Natural History of Ecological Restoration

Tag: forest

  • ACCIÓN SERRANA Network: Conserving and restoring cloud forests in the mountains of Córdoba  province, central Argentina.

    ACCIÓN SERRANA Network: Conserving and restoring cloud forests in the mountains of Córdoba  province, central Argentina.

    By: Pablo Friedlander and Romina Torre

    Dr. Pablo Friedlander, Director of Acción Serrana has initiated and led pioneering restoration and intercultural education projects in Argentina, Brazil and Spain for more than two decades. He also organizes ethnobotanical research and expeditions to the Amazon and the Andes. pablofriedlander@gmail.com

    Biologist Romina Torre is the executive coordinator of Acción Serrana, with ten years of  experience in mountain restoration, research and educational activities involving rural communities, health practitioners and scientific institutions at bioregional and international levels. torre.romina@gmail.com

    Introduction to the Polylepis forests

    In the highest mountains of South America, remnants of vast stands of so-called cloud forests dominated by members of the beautiful Rose-family genus Polylepis are found throughout the Andes Cordillera, from Colombia and Venezuela to northern Chile and northwestern Argentina. In addition, in the much older Sierras Grandes de Córdoba, in central Argentina, the endemic Polylepis australis (locally known as Tabaquillo), occurs in scattered fragments of once extensive mid-altitude forests. At the continental scale, the canopies of these open, moist formations,  or what remains of them today, comprise 45 recognized species and constitute the highest altitude forests on Earth (Boza Espinoza & Kessler 2022). Sadly, their range and integrity has been drastically reduced by logging, burning, and overgrazing since the 16th century, especially with the introduction of European cattle.Their moss- and lichen-covered branches collect fog, while their roots prevent erosion and regulate water runoff. These forests also contribute to climate change mitigation,  by favoring carbon sequestration, and they support diverse endangered species dependent on these habitats. In all seven of the Andean countries where they occur, the restoration and conservation of these cloud forests is of vital importance to local communities and to protect. the headwaters of the main rivers and creeks (del Campo & Friedländer 2023).

    This locally famous ‘Grandfather’ Tabaquillo (Polylepis australis) tree grows in the heart of one of the last remaining cloud forest fragments in Córdoba  province.
    The Argentina anole, Pristidactylus achalensis, is an endemic lizard of the Pampa de Achala.

    The hand-shaped Polylepis leaves and the soft, multi-layered bark of the trees, draped with epiphytes, mosses and lichens, collect fog and give rise to the compelling and accurate image of the forest “milking” the omnipresent mist and clouds. At a continental scale, these cloud forests when they are healthy and thriving contribute to the ‘biotic pump’ connecting the Andes- the Amazon-and the Atlantic Forest biomes (Beveridge et al. 2024) and regulating water and climate cycles and  reducing the risk and severitry of wildfires. The savannas and cloud forests The recent increase of forest fires in all biomes of South – and Meso- and North America – demands more strategic and intercultural, public-private coalitions to increase restoration areas and protection of basins at multiple spatial scales for present and future generations (Argañaraz et al. 2015; Argibay & Renison 2018). Additionally, Polylepis roots and their mutualistic microorganisms retain and enrich soils. They also provide a ‘framework’ for regenerating forest communities undergoing active or assisted restoration. Indeed, when mature, these emblematic forests harbour very high biodiversity, including many endemic species of epiphytic orchids, insects, birds and reptiles, and also provide a wide range of ecosystem services to people at multiple spatial scales. Finally, they have huge cultural significance, and by working in synergy with local communities we aim to introduce and sustain biocultural as well as ecological restoration.

    Conserving and Restoring the cloud forests with Acción Serrana and Acción Andina

    In 2002, the project “Milking the Clouds” (Ordeñando Nubes, in Spanish) was launched, along with other local grassroots initiatives. Then, after a long learning curve in restoration methods and typical pioneering struggles, the five interrelated projects gradually scaled up their ‘footprint’ and their impact to a bioregional level over the next decade and a half. A big step was taken in 2018 when, together with the ECOAN (Asociación Ecosistemas Andinos) and Global Forest Generation, Acción Serrana was set up as a hub including 5 different local organizations to help in the launching of  “Acción Andina” as a a new international ecocultural restoration consortium. In that context, Acción Serrana is now managed by the Fundación de Actividades Biosféricas as part of Acción Andina. 

    Currently working in Peru, Ecuador, Colombia, Bolivia, Chile and Argentina, with 23 member institutions, Acción Andina partners have planted more than 7 million Polylepis trees, of many different species, and this number is rising each year, as is the success rate of the plantings. In 2023, Accion Andina received the prestigious Earthshot Prize, and in 2024 we were named one of the 7 UN World Restoration Flagships for the UN Decade on Ecosystem Restoration 2021-2030. 

    Map of the 12 Acción Serrana restoration sites in the Sierras Grandes de Córdoba.

    The 12 biocultural restoration areas in the Sierras Grandes of Córdoba under Acción Serrana management add up, at the time of writing, to a total of 3,170 fenced hectares. 

    The reforestation and restoration campaigns are made possible by 65 permanent staff members and over 1,500 volunteers per year on average. To date, we have produced and planted more than 860, 000 Polylepis australis nursery-grown saplings in consecutive seasons (see https://ecohealthglobal.org/network-sites/accion-serrana-argentina/). All of these trees were grown from seeds collected locally in each of the planting areas managed by the five different partnering organizations or local implementing groups  For the 2024-2025 October 2024 to March 2025 planting season, 250,000 trees were propagated in the 29 plant nurseries we maintain, and at the time of writing most of the plantings have been very successful. Since 2023, Accion Serrana has been helping to replicate the same initiative in Northwestern Argentina, with the Project Arbol y Vida in Jujuy Province (in cooperation with various high-Andean communities) and the Germinar Project in Tucuman Province (working with Diaguita communities of the Tafi del Valle bioregion), advising on and synergizing actions and application of  techniques and strategies. In addition to this biocultural restoration, another critical line of work is our environmental education program being run in local schools and municipalities for more than a decade already.

    The ecosystems of Acción Serrana are Sub-Andean and Chaco serrano forests and grasslands (sensu Cabrera 1976), composed of seasonally dry forests or open woodlands with 4 different altitudinal belts in the central Argentina mountain ranges, Sierras Grandes de Córdoba (Giorgis et al. 2011). The land tenure of the areas under restoration inside the Provincial Watershed Reserve of Pampa de Achala, which consists of private landholdings subject to Provincial Management & Conservation plans, or  public protected áreas within the National Park Quebrada del Condorito. The numerous activities we carry out include: maintenance and fencing of new areas, native forest tree and shrub seed collection, construction and improvements of nurseries, germination of seedlings, transplanting of seedlings to reusable plastic forest tubes, high mountain transfer of seedlings to the planting areas and their planting in the intervention areas during the rainy season. We establish permanent plots for scientific monitoring and we support research carried out in the intervention areas. Workshops, public talks and training programs are also organized yearly to train and recruit more enthusiastic and qualified citizen restorationists for the work in the mountains.

    Acción Serrana team planting the native Polylepis australis of Córdoba province.

    Implementation of Acción Serrana with local partners in reciprocity

    We work to  generate ecological, economic, social and cultural sustainability by reaching agreements with landowners, communities, networks and institutions (municipalities of Mina Clavero and Villa de Las Rosas, the Ministry of Education of the Province of Córdoba, and others). 

    To help with the local matching needed to be part of the Acción Andina  initiative, Acción Serrana had set up the Ayni Plan (“ayni” meaning “reciprocity” in the quechua language of the Andes). Basically this implies the commitment to generate 30% of operating costs through specific fundraising campaigns and by other quantified means. For example the constant one of inviting the public to participate by donations of the costs required for producing a forest (25 trees under monitoring), a tree or a volunteering activity. Then we promote the reception of donations of funds, lands, tools, materials, vehicles, etc.. In addition, we encourage ecotourism with a schedule for each area: summer plantations and seeds, winter transplanting of seedlings and fencing of restoration areas. Acción Serrana aims to increase reciprocity and abundance also throughout the different courses and events both virtual and in-person, and some special community parties, with raffles, concerts, talks, video screenings, and promotion of crowdfunding campaigns. Currently we are running our international matching crowdfunder campaign with the help of the Treeangle Foundation from the United Kingdom, as we have done each year from 2012, to complete the mission of this season January 2024 – March 2025. (See video here.)

    In the years ahead, Acción Serrana will propagate and plant a wider variety of native trees and shrubs in pursuit of a Framework species approach to restoration such as that being tested by EHN partner Daniel Perez and his team in Caviahue, Patagonia (Perez et al. 2019; see also here and (here). As a new initiative, we aim to  deploy 30% of funds raised to reintroduction of multipurpose Neltuma (formerly Prosopis) species and other framework species in lower altitudes of the mountain system, and 70% to ongoing Polylepis restoration in the high mountains. This year, we have begun studying how to propagate the obvious additional choices of “framework species” namely Maiten (Maytenus boaria), Escalonia (Escallonia cordobensis) and Molle (Lithraea molleoides). 

    Escallonia cordobensis a formerly common shrub now considered key to restoration.
    Co-dominant Maytenus boaria and Polylepis australis ‘giants’.

    Next steps

    Following decades of reforestation and cloud forest restoration, we are working with Indigenous inhabitants in these mountains, including the Comechingones (Henia and Camiare tribes) and Sanavirones peoples, who have been historically marginalized. We are cultivating intercultural bridges (Rojas et al. 2025) in áreas like nursery propagation, environmental education, and llama and alpaca reintroduction and ancestral practices of weaving with camelid wool. This collaborative framework aims to integrate and restore  key zones around the Ansenuza Sea, Traslasierra Valley, Pampa Achala, and Pampa de Pocho. 

    In January 2025, Acción Serrana became a new member hub of the Ecological Health Network, following two fruitful visits from James Aronson. These visits facilitated knowledge sharing and collaboration, furthering our core purpose of scaling up watershed restoration, enhancing environmental education, and deepening intercultural collaboration for research projects. By integrating ecological, social, and economic perspectives and approaches, we aim to share our regenerative experiences across mountains, jungles, deserts and oceans within a quickly growing international network of networks. We are delighted to be part of this movement and consortium with a strong, clear set of values and shared purpose  – something we all need to cultivate in these critical times. As a meaningful next step of Acción Serrana, we look forward to participating in multi-site research projects based on the simultaneous monitoring and evaluation of a series of ecological and human health indicators in areas undergoing biocultural restoration protocols. Through these efforts, we are committed to enhancing ecosystem health and strengthening our relationship with nature, ensuring the longevity and health of Andean cloud forests and lower buffer zones of Chaco serrano forests -as well as the local communities living there for generations to come. 

    Learn more by watching these videos on Acción Serrana and the Biodiversity in Sierras Grandes de Córdoba.

    All images are from the archives of Acción Serrana.

  • Managing invasive common buckthorn (Rhamnus cathartica) in the Midwest US

    Managing invasive common buckthorn (Rhamnus cathartica) in the Midwest US

    Andrew Kaul is a Restoration Ecologist in the Center for Conservation and Sustainable Development at the Missouri Botanical Garden. Mike Schuster is a Researcher in the Department of Forest Resources at the University of Minnesota. 

    Removing invasive shrubs is a critical step in ecological restoration projects in many degraded forests and woodlands across the Eastern US. Invasive shrubs quickly spread and outcompete native plants, which leads to declines in plant species diversity and ecosystem functioning. By suppressing these aggressive non-native species, restoration efforts can promote the regeneration of native vegetation that provides habitat and food sources for local wildlife. Removing invasive shrubs also allows more sunlight to reach the forest floor, enabling the regeneration of native tree seedlings and understory plants. Establishing an understory community is necessary to conduct effective management with prescribed burns in fire-adapted systems.

    Rhamnus cathartica, also known as “common buckthorn” or “European buckthorn”, is one of the most aggressive invasive species in Eastern North American forests. This buckthorn species is a shrub/small tree originally native to Europe and Western parts of Asia, brought to North America in the 1800s, and planted as a hedge-forming species. Buckthorn biology and control have been studied extensively in recent years due to its significant ecological and economic impacts, particularly in the Midwest US.

    R. cathartica native range in Eastern Hemisphere (map from Kurylo et al. 2007).

    ​Many aspects of its growth and reproduction make buckthorn a successful invader.Buckthorn is dioecious (male and female flowers occur on separate individuals) and femalesproduce copious quantities of small berry-like fruits called drupes (like a cherry) that are widely dispersed by birds. Buckthorn can thrive in many soil and light conditions, being especially tolerant to low-light environments caused by shading from other trees and shrubs. It also has unique phenology, holding its leaves late into fall. Like many invasive shrubs, its dense branching physiognomy leads buckthorn to form thickets that shade out native vegetation, decreasing diversity of plant species in invaded forests. In addition to effects on plants, buckthorn invasion has also been linked to changes in soil chemistry and may increase soil erosion through reducing the cover of understory plants.

    ​R. cathartica non-native range as depicted by the Biota of North America Program (BONAP). Light blue denotes counties where buckthorn has been reported, and pink indicates where it is present and state-listed as a noxious weed. This map likely represents a conservative estimate of common buckthorn’s range, which has been expanding in recent years.

    Many of the same traits that make buckthorn a good invader also make it very difficult to remove and control when restoring natural areas. It produces extensive root systems that store nutrients, so it can re-sprout vigorously when cut. This means removal requires repeated control efforts over multiple years. The most common control methods used to manage buckthorn include mechanical and chemical treatments. Mechanically, young seedlings can be hand-pulled and saplings can be removed with a weed wrench. More mature plants are often girdled, cut, or mowed to remove most of the biomass, and then application of herbicide is necessary, otherwise, stems will survive and quickly re-sprout within only a few weeks. Herbicide can also be applied to basal bark without cutting, but this method is less effective on large individuals.

    Even with persistent effort, complete buckthorn control is rarely successful because it can quickly recolonize areas if not thoroughly removed. Fortunately, there is some good news about the feasibility of buckthorn management. It was previously believed that buckthorn seeds could form persistent “banks” in the soil, with seeds surviving for up to 6 or 7 years, waiting for the right set of conditions to trigger germination. However, our recent study showed that buckthorn seeds actually germinate in one to two years, with 97% germinating in the first year. This is a critical discovery for the management of buckthorn, as it indicates that after removing large individuals, management methods to suppress seedling establishment are key to preventing reinvasion. Moreover, if seedlings are suppressed for the first couple of years, then buckthorn control is possible. Because these fleshy-fruited invaders are so readily dispersed by birds, complete eradication is unlikely, but continued management can keep densities low enough to not impact native plant communities.

    R. cathartica seedlings forming a dense layer near the ground in a temperate deciduous forest in Eastern Minnesota USA (Photo by Andrew Kaul).

    ​Our research group at the University of Minnesota led by Peter Reich has been studying buckthorn for several years, funded by multiple grants from the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC). Recent work in our group has focused on how to suppress buckthorn regeneration after initial removal of large individuals. The Cover it up! project investigates which methods of revegetation are most effective for restoring the ground-layer with native species that can prevent buckthorn recruitment and growth. Various experimental introductions of native plants have included direct seeding shrubs, direct seeding trees, adding herbaceous seed mixes with variable ratios of grasses to forbs, and treatments with combinations of functional groups. For example, we combined sowing the Standard Cover It Up seed mix of 34 native grasses, and forbs with planting bare-root plants from other functional groups – trees, shrubs, ferns, or sedges.

    Across several experiments, one of the most important results has been that the extent to which revegetation treatments are effective in suppressing buckthorn, is mostly explained by their ability to rapidly establish vegetation, preempt space, and shade out buckthorn seedlings. Two of the most successful strategies include 1) planting native tree species and 2) seeding a mix of native Elymus spp. grasses (wild ryes) and wildflowers to establish an herbaceous understory. The native trees used in this experiment included species like Sambucus canadensis (elderberry), Abies balsamea (balsam fir), and Acer saccharum (sugar maple), planted immediately after clearing-out buckthorn. Planting woody native species can reduce buckthorn regrowth by up to 80%, and establishing a grassy herbaceous community can reduce regrowth by 77%.

    We recently published A Guide to Forest Understory Revegetation, which makes several science-based recommendations for invasive shrub management based on our research. Revegetation should occur as soon as possible after initial removal of large individuals. Additionally, restoring sites via revegetation will be most effective in areas with at least 10% open canopy so that sufficient light is present for native seedlings to establish. If opening the canopy is feasible by selectively removing some trees, this will facilitate a greater cover and diversity of herbaceous plants in the understory. When conducting revegetation with herbaceous species, planting a native seed mix with a high proportion of cool season (C3) grasses is ideal. These species grow well in shadier environments, establish rapidly, are inexpensive, and produce dense vegetation that can carry a fire to facilitate management with prescribed burns. Shade-adapted wildflowers such as Ageratina altissima (white snakeroot) or Hydrophyllum virginianum (Virginia waterleaf) should be included in the seed mix in order to add value to pollinators and other insects. When conducting revegetation with woody species, planting native tree species can be highly effective in excluding buckthorn, but revegetation through bare-root plantings has its drawbacks, being more expensive and labor intensive. This method would work well if implemented in smaller areas, especially where there are few deer. In general, revegetation plansshould prioritize reducing light reaching the ground where buckthorn seedling are growing.Counterintuitively, this can be achieved by opening the tree canopy to facilitate establishment of herbaceous cover in the understory. 

    In addition to studying methods of revegetation to suppress buckthorn seedlings, our research group is also investigating novel methods for removal of mature buckthorn plants. In June 2024, we initiated an experiment testing the efficacy of critical period cutting to kill large buckthorn without the use of chemicals. This method was pioneered by Friends of the Mississippi River (FMR) as a strategy for removing buckthorn without using herbicide, which is prohibited in Minneapolis parks. This method involves using a saw or loppers to cut off the top of a buckthorn plant about 1.5 m from the ground early in the growing season. Subsequently, a couple times throughout the growing season, each buckthorn is revisited and stripped (picked off easily by hand) of all re-growth. This process is then repeated the following year, if necessary. Cutting the stem at chest height rather than near the ground has multiple benefits of 1) reducing risk of stumps as a tripping hazard, 2) relocating previously cut stems, and 3) stripping re-sproutsthat usually occur at the end of the stem, which is near chest height.

    Given FMR’s success implementing the critical period cutting method, our experiment is examining when this method is most effective in killing buckthorn depending on the size of the individual or its light environment. We are also quantifying the minimal effort required to ensure buckthorn mortality by examining survival of buckthorn over two years of stripping re-sprouts, with 4, 6, or 10 total removals. To test how effective this method is for controlling other invasive shrub species, we are working with collaborators in Wisconsin, Maine, and Missouri, who are also conducing this experiment on the invasive shrubs Frangula alnus (glossy buckthorn) and Lonicera maackii (bush honeysuckle). These are also serious woody invaders of forests throughout the Midwest and our research aims to improve forest restoration outcomes at smaller scales when herbicide or other larger-scale methods are not possible.

    Stems of common buckthorn in a study area examining the efficacy of critical period cutting in Minnesota (Photo credit Alex Roth).
    Experimental stems of bush honeysuckle at the Missouri Botanical Garden’s Shaw Nature Reserve (Photos by Andrew Kaul). 

    If you are interested in learning about these projects in greater depth, you can read the guide to forest understory revegetation here or learn more about ongoing research in the Cover It Up! project here. If you have any questions, feel free to contact Mike (schuster@umn.edu) or Andrew (akaul@mobot.org).