria and other native species.
Regarding tree regeneration, this is a variable process that we use to interpret ecological succession processes. Although continuous regeneration is not generally expected in Nothofagus-Araucaria forests, it is found in the Pehuen forest, perhaps due to the variation in the cover and density of the understory and canopy. In my opinion, plant reproductive biology (pollination, seeding, germination) is one of the best sensors we can observe in plants’ response to climatic events and/or trends or other types of disturbances, and therefore allows us to estimate their adaptive capacity or vulnerability. Therefore, it is important to have a finer temporal resolution, since they do not necessarily respond linearly to growth and may not be directly correlated with each other. That is, a year of good growth may not mean a large amount of pollen and pollinated flowers, or may not result in abundant regeneration. Reproductive biology is a complex annual phenomenon involving many related species (e.g., pollinators and dispersers) that requires consideration of the characteristics of each species. For example, herbaceous species with shorter life cycles, such as an orchid, were found during one period in the Pehuén forest and not the next, likely triggering changes in the cycles of other species.
One of the regeneration processes we have seen is that, given the lack of space in the canopy that lets in light, shade-tolerant species begin to appear at elevations where they were not found in previous periods. On the other hand, the regeneration of Nothofagus, which are shade-intolerant, confirmed the importance of fallen tree trunks in these forests, since regeneration occurred thanks to the greater height of the ground, with less shade. In previous monitoring, we identified a mechanism unknown in the world regarding the dynamics of gaps. This occurred because we found trees that grow above others and are not necessarily considered epiphytes [7] , some of which could even be more than 100 years old. In this study, led by Iván, it was postulated that plants could have a competitive advantage when they fall to the ground.
FMA: How would you describe the mortality rate and the integrity of the trees in Bosque Pehuén?
RM: They are two different things. There can be high mortality without affecting the integrity of the forest. All trees will die, as mortality is natural, but during the monitoring period we have seen that mortality is more frequent among young trees than among adults. What is happening in young forests, below 1,000 m elevation, is that there is an increase in dead trees over living ones, but this is natural. Many trees regenerate, but as with humans, not all of them reach 80 years of age or older. We don’t know the precise causes, but we suspect that in addition to a natural process of exclusion at this stage of forest life, snow could have also influenced mortality. Between 2015 and 2017, there was significant snowfall due to the El Niño phenomenon, which coincided with the increase in the mortality rate.
On the other hand, the lack of fires or other human-caused disturbances in recent years has favored regeneration processes and maintained the integrity of the young and adult forests of the Pehuen Forest. We can assess this integrity by the quantity and variety of forest structural elements that promote biodiversity, such as old trees with microcavities and trunks with varying degrees of decay. All of these elements are present in the different forests within the Pehuen Forest. In my opinion, the integrity of young forests is particularly relevant in the Pehuen Forest, which in many other places has been managed, thus altering the response to climate change or natural disturbances. Another element evaluated during monitoring was the growth rate, measured as changes in tree diameter between 2014-2018 and 2018-2024. Contrary to expectations, the growth rate remained the same or even increased in some plots despite the possible influence of the megadrought. This short-term response may also be an indicator of forest integrity, but we don’t know if it will have a subsequent effect.
FMA: What changes have occurred in plant diversity this decade?
RM: We’ve recorded variable responses in the number of species along the gradient. While two to three species decreased in some plots from 2014 to 2018, some were recorded again in the 2024 measurement. We have seen notable changes in abundance; for example, the colihue, which covered a good portion of the lower plots, decreased in 2018, but then increased again in 2024. The opposite occurred with dwarf cinnamon and smaller plants like the white luma. Each plot has different responses; some changed little from year to year, while others did vary. There have also been no determining directional changes in vegetation. The forest dynamics models are diverse.
FMA: Is it like there are many forests within a forest?
RM: Yes, and this is because there are very diverse possibilities. Species have different capacities to respond to climatic events or socio-natural disasters. It’s interesting to see altered physiological responses of species with snow cover, for example, which has decreased in depth. We want to know what will happen to snow-covered species adapted to certain conditions, like the dwarf cinnamon tree. Perhaps it will move higher. We must consider whether we want to encourage species to rise to resist climate change, in terms of conservation decisions.
FMA: In this regard, one of the relevant factors for the study has to do with the elevation gradient in relation to the effects of climate change. Could you elaborate on this connection?
RM: Climate change is causing many species to move to higher elevations in search of more suitable environments for their development. This shift, called “climate elevation,” significantly impacts the distribution and survival capacity of plants. Mountains are natural laboratories for evaluating how to respond to one scenario or another. On a global scale, it has been recognized that responses are at the species level, according to their specific characteristics; they do not necessarily involve the forest as a whole.
FMA: Technologies such as: Canopy Capture [8] How do you see the potential of these and new technologies in light of AI?
RM: This ties into one of the first questions about monitoring methodologies. Ecological studies sometimes use expensive instruments, but with the widespread use of smartphones, simple apps have been developed that provide accurate measurements. Scientifically, we’re talking about precise and biased measurements. In the case of the app you mention, if I always use the same phone to measure canopy cover with average light sensitivity, the result will be data with average precision but no bias. The opposite is true for humans, where inaccurate and biased data have little value. I mean, there’s no panacea in terms of technology or methodology, as there will always be some degree of error. For me, the important thing is to recognize the technological and methodological limitations of human beings, since we will always be limited in our understanding, as we perceive the world according to our capabilities or the technologies available at the time. AI could generate major changes, perhaps even some unintended ones. But it’s just another tool that requires oversight to avoid errors or biases. I’d like to see AI continue to facilitate some activities rather than worshipping these technologies as the ultimate goal.
FMA: On the other hand, the use of certain technological tools could tend to deepen extractive practices, while simultaneously facilitating conservation strategies. These are possibilities that coexist; some authors even speak of the ecological cyborg [9] …
RM: That’s an interesting, contradictory, and challenging idea. AI must be considered ethically to avoid widening social gaps or degradation due to extractive practices. For conservation, it’s important that information not only remain in a paper or article, but that it contribute to generating effective conservation strategies, generating mountain study networks as natural laboratories sensitive to ecosystem changes. I wasn’t familiar with the term “ecological cyborg ,” but I think it’s basically what describes an ecologist, where AI helps speed up this processing and makes it easier for data to generate correlations for the conservation and sustainable use of forests.
FMA: What would you say is the main result of this study in 10 years?
RM: There have been several surprises in relation to the expectations (hypotheses) we had based on the literature. We’ve observed that there is stability and instability in the forest at the same time, depending on how we observe it. This ambivalence in response varies from species to species and not necessarily at the scale of the forest as a whole. Furthermore, in the absence of natural disturbances, there are factors that have an important impact, as much or more than temperature or precipitation, and which I would love to continue exploring; I’m referring to snow, something I didn’t see so clearly before delving deeper into this mountain ecosystem.
About the interviewee: Ricardo Moreno holds a PhD in Ecology and Biodiversity and a degree in Forestry Engineering. His work combines botany, forestry, paleoecology, and conservation to explore how forests evolve and adapt to climate change and natural or human disturbances. His career has taken him from lush tree canopies to uncovering environmental history through paleoecology. By monitoring long-term changes, delving into canopy biodiversity, or collaborating with communities, he explores ways to integrate science and conservation. He is particularly interested in plant adaptability to global change, their uses, and sustainable management.
Reference:
[1] Protected area and natural laboratory managed by the Mar Adentro Foundation.
[2] The LabDosel work team is composed of: Ricardo Moreno, Ivan Diaz, Constanza Flores, Rocio Burgos, Nicolas Segovia, Camila Figueroa, Joaquin Espinoza, Scarlett Arzola.
[3] The genus Nothofagus is a group of tree plants that make up a significant part of temperate and southern forests, with a Gondwanan origin dating back some 45 million years. The species of this genus in Bosque Pehuén are coigües, raulíes, oaks and lengas.
[4] An ancient species endemic to the temperate forests of South America (Chile and Argentina). In Bosque Pehuén, there are specimens that are about 700 years old.
[5] It refers to the evolution or biological process when it is left to its natural course, without human intervention .
[6] Herbivorous diet.
[7] Species that grow on top of each other. There are three groups: orchids, ferns and bromeliads or quiches.
[8] Which measures the percentage of canopy cover.
[9] The metaphor is from ecologist Carlos Martínez del Río (2009), who refers to an organism that combines the observation skills of a scientist, the passion of a naturalist and the technical insight of a robot, as noted in the book Ecology and Observation: Broadening the Scope of Science to Understand a Complex World by Rafe Sagarin and Aníbal Pauchard.